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  • Life and Medical Sciences  (30,791)
  • Aircraft Propulsion and Power
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  • 1
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    Preliminary Computational Assessment of Disk Rotating Detonation Engine Configurations (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-14
    Description: A rotating detonation engine (RDE) configuration whereby the working fluid enters and exits in a predominantly radial manner is examined using a quasi-two-dimensional computational fluid dynamic simulation. The simulation, based on a Cartesian coordinate system, was originally developed to examine the physics and performance of the more typical annular RDE. Modifications required to accommodate the radial and circumferential flowfield are discussed. The centripetal forces that arise in this disk RDE (DRDE) configuration create a different wave structure than that seen in the annular RDE. They also give rise to markedly different fluid behavior depending on whether the flow is radially inward or radially outward. Using an entropy-based measure of pressure gain, it is found that for the preliminary idealized calculations performed in this paper, the inward flowing DRDE outperforms the outward flowing variant. The inward flowing DRDE is further shown to outperform the equivalent annular RDE. The effects on performance of several parameters are examined, including inner-to-outer diameter ratio, inner-to-outer cross-sectional area ratio, and inlet throat-to-channel area ratio.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA 2020-2157 , GRC-E-DAA-TN75670 , AIAA Scitech 2020 Forum; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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    NASA TECHNICAL REPORTS
  • 2
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    AQUIFER Nano-Electrofuel Energy Economy and Powered Aircraft Operations (2020)
    In:  CASI
    Details
    Publication Date: 2020-01-22
    Description: The Aqueous, QUick-charging battery Integration For Electric flight Research project is explained and the major subsystems are described, including nano-electric fluid, rim-driven motors, and integration concepts. The nano-electric fluid concept is a new type of aqueous flow battery that could reduce or retire the fire and explosion hazards of conventional batteries and fuel cells. The nano-electric fluid itself could enable energy storage and increased available energy per fuel weight ratios. The rim-driven motor is being developed to improve propulsion system safety and stability and to reduce noise. The rim-driven motor concept could enable motors that are more efficient both electrically and aerodynamically. The Energy Economy of the project concept is presented as a potential renewable or green energy sustainment for utilizing in-place infrastructure. The nano-electric fluid energy charge-use-recharge cycle is presented using renewable energy input from solar, wind, and hydroelectricity. Powered aircraft operations are presented, and the logistics of the new nano-electric fluid technology are explored. Powered aircraft operations topics include weight and balance, fueling, recharging, safety, and derivative considerations.
    Keywords: Aircraft Propulsion and Power
    Type: AFRC-E-DAA-TN74097 , SciTech Forum; Jan 06, 2020 - Jan 10, 2020; Orlando, FL; United States
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  • 3
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    Experimental Investigation of a One-Sided Ejector Nozzle (2019)
    In:  CASI
    Details
    Publication Date: 2019-05-07
    Description: A fundamental exploratory experiment is conducted assessing the performance of a one-sided ejector with the eventual goal of noise reduction for jet engines. The hardware is comprised of an 8:1 rectangular nozzle together with an ejector box whose lower surface is flush with the lower lip of the nozzle. Secondary flow is allowed through a gap between the upper lip of the nozzle and a flap that constitutes the upper surface of the ejector. Wall static pressures and Pitot probe surveys are conducted to evaluate the performance of the ejector with variation of geometric parameters. It is found that addition of vortex generating tabs at the upper lip of the nozzle significantly increases secondary flow entrainment. The entrainment is further enhanced by a divergence of the ejector upper surface. Limited noise measurements are done. The baseline ejector (without tabs) often encounters flow resonance with accompanying tones. The tabs have the additional benefit of eliminating those tones in all cases. However, for the tabbed case, addition of the ejector produces insignificant further noise reduction. This is due to the fact that the flow remains unmixed on the lower half of the ejector. The focus of ongoing and future efforts is to achieve sufficient mixing of the flow so that the exhaust velocities are uniformly low, while keeping the ejector hardware short and lightweight.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220064 , GRC-E-DAA-TN65186 , E-19654
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  • 4
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    Computation Simulations of Electric Propulsion Aircraft: The X-57 Maxwell (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-03
    Description: Outline - Introduction: X-57 CFD task overview; Motivation. Part I, Computational simulations without propulsion: Establishing CFD (Computational Fluid Dynamics) Best Practices - Grid generation - Mesh refinement study - Numerical methods - Wind tunnel validation study; Power-Off Aerodynamic Database Results. Part II, Computational simulations with propulsion: Cruise Power-On Database; High-Lift Power-On Database. Summary.
    Keywords: Aircraft Propulsion and Power
    Type: ARC-E-DAA-TN69863 , NASA Advanced Supercomputing Advanced Modeling & Simulation (AMS) Seminar Series; Jun 13, 2019; Moffett Field, CA; United States
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  • 5
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    Geared Turbofan Engine Having a Reduced Number of Fan Blades and Improved Acoustics (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A rotor blade comprises an airfoil extending radially from a root section to a tip section and axially from a leading edge to a trailing edge, the leading and trailing edges defining a curvature therebetween. The curvature determines a relative exit angle at a relative span height between the root section and the tip section, based on an incident flow velocity at the leading edge of the airfoil and a rotational velocity at the relative span height. In operation of the rotor blade, the relative exit angle determines a substantially flat exit pressure ratio profile for relative span heights from 75% to 95%, wherein the exit pressure ratio profile is constant within a tolerance of 10% of a maximum value of the exit pressure ratio profile.
    Keywords: Aircraft Propulsion and Power
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  • 6
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    Development of a Broadband Acoustic Emulator to Mature Propulsion Noise Reduction (CFANS-BB) (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A simulator to artificially generate turbofan broadband signatures using the ANCF (Advanced Noise Control Fan) test article is presented. [Development of a Broadband Acoustic Emulator to Mature Propulsion Noise Reduction (CFANS-BB: Configurable Fan Artificial Noise Source- Broadband)]
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN67362 , Acoustics Technical Working Group (ATWG) Spring 2019 Meeting; Apr 10, 2019 - Apr 12, 2019; Hampton, VA; United States
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  • 7
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    Numerical Investigation of a Shielded Chevron Nozzle (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Reynolds-Averaged Navier-Stokes simulations have been performed on a three-stream inverted velocity profile nozzle with and without various configurations of chevrons attached. The nozzle was mounted on a planform to imitate an engine mounted above a wing, shielding ground observers from engine noise. Several chevron designs intended to aggressively mix the jet and move noise sources upstream for shielding were examined to investigate there effects on noise and thrust. Numerical results for the baseline nozzle and one chevron configuration were compared with far-field noise and particle image velocimetry data obtained in NASA Glenn Research Center's Aero-Acoustic Propulsion Laboratory. A configuration in which chevrons alternate penetration into the primary stream and tertiary fan stream was explored using the Modern Design of Experiments approach. Short, high-penetration chevrons demonstrated a significant noise reduction for a relatively small thrust penalty.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2019-220066 , E-19656
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  • 8
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    Multipoint Design and Optimization of a Turboshaft Engine for a Tiltwing Turboelectric Vertical Takeoff Landing Air Taxi (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: This paper describes the design of a turboshaft engine for a tiltwing air taxi application. In this case, the tiltwing air taxi is intended to fly a 400 nm mission with up to fifteen passengers. Engine requirements for the concept engine are taken from aircraft system studies where thrust is produced by four propellers driven by electric motors and powered by a single gas turbine engine. The purpose of this paper is to perform a cycle design optimization that minimizes fuel consumption and weight while respecting current technology limitations to meet mission requirements. To achieve results, the engine overall pressure ratio and maximum temperature at the exit of the combustor are set as the design parameters. Several sensitivity studies are also performed to visualize optimization trends. Results of the optimization study show solutions are heavily dependent on engine cooling flow requirements and exact mission requirements. This engine is intended for use in large system optimization research.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220151 , AIAA Paper 2019-1948 , E-19671 , GRC-E-DAA-TN65425 , AIAA SciTech Forum 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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  • 9
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    Computational Modeling for Non-Equilibrium Shock Tube Flows (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-25
    Description: Time accurate simulation of non-equilibrium flows inside shock tube facilities presents several challenges from both physical and mathematical aspects. Furthermore, the large computational cost makes it impractical to support a real-time experimental test campaign. In this work, we explore other methods for modeling the shock tube problem with the main focus on the post-shock region and the absolute radiation emanating from it. The proposed alternative approach is several orders of magnitude less computationally expensive while still accurate enough with regards to the quantities of interest. Excellent agreement is found with the established stagnation-line approach. Comparison with time-accurate simulations shows good agreement close to the peak values and disagreement of the temperatures relaxation and radiance profiles toward equilibrium.
    Keywords: Aircraft Propulsion and Power
    Type: ARC-E-DAA-TN70861 , International Symposium on Shock Waves (ISSW32); Jul 14, 2019 - Jul 19, 2019; Singapore; China
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  • 10
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    Lessons Learned in Fabrication of a High-Specific-Torque Concentric Magnetic Gear (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Magnetic gearing is being investigated at NASA as a replacement to conventional mechanical gearing in aerospace applications. Some potential benefits of magnetic gears over mechanical gearing are torque transmission without mechanical contact, decreased transmission noise, and no required lubrication. However, in order to be a viable alternative for aerospace applications, magnetic gearing must be shown to provide high enough specific torque (torque per unit mass). NASA's second magnetic gearing prototype (PT-2) was able to achieve promising specific torque on par with low torque mechanical gearboxes. This work will briefly review the electromagnetic and structural design of PT-2, provide detailed information on fabrication and assembly, examine build errors, walk through rebuild efforts to improve operation, and conclude with remarks on build difficulties and opportunities for improvement in future prototypes.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN68518 , Annual Vertical Flight Society (VFS 2019) Forum and Technology Display (Forum 75); May 13, 2019 - May 16, 2019; Philadelphia, PA; United States
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  • 11
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    NASA Acoustic Stirling IRAD Thermal Recovery Energy Efficient System (TREES) Energy Conversion and Management in Aircraft (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA Acoustic Stirling IRAD (Internal Research and Development) Thermal Recovery Energy Efficient System (TREES) Energy Conversion and Management in Aircraft. Presentation on energy conversion on aircraft. Thermal energy recovery changes aircraft thermal management from being a necessary burden on aircraft performance to a desirable asset. It improves the engine performance by recycling waste heat and ultimately rejecting all collected aircraft heat out through the engine nozzle.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN68025 , Interagency Advanced Power Group (IAPG 2019) Mechanical Working Group (MWG) Meeting; May 14, 2019 - May 16, 2019; Houston, TX; United States
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  • 12
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    Modeling Turboshaft Engines for the Revolutionary Vertical Lift Technology Project (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Turboshaft engine performance and weight models were developed to support conceptual propulsion and vehicle mission design in support of the National Aeronautics and Space Administration's (NASA) Aeronautics Mission Research Directorate's (ARMD) Revolutionary Vertical Lift Technology (RVLT) Project. These models were developed using open data sources, assuming current and advanced technology levels, and range from 650 to 7,500 shaft output horsepower (485 to 5,600 kilowatts). Documenting the methodology, assumptions, and resulting performance realizes important benefits for NASA and the aviation community. NASA concept vehicle efforts using these propulsion models can more readily shared among the government, industry and university community as common baselines to support current and future work. Assessing the benefits of advanced technologies and new configurations can be facilitated using these models, which helps guide technology investment. As the various modeling conceptual vehicle and mission analysis environments advance, these models can be used directly for broader systems analysis studies, including optimization within the propulsion model itself. To perform this effort, the turboshaft engine is briefly discussed, highlighting the specific components and their expected performance characteristics over the power range and technology levels considered. Engine configurations will also be discussed as they will vary based on power output and assumed technology level. Engine performance, such as airflow, power output and weight will be reported, noting trends that are important for system studies. The effect of advanced propulsion technologies on RVLT-concept vehicles are also reported. Finally, potential future propulsion modeling work will be proposed.
    Keywords: Aircraft Propulsion and Power
    Type: VFS-Forum75-Paper-231 , GRC-E-DAA-TN68629 , Annual Vertical Flight Society (VFS 2019) Forum and Technology Display (Forum 75); May 13, 2019 - May 16, 2019; Philadelphia, PA; United States
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  • 13
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    PIV/Phased Array/Far-Field Noise Measurements of a Low-Noise Top-Mounted Propulsion Installation for a Supersonic Airliner (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A model-scale exhaust system was tested to validate low-noise concepts and noise prediction methods. The tests involved far-field acoustics, translating phased array, and particle image velocimetry; this report covers the far-field acoustic measurements. Data were acquired for a series of nozzles with different chevron designs, both uninstalled and installed on a representative aircraft planform. The impact of the various chevron treatments on the far-field noise was documented, along with the impact of the pylon and planform. For the baseline nozzle, installation produced a 2 EPNdB (Effective Perceived Noise in deciBels) reduction, as assumed in system studies. Chevrons were used to shift noise sources upstream to maximize the installation benefits and to reduce unshielded sources downstream. These resulted in reductions of 4-5 EPNdB...
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN67394 , Acoustics Technical Working Group (ATWG) Spring 2019 Meeting; Apr 10, 2019 - Apr 12, 2019; Hampton, VA; United States
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  • 14
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    Modeling Turboshaft Engines for the Revolutionary Vertical Lift Technology Project (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Turboshaft engine performance and weight models were developed to support conceptual propulsion and vehicle mission design and performance under the Revolutionary Vertical Lift Technology (RVLT) Project. These models were developed using open data sources, assuming current and advanced technology levels, and range from 650 to 7,500 shaft output horsepower (485 to 5,600 kW). Documenting the methodology, assumptions, and resulting performance realizes important benefits NASA and the aviation community. NASA concept vehicle efforts using these propulsion models can be more readily shared among the government, industry and university community as common baselines to support current and future work. Assessing the benefits of advanced technologies and new configurations can be facilitated using these models, which helps guide technology investment. As the various modeling conceptual vehicle and mission analysis environments advanced, these models can be used directly for broader systems analysis studies, including optimization within the propulsion model itself. To perform this effort, the turboshaft engine is briefly discussed, highlighting the specific components and their expected performance characteristics over the power range and technology levels considered. Engine configurations will also be discussed as they will vary based on power output and assumed technology level. Engine performance, such as airflow, power output and weight will be reported, noting trends that are important for system studies. The effect of advanced propulsion technologies on RVLT concept vehicles are also reported. Finally, potential future propulsion modeling work will be proposed.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN66991 , Annual Forum and Technology Display: The Future of Vertical Flight; May 13, 2019 - May 16, 2019; Philadelphia, PA; United States
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    NASA TECHNICAL REPORTS
  • 15
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    New Test Rig to Measure Alternating Current Losses of Both Low and High Critical Temperature Superconductors (2019)
    In:  CASI
    Details
    Publication Date: 2019-06-18
    Description: This paper presents the design, development, operation, and test capabilities of a proposed superconducting coil testbed to measure alternating current (AC) losses at the NASA Glenn Research Center. Superconducting AC losses are important in the design of electric stators and rotors, power transmission lines, transformers, fault current limiters, magnets, and superconducting energy storage (not batteries). The new liquid-hydrogen-based rig will allow superconducting testing across a wide range of test parameters, including injected current up to 400 A, frequency (0 to 400 Hz), magnetic field (0 to 0.6 T), phase angle between induced voltage and injected current (180 to 180), coil coolant temperature (18 to 28 K), and AC power loss (5 to 30 W). While the target application of interest is 20 K superconducting MgB2 (the only superconductor that can presently be made with low losses) stator coils for future electric machines, the rig can accommodate test articles (TAs) with straight wire, tape, cables, coils of any shape, any allowable combination of superconducting wire and fluid (e.g., yttrium barium copper oxide (YBCO) coils and liquid nitrogen), and AC or direct current (DC) testing. The new spin rig builds upon the existing Air Force spin rig through a more flexible mode of fluid control, a wider gap space (up to 10.2 cm) for TAs, and the ability to accommodate TAs over a wider range of operating temperatures (18 to 95 K) using liquid hydrogen, gaseous helium, or liquid nitrogen as the working fluid, thus supporting direct cooled machines below 77 K.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN63356 , NASA/TM-2019-220046 , E-19642-TN63356
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  • 16
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    Preliminary Computational Assessment of Disk Rotating Detonation Engine Configurations (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The pressure gain combustion (PGC) community is currently investigating rotating detonation engine (RDE) configurations where the flow direction is predominantly radial while the detonation travels circumferentially. These configurations are sometimes referred to as disk rotating detonation engines (DRDE) due to their nominal appearance as two disks in parallel with a gap between them. Having radial flow between disks, as opposed to the conventional RDE with axial flow in an annulus, may have profound effects on both the flow field and the performance. It may also yield extraordinarily compact devices which are well suited to particular propulsion and power applications. This presentation describes a preliminary effort to model the DRDE using a modified computational fluid dynamics (CFD) code originally written for analyzing ordinary RDE's. The quasi-two-dimensional code modifications are described, and some simple test flows are analyzed to insure that the modifications are functioning as envisioned. The code is then used to examine several DRDE scenarios such as radially inward and radially outward devices to see if stable operation is possible and if so, to assess the performance in terms of pressure gain. It is found that several flow scenarios are not only stable, but show superior performance to the ordinary RDE.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN68851 , Programmatic and Industrial Base (PIB); Jun 03, 2019 - Jun 07, 2019; Dayton, OH; United States|JANNAF Propulsion Meeting (JPM); Jun 03, 2019 - Jun 07, 2019; Dayton, OH; United States|Propulsion Systems Hazards Subcommittee (PSHS); Jun 03, 2019 - Jun 07, 2019; Dayton, OH; United States|Exhaust Plume and Signatures Subcommittee (EPSS); Jun 03, 2019 - Jun 07, 2019; Dayton, OH; United States|Combustion Subcommittee (CS); Jun 03, 2019 - Jun 07, 2019; Dayton, OH; United States|Airbreathing Propulsion Subcommittee (APS); Jun 03, 2019 - Jun 07, 2019; Dayton, OH; United States
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  • 17
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    Electric Aircraft Cryogenic Cooling with Thermo-Acoustic Exergy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-21
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN68513 , 2019 Cryogenic Engineering Conference and International Cryogenic Materials Conference; Jul 21, 2019 - Jul 25, 2019; Hartford, CT; United States
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  • 18
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    Electromagnetic Mass and Efficiency of Magnetic Gears for Electrified Aircraft (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-30
    Description: Magnetic gears are currently being developed for use in a variety of industries such as wind and automotive, because of their higher reliability and lower maintenance cost than their mechanical counterparts. The bulk of magnetic gear development to date has focused on maximizing the technology's volumetric torque density. In contrast, the primary performance metrics for an aircraft's gear box are its mass and efficiency. To that end this paper presents a study of the achievable electromagnetic specific torque and efficiency of concentric magnetic gears. NASA's second magnetic gear prototype is used as the baseline for this study. Achievable electromagnetic specific torque and efficiency trends are presented with respect to higher level design variables such as gear ratio and radius.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70582 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN
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    NASA TECHNICAL REPORTS
  • 19
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    Design of a Magnetic Gear for NASA's Vertical Lift Quadrotor Concept Vehicle (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-30
    Description: Magnetic gears are an attractive alternative to mechanical gears for electrified aircraft drive systems due to their ability to transmit torque without mechanical tooth contact. Consequently, magnetic gears enable electrified aircraft to take advantage of the benefits of gearing without introducing most of the contact-related reliability concerns associated with mechanical gearing. Magnetic gears however, have not been shown to match the specific torque (torque/mass) and efficiency of their mechanical counterparts in an aerospace application to date. In this paper, the design of a concentric magnetic gear for a personal air transport NASA reference vehicle is presented to demonstrate the feasibility of a magnetic gear for aerospace applications.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70579 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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    NASA TECHNICAL REPORTS
  • 20
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    Exit Boundary Layer Data for a Round Convergent Nozzle in Support of Numerical Simulation Efforts (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-30
    Description: An experiment is conducted with hot-wire anemometry to document the exit boundary layer characteristics of two nozzle configurations at jet Mach numbers up to 0.82. Far-field noise and jet plume experimental data from these two configurations have been used in Large Eddy Simulations (LES) of jets by colleagues at other Institutions. The current experiment provides the boundary layer data which have been identified as being critical for validation of the simulations since the initial conditions can significantly affect subsequent jet evolution and its radiated noise. The data exhibit fully turbulent boundary layers for the case with a pipe attached upstream of the nozzle. The case without the pipe involves Blasius-like mean velocity profiles but a highly disturbed laminar state with large turbulence intensities in a range of subsonic Mach numbers.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220242 , E-19719 , GRC-E-DAA-TN70914
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  • 21
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    Electrical Power System Sizing Within the Numerical Propulsion System Simulation (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Electrified aircraft propulsion seeks to address ambitious goals in the commercial airline industry, including significant decreases in fuel burn, emissions, noise, and takeoff field length. In order to move these electrified propulsion concepts forward, analysis tools are needed that can model propulsion systems containing both gas turbine and power system components. This work presents the definition of an electric port, a set of electrical power systems tools, and simulation examples for the Numerical Propulsion System Simulation (NPSS) software. NPSS is the industry standard modeling and simulation package for aircraft propulsion systems, and the ability to design, size, integrate, and analyze electric power systems will enable industry efforts towards the development of electrified aircraft propulsion.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70658 , AIAA Propulsion and Energy Forum and Exposition; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    NASA TECHNICAL REPORTS
  • 22
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    CFD Evaluation Of Lean-Direct Injection Combustors for Commercial Supersonics Technology (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-11
    Description: An overview is given of an effort that focused on using CFD analysis to complement design and configuration definition of Lean-Direct Injection (LDI) combustion concepts for NASA's Commercial Supersonic Transport (CST) program. The National Combustion Code (OpenNCC) was used to perform non-reacting and two-phase reacting flow computations for second and third generation LDI configurations at CST cruise conditions. All computations were performed with a consistent approach of mesh-generation, spray modeling, ignition and kinetics modeling. Emissions (EINOx) characteristics were predicted for CST cruise conditions, and compared with emissions data from experimental measurements to evaluate the fidelity of the CFD modeling approach to predict emissions changes in response to changes in supersonic cycle conditions.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72416 , AIAA Propulsion and Energy Forum; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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  • 23
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    High Efficiency Megawatt Machine Rotating Cryocooler Conceptual Design (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: Some of the challenges associated with developing electric aircraft propulsion systems include developing powertrain components that are both efficient and light-weight. In particular, electric motors must simultaneously achieve high efficiency by minimizing electrical and mechanical losses while also achieving high specific power by increasing the torque and/or speed. Normally increasing torque or speed will increase electrical and mechanical losses. The High Efficiency Megawatt Machine (HEMM) minimizes electrical losses by incorporating a superconductor to enable increased current on the rotor. And the rotor spins in a vacuum to minimize thermal and mechanical losses. Some organizations have been developing superconducting rotors for similar reasons using either cryogenic fluid transfer systems, fully immersed cryogenic cooling, and in a few cases utilized built-in cryogenic cooling on the rotor using a Brayton or Stirling system but the implementation was too large or inefficient for effective motor integration. Instead, a new approach for cryogenically cooling the superconducting rotor coil with an embedded rotating cryocooler is presented that fits completely within the rotating shaft.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN71027 , AIAA/IEEE Electric Aircraft Technologies Symposium; Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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  • 24
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    Computational Modeling for Non-equilibrium Shock Tube Flows (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-07
    Description: Time accurate simulation of non-equilibrium flows inside shock tube facilities presents several challenges from both physical and mathematical aspects. Furthermore, the drastic computational cost makes it non-practical to support real-time experimental test campaign. In this work, we explore other methods for modeling the shock tube prob- lem with the main focus on the post-shock region and the absolute radiation emanating from it. The proposed alternative approach is several orders of magnitude less computa- tionally expansive while still accurate enough with regards to the quantities of interest. Excellent agreement is found with the well-established stagnation-line approach. Comparison with the time-accurate simulation shows good agreement close to the peak values and disagreement of the temperatures relaxation and radiance profiles toward equilibrium, due to shock speed unsteadiness.
    Keywords: Aircraft Propulsion and Power
    Type: ARC-E-DAA-TN70486 , International Symposium on Shock Waves (ISSW32); Jul 14, 2019 - Jul 19, 2019; Singapore; China
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    X-57 60kW Permanent Magnet Synchronous Cruise Motor Finite Element Electromagnetic Modeling (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-28
    Description: The X-57 60kW Permanent Magnet Synchronous Motor for cruise applications was modeled utilizing a two-dimensional electromagnetics simulation software called Finite Element Method Magnets (FEMM, D. Meeker). Through FEMM, the simulated induction and torque characteristics of the X-57 PMSM were obtained. These parameters and other values were compared to actual static laboratory measurements. A three-dimensional electromagnetic model of the X-57 cruise motor was created utilizing OperaFEA (Dassault Systemes SE, Velizy-Villacoublay, France). Torque, RPM, power, resistance, and inductance characteristics were examined along with establishing work to begin examining heat flow and heat dissipation for efficiency purposes.
    Keywords: Aircraft Propulsion and Power
    Type: AFRC-E-DAA-TN75616 , Southern California Conferences for Undergraduate Research (SCCUR); Nov 23, 2019; San Marcos, CA; United States
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    Design of Low Inductance Busbar for 500 kVA Three-Level ANPC Converter (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-08
    Description: The adoption of SiC devices in high power applications enables higher switching speed, which requires lower circuit parasitic inductance to reduce the voltage overshoot. This paper presents the design of a busbar for a 500 kVA three-level active natural clamped converter. The layout of the busbar is discussed in detail based on the analysis of the multiple commutation loops, magnetic cancelling effect, and DC-link capacitor placement. The loop inductance of the designed busbar is verified with simulation, impedance measurements and converter experiment. The results can match with each other and the inductances of small and large loop are 6.5 nH and 17.5 nH respectively, which is significantly lower than the busbars of NPC type converters in other references.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN68912 , 2019 IEEE Energy Conversion Congress and Exposition; Sep 29, 2019 - Oct 03, 2019; Baltimore, MD; United States
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    Electrical Propulsive Fuselage Concept for Transonic Transport Aircraft (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-08
    Description: NASA is broadly engaged in Electrified Aircraft Propulsion (EAP) efforts across air vehicle sizes and electric aircraft propulsion approaches. EAP enables a wide range of propulsion airframe integration options as well as the use of rechargeable energy storage in an aircraft. This paper is limited to a discussion of boundary layer ingestion (BLI) systems which are located on the fuselage of the aircraft and use electrical drive systems. We term that combination an "electrical propulsive fuselage". The benefits, challenges, and design parameters of an electrically driven fuselage BLI system are considered. Five existing types of fuselage BLI implementation approaches which can be implemented using either electrical or mechanical drive systems are reviewed. An overview of boundary layer types, fan response to boundary layer, and electrical system for aircraft propulsion is presented. An idea distributed electric propulsive fuselage is proposed.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72037 , International Society for Air Breathing Engines (ISABE) 2019; Sep 22, 2019 - Sep 27, 2019; Canberra; Australia
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    Pilot Injector Redesign to Reduce N+3 Cycle Emissions for a Gas-Turbine Combustor (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-11
    Description: An overview is given of an effort for the use of CFD analysis to complement design and configuration definition of third generation Lean-Direct Injection combustion concepts (LDI-3) for NASAs N+3 program. The National Combustion Code (OpenNCC) was used to perform non-reacting and two-phase reacting flow computations for a three-cup, nineteen-element flame tube array with redesigned pilot injectors to improve spray and emissions characteristics when compared to a previous LDI-3 design. All computations were performed with a consistent approach to mesh-generation, spray modeling, ignition and kinetics modeling for a medium-power cycle condition. Computational predictions of the aerodynamics of a new pre-filming pilot injector were used to arrive at an optimized aerothermal design that meets effective area and fuel-air mixing criteria. The newly designed pilot injectors were shown to provide considerable improvements in aerodynamic stability, flame-tube pattern factor and NOx emissions, when compared to the original design.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70810 , AIAA Propulsion and Energy Forum; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    Electromagnetic Efficiency and Mass of Magnetic Gears for Electrified Aircraft (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: Magnetic gears are currently being explored to replace mechanical gears in various industries such as wind and automotive due to their higher reliability and lower maintenance requirements. In these applications volume minimization has been the goal of magnetic gear development. In contrast, the primary performance metrics for electrified aircraft drives are mass and efficiency. This paper presents the first ever study of design tradeoffs between electromagnetic mass and efficiency of concentric magnetic gears and the feasibility of achieving the low mass and high efficiency required for electrified aircraft applications. Higher level design variables are considered, including gear ratio, number of magnetic pole pairs, and number of magnets per pole pair.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72224 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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    Defining and Measuring Pressure Gain (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: This presentation describes experimental and computational approaches to measuring pressure gain in the various devices currently under investigation wherein the working fluid undergoes a pressure gain combustion (PGC) process. Pressure gain is essentially a measure of the fluid availability for work or thrust production. The devices covered are Resonant Pulse Combustors, Internal Combustion Wave Rotors, Pulse Detonation Engines, and Rotating Detonation Engines. The approaches to pressure gain measurement differ in each device. However, all of the approaches attempt to address the fundamental challenges of PGC system measurement: the extremely harsh environment which makes instrumentation difficult, and the temporal and spatial non-uniformity associated with the exhausting flow which makes assigning a single value to the total pressure difficult. As part of the two-day 2019 International Constant Volume and Detonative Combustion Workshop, held in conjunction with the 2019 AIAA Propulsion and Energy Forum, this presentation is intended to foster discussion and eventual consensus on acceptable measurement methods.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN71983 , International Constant Volume Detonation Combustion Workshop; Aug 17, 2019 - Aug 18, 2019; West Lafayette, IN; United States
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    Fuel Sensitivity of Lean Blowout in a RQL Gas Turbine Combustor (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-06
    Description: Transition from fossil fuels to synthetic drop-in fuels without the need to change existing combustors is the current research topic. The combustor performances such as cold-day ignition limits, lean blow-out (LBO) limits and altitude relight limits are the main focus points. The objective of this work is to evaluate the effect of different fuel candidates on the operability of gas turbines by comparing a conventional petroleum-based fuel with one other alternative fuel candidate. Time filtered Navier-Stokes simulations (TFNS) and K-LES are performed to examine the performance of these fuels at the stable conditions close to blow-out in a referee combustor rig.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70667 , AIAA Propulsion and Energy Forum 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    Combustion and Emissions Study Using a 7-Point Lean Direct Injector Array (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-02
    Description: This paper continues a parametric study in which we consider the effect of air swirler configuration on the flame structure and combustor performance using a circular 7-point Lean Direct Injector Array for gas turbine applications. The injector array consists of a center swirler element surrounded by six swirler elements. Parameters considered in this study include swirler angle (60 or 52), handedness (co-swirling or counter-swirling) and center swirler offset. The primary focus considers flame stability, comparing four key air swirler configurations: for 1) fuel-lean flames; 2) high cold flow air reference velocity flames. We determined that the baseline swirler configuration had the best lean stability and could sustain the highest reference velocity. For this baseline configuration, we also compare the lean-blowout limits of four aircraft gas turbine reference fuels. With regard to lean blow-out, we determined that C4 could sustain the leanest flame, followed closely by A2. A1 was a poor performer.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70824 , ISABE-2019-24404 , The International Society for Air Breathing Engines (ISABE) 2019 Conference; Sep 22, 2019 - Sep 27, 2019; Canberra; Australia
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    Results of NASA's Magnetic Gear Program to Date (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-26
    Description: In rotorcraft, one of the main sources of mechanical failure is the gearbox, because of the many wear and failure modes associated with tooth contact in traditional mechanical gear boxes. Magnetic gears transmit torque without mechanical tooth contact between gear bodies and therefore they have none of the tooth contact related failure modes associated with mechanical gearing. As a result, magnetic gears have the potential to enable more reliable rotorcraft gearboxes. However, magnetic gears have not been demonstrated to match the performance of mechanical gearboxes at a high enough technology readiness level (TRL) to be used on an aircraft to date. To that end, NASA's Revolutionary Vertical Lift Technologies project has made an investment in developing magnetic gearboxes specifically for electrified vertical lift vehicles (EVTOL). In this presentation, the results of that investment to date will be discussed.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN73679 , Vertical Flight Society (VFS) Propulsion and Power Technical Meeting; Oct 29, 2019 - Oct 30, 2019; Hampton, VA; United States
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    NASA Investments in Electrified Propulsion (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-18
    Description: Presentation to the International Forum on Aviation (IFAR) at the Electric Hybrid Propulsion Workshop #2 in Budapest, Hungary. This presentation is to provide an overview of NASA's investments in electrified propulsion as a starting point for the workshop, which will concentrate on the safety of electrified airplanes and potential for international collaboration.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN74945
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    NASA Electrified Propulsion Research Summary (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-09
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN74525 , HQ-E-DAA-TN72474 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States|Energy Tech; Oct 22, 2019 - Oct 24, 2019; Cleveland, OH; United States
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    Applying Optical Diagnostics to Study Aircraft Gas Turbine Combustor Performance (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-03
    Description: This is for an invited lecture at Cleveland State University for a combustion course. The presentation gives an overview of some of the optical diagnostic techniques the Combustion Branch uses to characterize research fuel injection concepts to reduce emissions. Examples are provided that come from previously presented conference papers
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN74916
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    Effective Oxidation Model for Light-Weight Carbon Preform Ablators (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-16
    Description: Porous Microstructure Analysis (PuMA) software is used to perform simulations of molecular beam scattering experiments of hyperthermal atomic oxygen striking FiberFormr, a carbon preform material used commonly as a precursor in thermal protection systems (TPS). The purpose of this study is to investigate the reactive interaction of fibrous carbon with atomic oxygen in a complex microstructure, which is the primary source of carbon removal at lower temperatures. The detailed micro-structure of FiberFormr obtained from X-ray micro-tomography is used in the PuMA simulations to capture the complexity of the porous and fibrous characteristic of FiberFormr. A finite-rate surface chemistry model recently constructed from the molecular beam scattering experiments on vitreous carbon is applied to each fiber of the FiberFormr material. This model consists of detailed surface reaction mechanisms such as adsorption, desorption, and several types of Langmuir-Hinshelwood (LH) reactions to characterize the oxygen-carbon interactions at the surface. Comparison between the experimental and PuMA time-of-flight (TOF) distributions of both O and CO show good agreement. It is also found that a significantly higher amount of CO is generated when the beam interacted with FiberFormr, when compared with vitreous carbon. This is postulated to be primarily a result of multiple collisions of oxygen with the fibers, resulting in an higher effective rate of CO production. Multiple collisions with the different fibers, resulting from the porous nature of FiberFormr is also found to thermalize the O atoms, in addition to the adsorption/desorption process. The effect of micro-structure is concluded to be crucial in determining the final composition and energy distributions of the products. Thus, an effective model for the oxygen interaction with FiberFormr, fully accounting for the detailed micro-structure, for use in Computational Fluid Dynamics (CFD) and material response codes, is presented.
    Keywords: Aircraft Propulsion and Power
    Type: ARC-E-DAA-TN64596 , AIAA SciTech Forum 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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    Feasibility of Electrified Propulsion for Ultra-Efficient Commercial Aircraft Final Report (2019)
    In:  CASI
    Details
    Publication Date: 2019-12-18
    Description: MIT, Aurora Flight Sciences, and USC have collaborated to assess the feasibility of electric, hybridelectric, and turbo-electric propulsion for ultra-efficient commercial transportation. The work has drawn on the team expertise in disciplines related to aircraft design, propulsion-airframe integration, electric machines and systems, engineering system design, and optimization. A parametric trade space analysis has been carried out to assess vehicle performance across a range of transport missions and propulsion architectures to establish how electrified propulsion systems scale. An optimization approach to vehicle conceptual design modeling was taken to enable rapid multidisciplinary design space exploration and sensitivity analysis. The results of the analysis indicate vehicle aero-propulsive integration benefits enabled by electrification are required to offset the increased weight and loss associated with the electric system and achieve enhanced performance; the report describes the conceptual configurations than can offer such enhancements. The main contribution of the present work is the definition of electric vehicle design attributes for potential efficiency improvements at different scales. Based on these results, key areas for future research are identified, and extensions to the trade space analysis suitable for higher fidelity electrified commercial aircraft design and analysis have been developed.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72076 , NASA/CR—2019-220382
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    A Control Strategy for Turbine Electrified Energy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-07
    Description: Hybrid electric propulsion architectures provide the infrastructure to enable additional benefits to the propulsion system that are otherwise unrealizable with the sole use of the current, state-of-the-art, gas-driven, turbine engines. The presence of electric machines (EMs) coupled to the shaft(s) of the turbine engine provide the ability to actively alter the operation of the engine to the benefit of the propulsion system and the aircraft it propels. This is the goal of the Turbine Electrified Energy Management (TEEM) concept, which at its broadest level addresses the management of energy across the electrified propulsion system. Prior work has demonstrated the use of this concept to alter steady-state operation and improve transient operability of a hybrid-electric propulsion system. The main benefits previously illustrated include the elimination of stability bleeds and expansion of the turbomachinery design space in order to enable more efficient designs. This paper focuses on the development of control strategies to implement the TEEM concept, and it explores several possible architecture variants for applying this concept. Comparison studies are conducted between a purely gas-driven turbofan (baseline engine configuration) and TEEM augmented variants of the baseline engine. The variants are distinguished by the shaft(s) that possess an EM. The configurations consider EMs on both shafts, an EM on the high pressure spool (HPS) only, and an EM on the low pressure spool (LPS) only. These configurations are referred to as the dual-spool configuration, the HPS configuration, and LPS configuration, respectively. The studies expose several options in configuring and controlling the system, including the use of a single EM coupled to a single shaft of a two-spool engine to positively impact the operability of both shafts. The studies also demonstrate the use of independently designed controllers for the electric machine(s) that allow for a decoupled control design process.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70128 , AIAA/IEEE Electric Aircraft Technology Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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    NASA Electrified Aircraft Propulsion Efforts (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-14
    Description: NASA's broad investments in Electrified Aircraft Propulsion (EAP) are reviewed in this paper. NASA investments are guided by an assessment of potential market impacts, technical key performance parameters, and technology readiness attained through a combination of studies, enabling fundamental research, and flight research. NASA has determined that the impact of EAP varies by market and NASA is considering three markets: national/international, on-demand mobility, and short haul regional air transport. Flight research is underway to demonstrate integrated solutions and inform standards and certification processes. This paper focuses on the vehicle related activities, however there are related NASA activities in air space management and vehicle autonomy activities as well as a breakthrough technology project called the Convergent Aeronautics Solutions Project. A key finding is that sufficient technical advances in key areas have been made which indicate EAP is a viable technology for aircraft. Significant progress has been made to reduce EAP adoption barriers and further work is needed to transition the technology to a commercial product and improve the technology so it is applicable to large transonic aircraft. This paper will review the activities of the Hybrid Gas Electric Subproject of the Advanced Air Transport Technology Project, the Revolutionary Vertical Lift Technology Project, and the X-57 Flight Demonstration Project, and discuss the potential EAP benefits for commercial and military applications.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72947 , Hybrid/Electric Aero-Propulsion Systems for Military Applications; Oct 07, 2019 - Oct 09, 2019; Trondheim; Norway
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    CFD Evaluation of Lean-Direct Injection Combustors for Commercial Supersonics Technology (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: An overview is given of an effort that focused on using CFD analysis to complement design and configuration definition of Lean-Direct Injection (LDI) combustion concepts for NASA's Commercial Supersonic Transport (CST) program. The National Combustion Code (OpenNCC) was used to perform non-reacting and two-phase reacting flow computations for second and third generation LDI configurations at CST cruise conditions. All computations were performed with a consistent approach of mesh-generation, spray modeling, ignition and kinetics modeling. Emissions (EINOx) characteristics were predicted for CST cruise conditions, and compared with emissions data from experimental measurements to evaluate the fidelity of the CFD modeling approach to predict emissions changes in response to changes in supersonic cycle conditions.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70736 , AIAA Propulsion and Energy Forum 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    High Efficiency Megawatt Machine Rotating Cryocooler Conceptual Design (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Some of the challenges associated with developing electric aircraft propulsion systems include developing powertrain components that are both efficient and light-weight. In particular, electric motors must simultaneously achieve high efficiency by minimizing electrical and mechanical losses while also achieving high specific power by increasing the torque and/or speed. Normally increasing torque or speed will increase electrical and mechanical losses. The High Efficiency Megawatt Machine (HEMM) minimizes electrical losses by incorporating a superconductor to enable increased current on the rotor. And the rotor spins in a vacuum to minimize thermal and mechanical losses. Some organizations have been developing superconducting rotors for similar reasons using either cryogenic fluid transfer systems, fully immersed cryogenic cooling, and in a few cases utilized built-in cryogenic cooling on the rotor using a Brayton or Stirling system but the implementation was too large or inefficient for effective motor integration. Instead, a new approach for cryogenically cooling the superconducting rotor coil with an embedded rotating cryocooler is presented that fits completely within the rotating shaft.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70902 , AIAA/IEEE Electric Aircraft Technologies Symposium; Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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    Exit Boundary Layer Data for a Round Convergent Nozzle in Support of Numerical Simulation Efforts (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-08-22
    Description: An experiment is conducted with hot-wire anemometry to document the exit boundary layer characteristics of two nozzle configurations at jet Mach numbers up to 0.82. Far-field noise and jet plume experimental data from these two configurations have been used in Large Eddy Simulations (LES) of jets by colleagues at other Institutions. The current experiment provides the boundary layer data which have been identified as being critical for validation of the simulations since the initial conditions can significantly affect subsequent jet evolution and its radiated noise. The data exhibit fully turbulent boundary layers for the case with a pipe attached upstream of the nozzle. The case without the pipe involves Blasius-like mean velocity profiles but a highly disturbed laminar state with large turbulence intensities in a range of subsonic Mach numbers.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220242/SUPP , E-19719 , GRC-E-DAA-TN70914
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    Control Technology Needs for Electrified Aircraft Propulsion Systems (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Electrified aircraft propulsion (EAP) systems hold potential for the reduction of aircraft fuel burn, emissions, and noise. Currently, NASA and other organizations are actively working to identify and mature technologies necessary to bring EAP designs to reality. This paper specifically focuses on the envisioned control technology challenges associated with EAP designs that include gas turbine technology. Topics discussed include analytical tools for the dynamic modeling and analysis of EAP systems, and control design strategies at the propulsion and component levels. This includes integrated supervisory control facilitating the coordinated operation of turbine and electrical components, control strategies that seek to minimize fuel consumption and lessen the challenges associated with thermal management, and dynamic control to ensure engine operability during system transients. These dynamic control strategies include innovative control approaches that either extract or supply power to engine shafts dependent upon operating phase, which may improve performance and reduced gas turbine engine weight. Finally, a discussion of control architecture design considerations to help alleviate the propulsion/aircraft integration and certification challenges associated with EAP systems is provided.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN69695 , ASME Turbo Expo 2019; Jun 17, 2019 - Jun 21, 2019; Phoenix, AZ; United States
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    Control Technology Needs for Electrified Aircraft Propulsion Systems (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Electrified aircraft propulsion (EAP) systems hold potential for the reduction of aircraft fuel burn, emissions, and noise. Currently, NASA and other organizations are actively working to identify and mature technologies necessary to bring EAP designs to reality. This paper specifically focuses on the envisioned control technology challenges associated with EAP designs that include gas turbine technology. Topics discussed include analytical tools for the dynamic modeling and analysis of EAP systems, and control design strategies at the propulsion and component levels. This includes integrated supervisory control facilitating the coordinated operation of turbine and electrical components, control strategies that seek to minimize fuel consumption and lessen the challenges associated with thermal management, and dynamic control to ensure engine operability during system transients. These dynamic control strategies include innovative control approaches that either extract or supply power to engine shafts dependent upon operating phase, which may improve performance and reduced gas turbine engine weight. Finally, a discussion of control architecture design considerations to help alleviate the propulsion/aircraft integration and certification challenges associated with EAP systems is provided.
    Keywords: Aircraft Propulsion and Power
    Type: GT2019-91413 , GRC-E-DAA-TN65573 , ASME Turbomachinery Technical Conference & Exposition; Jun 17, 2019 - Jun 21, 2019; Phoenix, AZ; United States
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    A New Recycling Method to Generate Turbulent Inflow Profiles (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The accuracy of the scale-resolving simulations for practical geometries strongly depends on the inflow boundary conditions. Imposing experimentally observed turbulent inflow profiles for the numerical simulations is a major challenge. Existing methods available in the literature assume self-similar behavior, which is not true for most of the experiments. In the present work, we formulate the turbulent inflow profile generation technique as an optimization problem. An adjoint technique is exploited to evaluate the sensitivities of multiple input parameters for the present problem. The present formulation is then tested to generate a laminar boundary layer profile, turbulent boundary layer profile, and turbulent jet profile.
    Keywords: Aircraft Propulsion and Power
    Type: ARC-E-DAA-TN69970 , AIAA Aviation 2019; Jun 17, 2019 - Jun 21, 2019; Dallas, TX; United States
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    Lessons Learned in Fabrication of a High-Specific-Torque Concentric Magnetic Gear (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Magnetic gearing is being investigated at NASA as a replacement to conventional mechanical gearing in aerospace applications. Some key benefits of magnetic gears over mechanical gearing are torque transmission without mechanical contact, decreased transmission noise, less frequent maintenance, and lack of lubrication. In order to take advantage of these benefits in aerospace applications, magnetic gearing must be shown to provide high enough specific torque (torque per unit mass). Prototype 2 (PT-2), developed to maximize specific torque, and fabricated at NASA Glenn Research Center, has shown promising specific torque comparable to low torque mechanical gears. This work will briefly review the electromagnetic and structural design of PT-2, provide detailed information on fabrication and assembly, examine build errors, walk through rebuild efforts to improve operation, and conclude with remarks on build difficulties and opportunities for improvement in future prototypes.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN67458 , Vertical Flight Society Annual Forum and Technology Display; May 13, 2019 - May 16, 2019; Philadelphia, PA; United States
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    The Effect of Incoming Boundary Layer Characteristics on the Performance of a Distributed Propulsion System (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental study is conducted in an effort to advance the understanding of flow physics associated with a boundary layer ingesting, distributed propulsion system. The influence of incoming boundary layer thickness and flow distortions are studied on the flow downstream and the overall performance of the system. The propulsion model, fabricated using additive manufacturing and integrated with electrical fans, is mounted on a flat plate and tested at subsonic speeds. Detailed characterization of the incoming boundary layer and subsequent assessment of the downstream flow field is performed using hotwire anemometry. Modification of the incoming boundary layer is achieved by placing tripping devices, such as rods and vortex generating ramps, near the leading edge of the flat plate. The overall performance of the system for different incoming flow conditions is analyzed by comparing magnitudes of exhaust velocities as well as estimated propulsive power to the corresponding baseline values. For a constant input power to the fans, smaller upstream flow distortions and moderately thickened boundary layers result in marginal changes in the flow field downstream. On the other hand, notable reductions in downstream flow velocities and propulsive power are observed in the case of a significantly thicker and/or distorted incoming boundary layer. It is hoped that this study will serve as a database for this technologically relevant flow field that has not been explored adequately before.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM—2019-220068 , E-19658 , GRC-E-DAA-TN65193 , 2019 Science and Technology Forum (SciTech); Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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    Operational Stability Limits in Rotating Detonation Engine Numerical Simulations (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An instability is described which arises in computational fluid dynamic (CFD) simulations of semi-idealized rotating detonation engines (RDE) configured with a throat at the exit. Its existence is verified by examining output from two independently developed CFD codes simulating the same configuration and producing solutions that agree well. The instability is shown to be thermo-acoustic in that a spatial integral of the product of pressure and heat release fluctuations develops a regular oscillation which grows in time. The instability can become severe enough to cause detonation failure. Its onset is shown to be closely linked to the size of the exit throat and the size of the inlet restriction; both parameters that strongly influence RDE performance. It is shown that the instability places a cap on ideal RDEperformance, but that an optimized exhaust throat and inlet restriction combination still yields substantial pressure gain. Other parametric sensitivities are also examined in terms ofinstability growth. These include axial length, inlet manifold pressure, and air-fuel ratio.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN63619 , AIAA SciTech Forum 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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  • 50
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    Experimental Investigation of a One-Sided Ejector Nozzle (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A fundamental exploratory experiment is conducted assessing the performance of a one-sided ejector with the eventual goal of noise reduction for jet engines. The hardware is comprised of an 8:1 rectangular nozzle together with an ejector box whose lower surface is flush with the lower lip of the nozzle. Secondary flow is allowed through a gap between the upper lip of the nozzle and a flap that constitutes the upper surface of the ejector. Wall static pressures and Pitot probe surveys are conducted to evaluate the performance of the ejector with variation of geometric parameters. It is found that addition of vortex generating tabs at the upper lip of the nozzle significantly increases secondary flow entrainment. The entrainment is further enhanced by a divergence of the ejector up-per surface. Limited noise measurements are done. The baseline ejector (without tabs) often encounters flow resonance with accompanying tones. The tabs have the additional benefit of eliminating those tones in all cases. However, for the tabbed case, addition of the ejector produces insignificant further noise reduction. This is due to the fact that the flow remains unmixed on the lower half of the ejector. The focus of ongoing and future efforts is to achieve sufficient mixing of the flow so that the exhaust velocities are uniformly low, while keeping the ejector hardware short and light-weight.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN62981 , SciTech 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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    Multi-Point Design and Optimization of a Turboshaft Engine for a Tiltwing Turboelectric VTOL Air Taxi (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes the design of a turboshaft engine for a tiltwing air taxi application. In this case, the tiltwing air taxi is intended to fly a 400-nautical mile mission with up to fifteen passengers. Engine requirements for the concept engine are taken from aircraft system studies where thrust is produced by four propellers driven by electric motors and powered by a single gas turbine engine. The purpose of this paper is to perform a cycle design optimization that minimizes fuel consumption and weight while respecting current technology limitations to meet mission requirements. To achieve results, the engine overall pressure ratio and maximum temperature at the exit of the combustor are set as the design parameters. Several sensitivity studies are also performed to visualize optimization trends. Results of the optimization study show solutions are heavily dependent on engine cooling flow requirements and exact mission requirements. This engine is intended for use in large system optimization research.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN62826 , AIAA SciTech Forum 2019; Jan 07, 2019 - Jan 11, 2019; San Diego, CA; United States
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    Evaluation of Electrical System Requirements for Implementing Turbine Electrified Energy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-05
    Description: Turbine Electrified Energy Management (TEEM) is a concept concerned with the management of energy in an electrified propulsion system. The management of energy in the hybrid-electric architecture has potential to benefit the turbomachinery and the aircraft it powers. The concept is particularly useful for improving operability during transient operation and could be leveraged to design a better performing engine. The concept utilizes electric machines coupled to the engine shafts and an electric power distribution system that includes energy storage. A controller is used to decide when and how energy is moved around the electrified propulsion system, particularly when considering energy conversion between mechanical and electrical forms. Prior work has shown that the electric machines can be used to supply/or extract supplemental power to/from the engine shafts to improve their operability and achieve or enable propulsion efficiency and performance benefits. However, the previous studies did not consider the practical constraints of the electrical machines and energy storage devices that are required for implementing the TEEM system architecture concept. This paper presents an integrated engine and electrical system model that is used to evaluate the electrical system requirements. The model captures the physics of the conceptual, Advanced Geared Turbofan 30,000lbf (AGTF30) engine, which features advanced technologies such as a compact gas turbine and a variable area fan nozzle. For this work, the engine is augmented with electrical system components that allow for the implementation of the TEEM concept. The evaluation presented suggests the potential of the TEEM concept to provide performance benefits for a turbofan engine.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70911 , AIAA/IEEE Electric Aircraft Technology Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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  • 53
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    Pilot Injector Redesign to Reduce N+3 Cycle Emissions for a Gas-Turbine Combustor (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-13
    Description: An overview is given of an effort for the use of CFD analysis to complement design and configuration definition of third generation Lean-Direct Injection combustion concepts (LDI-3) for NASA's N plus 3 program. The National Combustion Code (OpenNCC) was used to perform non-reacting and two-phase reacting flow computations for a three-cup, nineteen-element flametube array with redesigned pilot injectors to improve spray and emissions characteristics when compared to a previous LDI-3 design. All computations were performed with a consistent approach to mesh-generation, spray modeling, ignition and kinetics modeling for a "medium-power" cycle condition. Computational predictions of the aerodynamics of a new pre-filming pilot injector were used to arrive at an optimized aerothermal design that meets effective area and fuel-air mixing criteria. The newly designed pilot injectors were shown to provide considerable improvements in aerodynamic stability, flame-tube pattern factor and NOx emissions, when compared to the original design.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA 2019-4371 , GRC-E-DAA-TN72414 , AIAA/SAE/ASEE Joint Propulsion and Energy Forum and Exposition 2019 ; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    Design of a Magnetic Gear for NASA's Vertical Lift Quadrotor Reference Vehicle (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-11
    Description: Magnetic gears are an attractive alternative to mechanical gears for electrified aircraft drive systems due to their ability to transmit torque without mechanical tooth contact. Consequently, magnetic gears enable electrified aircraft to take advantage of the benefits of gearing without introducing most of the contact-related reliability concerns associated with mechanical gearing. Magnetic gears however, have not been shown to match the specific torque (torque/mass) and efficiency of their mechanical counterparts in an aerospace application to date. In this paper, the design of a concentric magnetic gear for a personal air transport NASA reference vehicle is presented to demonstrate the feasibility of a magnetic gear for aerospace applications.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72227 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS 2019); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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  • 55
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    Fuel Sensitivity of Lean Blowout in a RQL Gas Turbine Combustor (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-17
    Description: Transition from fossil fuels to synthetic drop-in fuels without the need to change existing combustors is the current research topic. The combustor performances such as cold-day ignition limits, lean blow-out (LBO) limits and altitude relight limits are the main focus points. The objective of this work is to evaluate the effect of different fuel candidates on the operability of gas turbines by comparing a conventional petroleum-based fuel with one other alternative fuel candidate. Time filtered Navier-Stokes simulations (TFNS) and K-LES are performed to examine the performance of these fuels at the stable conditions close to blow-out in a referee combustor rig.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72312 , AIAA Propulsion and Energy Forum 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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  • 56
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    An Analysis of the Strayton Engine, a Brayton and Stirling Cycle Recuperating Engine (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: This paper explores the novel Strayton engine concept. This engine combines the cycles of a Brayton engine with that of a Stirling engine to create a highly efficient recuperating gas turbine engine. In the explored case, both Brayton cycle and Stirling cycle engines are used to generate electrical power. Additionally, the Stirling engine is used to draw heat out of the Brayton turbine (acting to cool the turbine blades), while also pumping heat into Brayton cycle just before combustion occurs (acting as the mechanism for recuperation). The purpose of this paper is to detail the system level modeling techniques used to generate the simulation, perform a cycle analysis of the combined cycle engine, identify key technologies and challenges associated with the concept, and compare potential performance gains with existing gas turbine engines and internal combustion engines. Topics such as controls, blade cooling effects, engine weight, and heat transfer using heat pipe are also explored. Results from this work show potential architectures that could provide the required heat transfer rates, potential control strategies, and performance benefits, including efficiency gains between 10% and 3% on engines ranging from 200HP to 670HP with the combined cycle engine.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN71720 , AIAA Propulsion and Energy Forum 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    Dynamic Analysis of the STARC-ABL Propulsion System (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: In the pursuit of Electrified Aircraft Propulsion (EAP), much of the attention is on the development of hybrid electric concept vehicles and their propulsion systems from a steady state performance perspective. While it is steady-state performance that largely determines the efficiency of civil air transports, engine operability and transient performance define constraints for the steady state design that impact efficiency and system viability. Neglecting dynamics and control technologies can result in an over-designed, sub optimal propulsion system or a concept that is not feasible. Thus, dynamic system studies were conducted on the propulsion system of the conceptual aircraft design known as the Single-aisle Turboelectric AiRCraft with Aft Boundary Layer propulsor (STARC-ABL). This paper describes the development of a controller to verify the baseline concept's feasibility from an operability perspective. Further, studies were conducted to identify excessive stability margin in the baseline design that could be traded for potential benefits in efficiency through an engine re design. This study revealed the potential to reduce the high pressure compressor (HPC) stall margin by 3%. Finally, a study was conducted to investigate the potential benefit of adding energy storage to the STARC-ABL concept that further improves operability and enables more gains in engine efficiency and performance. The energy storage provided an additional 0.5% stall margin can be removed from the HPC.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70106 , AIAA Propulsion and Energy Forum; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    Control Technology Needs for Electrified Aircraft Propulsion Systems (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-04
    Description: Electrified aircraft propulsion (EAP) systems hold potential for the reduction of aircraft fuel burn, emissions, and noise. Currently, NASA and other organizations are actively working to identify and mature technologies necessary to bring EAP designs to reality. This paper specifically focuses on the envisioned control technology challenges associated with EAP designs that include gas turbine technology. Topics discussed include analytical tools for the dynamic modeling and analysis of EAP systems, and control design strategies at the propulsion and component levels. This includes integrated supervisory control facilitating the coordinated operation of turbine and electrical components, control strategies that seek to minimize fuel consumption and lessen the challenges associated with thermal management, and dynamic control to ensure engine operability during system transients. These dynamic control strategies include innovative control approaches that either extract or supply power to engine shafts dependent upon operating phase, which may improve performance and reduced gas turbine engine weight. Finally, a discussion of control architecture design considerations to help alleviate the propulsion/aircraft integration and certification challenges associated with EAP systems is provided.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220296 , GRC-E-DAA-TN70505 , E-19721 , ASME Turbomachinery Technical Conference & Exposition; Jun 17, 2019 - Jun 21, 2019; Phoenix, AZ; United States
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    Reliability Requirements and Research Strategies for Urban Air Mobility Propulsion (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-21
    Description: An emerging new mission for aeronautics is Urban Air Mobility (UAM), a concept for air transportation around metropolitan areas with passenger-carrying operations. UAM vehicles must be capable of vertical take-off and landing, and this requirement presents unique technical challenges for electric and hybrid-based vertical take-off and landing (eVTOL). A critical challenge for UAM market growth is to gain public acceptance for being as safe as - or safer than - commercial air travel and automotive transportation. There is a lack of data for propulsion systems, components, and the associated thermal management systems for UAM eVTOL propulsion systems. The new mission, new propulsion system concepts, safety criticality of propulsion component performance during vertical take-off and lift operations, and lack of data presents many research challenges and opportunities. NASA has developed and published UAM vehicle concept studies. For a subset of the said concept vehicles, NASA has contracted for a study to identify failure modes and hazards associated with the propulsion systems of the concept vehicles and to perform functional hazard analyses (FHA) and failure modes and effects criticality analyses (FMECA) for each. From the completed study results, it was recommended for NASA to support research toward developing electric/hybrid-electric propulsion components with improved reliability and to explore powertrain architectures that can take advantage of higher reliability components to achieve inherent air-vehicle safety. NASA has started a research effort for UAM propulsion with a focus toward improving safety and reliability. Recent results and research strategy will be discussed toward the goals by means of: 1) improving individual component reliability through advanced materials and design methods, 2) improving the thermal management system, and 3) designing propulsion system architectures to provide inherent UAM vehicle safety.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN74347 , 2019 Propulsion and Power Technical Meeting; Oct 29, 2019 - Oct 30, 2019; Hampton, VA; United States
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    Near-Exit Pressure Fluctuations in Jets from Circular and Rectangular Nozzles (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-15
    Description: This article documents some experimental observations made for near-exit unsteady pressure fluctuations in high-speed jets. These fluctuations are apparently related to trapped waves within the jet potential core as investigated and reported recently by other researchers. Round nozzles of three different diameters and rectangular nozzles of three different aspect ratios are studied. The pressure fluctuations manifest as a series of peaks in the spectra. These trapped wave spectral peaks are found with all nozzles. Their characteristics and variations with axial and radial distances as well as with jet Mach number are documented. Effects of initial boundary layer state and the presence of a surface nearby as well as the scaling of the frequencies of the spectral peaks are studied and discussed.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM—2019-220383 , GRC-E-DAA-TN74374
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  • 61
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    Pressure Gain Combustion for High Speed Propulsion (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-15
    Description: This presentation contains notes for a one-hour lecture that is part of a two-day AIAA Short Course titled, Hypersonic Air-Breathing Propulsion: Emerging Technologies and Cycles. The presentation covers an introduction to Pressure Gain Combustion (PGC) and its applicability to high speed airbreathing propulsion (HSABP). The concept of PGC is discussed on a thermodynamic basis, the performance benefits are demonstrated, and methods of implementation are described. These include devices such as Resonant Pulse Combustors, Internal Combustion Wave Rotors, Pulse Detonation Engines, and Rotating Detonation Engines.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN71710 , Propulsion and Energy 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN
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    NASA Electrified Aircraft Propulsion Efforts (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-14
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72959 , Hybrid/Electric Aero-Propulsion Systems for Military Applications; Oct 07, 2019 - Oct 09, 2019; Trondheim; Norway
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  • 63
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    A Control Strategy for Turbine Electrified Energy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-07
    Description: Hybrid electric propulsion architectures provide the infrastructure to enable additional benefits to the propulsion system that are otherwise unrealizable with the sole use of the current, state-of-the-art, gas-driven, turbine engines. The presence of electric machines (EMs) coupled to the shaft(s) of the turbine engine provide the ability to actively alter the operation of the engine to the benefit of the propulsion system and the aircraft it propels. This is the goal of the Turbine Electrified Energy Management (TEEM) concept, which at its broadest level addresses the management of energy across the electrified propulsion system. Prior work has demonstrated the use of this concept to alter steady-state operation and improve transient operability of a hybrid-electric propulsion system. The main benefits previously illustrated include the elimination of stability bleeds and expansion of the turbomachinery design space in order to enable more efficient designs. This paper focuses on the development of control strategies to implement the TEEM concept, and it explores several possible architecture variants for applying this concept. Comparison studies are conducted between a purely gas-driven turbofan (baseline engine configuration) and TEEM augmented variants of the baseline engine. The variants are distinguished by the shaft(s) that possess an EM. The configurations consider EMs on both shafts, an EM on the high pressure spool (HPS) only, and an EM on the low pressure spool (LPS) only. These configurations are referred to as the dual-spool configuration, the HPS configuration, and LPS configuration, respectively. The studies expose several options in configuring and controlling the system, including the use of a single EM coupled to a single shaft of a two-spool engine to positively impact the operability of both shafts. The studies also demonstrate the use of independently designed controllers for the electric machine(s) that allow for a decoupled control design process.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220353 , GRC-E-DAA-TN73066
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  • 64
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    Dynamic Analysis of the STARC-ABL Propulsion System (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-07
    Description: In the pursuit of Electrified Aircraft Propulsion (EAP), much of the attention is on the development of hybrid electric concept vehicles and their propulsion systems from a steady state performance perspective. While it is steady-state performance that largely determines the efficiency of civil air transports, engine operability and transient performance define constraints for the steady state design that impact efficiency and system viability. Neglecting dynamics and control technologies can result in an over-designed, sub optimal propulsion system or a concept that is not feasible. Thus, dynamic system studies were conducted on the propulsion system of the conceptual aircraft design known as the Single-aisle Turboelectric AiRCraft with Aft Boundary Layer propulsor (STARC-ABL). This paper describes the development of a controller to verify the baseline concept's feasibility from an operability perspective. Further, studies were conducted to identify excessive stability margin in the baseline design that could be traded for potential benefits in efficiency through an engine re design. This study revealed the potential to reduce the high pressure compressor (HPC) stall margin by 3%. Finally, a study was conducted to investigate the potential benefit of adding energy storage to the STARC-ABL concept that further improves operability and enables more gains in engine efficiency and performance. The energy storage provided an additional 0.5% stall margin can be removed from the HPC.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220352 , AIAA–2019–4182 , GRC-E-DAA-TN73064 , AIAA Propulsion and Energy Forum; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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  • 65
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    Evaluation of Electrical System Requirements for Implementing Turbine Electrified Energy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-07
    Description: Turbine Electrified Energy Management (TEEM) is a concept concerned with the management of energy in an electrified propulsion system. The management of energy in the hybrid-electric architecture has potential to benefit the turbomachinery and the aircraft it powers. The concept is particularly useful for improving operability during transient operation and could be leveraged to design a better performing engine. The concept utilizes electric machines coupled to the engine shafts and an electric power distribution system that includes energy storage. A controller is used to decide when and how energy is moved around the electrified propulsion system, particularly when considering energy conversion between mechanical and electrical forms. Prior work has shown that the electric machines can be used to supply/or extract supplemental power to/from the engine shafts to improve their operability and achieve or enable propulsion efficiency and performance benefits. However, the previous studies did not consider the practical constraints of the electrical machines and energy storage devices that are required for implementing the TEEM system architecture concept. This paper presents an integrated engine and electrical system model that is used to evaluate the electrical system requirements. The model captures the physics of the conceptual, Advanced Geared Turbofan 30,000lbf (AGTF30) engine, which features advanced technologies such as a compact gas turbine and a variable area fan nozzle. For this work, the engine is augmented with electrical system components that allow for the implementation of the TEEM concept. The evaluation presented suggests the potential of the TEEM concept to provide performance benefits for a turbofan engine.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2019-220354 , Paper AIAA–2019–4502 , GRC-E-DAA-TN73068 , AIAA/IEEE Electric Aircraft Technology Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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    Propulsion System Optimization for a Turboelectric Tiltwing Urban Air Mobility Aircraft (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-22
    Description: An emerging potential market within the aviation industry is short, frequent air taxi flights within the urban airspace. These air taxis (also called urban air mobility or UAM vehicles) are envisioned to be vertical take-o and landing designs which are capable of carrying 1 to 15 passengers in an intra-urban environment with less than 50 nautical miles of range. Numerous vehicle conceptual designs have been proposed by various industry and government organizations to fulfill these potential missions. These concepts are enabled by recent advancements in a number of areas including propulsion and power systems. While new technologies are making these vehicles possible, this new UAM design space is large, unexplored, and multidisciplinary in nature. New challenges exist in identifying and creating optimized designs for these unique vehicles with new propulsion technologies. This work presents the development of a suite of propulsion system analysis tools, which when coupled together, can improve the multidisciplinary conceptual design and optimization of UAM vehicle propulsion systems. These analysis tools are then applied to the design optimization of a turboelectric propulsion system for a notional UAM tiltwing concept. The optimization demonstration for this vehicle shows how a tightly-coupled multidisciplinary design can be developed which considers both physical design characteristics and operating schedules. Furthermore, the results explore trade-o s in the thermal management system design and how those trade-o s impact the overall vehicle.
    Keywords: Aircraft Propulsion and Power
    Type: ISABE-2019-24365 , GRC-E-DAA-TN71922 , International Society for Air Breathing Engines (ISABE) Conference; Sep 22, 2019 - Sep 27, 2019; Canberra, ACT; Australia
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  • 67
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    Dynamic Analysis of the STARC-ABL Propulsion System (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-10
    Description: In the pursuit of Electrified Aircraft Propulsion (EAP), much of the attention is on the development of hybrid electric concept vehicles and their propulsion systems from a steady state performance perspective. While it is steady-state performance that largely determines the efficiency of civil air transports, engine operability and transient performance define constraints for the steady state design that impact efficiency and system viability. Neglecting dynamics and control technologies can result in an over-designed, sub optimal propulsion system or a concept that is not feasible. Thus, dynamic system studies were conducted on the propulsion system of the conceptual aircraft design known as the Single-aisle Turboelectric AiRCraft with Aft Boundary Layer propulsor (STARC-ABL). This paper describes the development of a controller to verify the baseline concept's feasibility from an operability perspective. Further, studies were conducted to identify excessive stability margin in the baseline design that could be traded for potential benefits in efficiency through an engine re design. This study revealed the potential to reduce the high pressure compressor (HPC) stall margin by 3%. Finally, a study was conducted to investigate the potential benefit of adding energy storage to the STARC-ABL concept that further improves operability and enables more gains in engine efficiency and performance. The energy storage provided an additional 0.5% stall margin can be removed from the HPC.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72121 , AIAA Propulsion and Energy Forum 2019; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    Introduction to Dynamic Propulsion System Modeling for Control Design, Analysis, and Simulation (2019)
    In:  CASI
    Details
    Publication Date: 2019-10-19
    Description: This is an oral presentation on dynamic propulsion system modeling for control design, analysis, and simulation. These tools have been developed at NASA Glenn Research Center.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN72034 , AIAA Propulsion and Energy Forum; Aug 19, 2019 - Aug 22, 2019; Indianapolis, IN; United States
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    X-57 Maxwell Battery From Cell Level to System Level Design and Testing (2018)
    In:  CASI
    Details
    Publication Date: 2019-03-07
    Description: This presentation is on Electric and Hybrid Electric Propulsion: NASA's Approach, expectations, design and project requirements, and the motivation behind it.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN59208 , BEYOND LITHIUM ION XI; 24-26 Jul. 2018; Cleveland, OH; United States
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    Computational Investigation of a Boundary-Layer-Ingestion Propulsion System (2018)
    In:  CASI
    Details
    Publication Date: 2019-06-15
    Description: The present paper examines potential propulsive and aerodynamic benefits of integrating a Boundary-Layer Ingestion (BLI) propulsion system into the Common Research Model (CRM) geometry and the NASA Tetrahedral Unstructured Software System (TetrUSS). The Numerical Propulsion System Simulation (NPSS) environment is used to generate engine conditions for Computational Fluid Dynamics (CFD) analyses. Improvements to the BLI geometry are made using the Constrained Direct Iterative Surface Curvature (CDISC) design method. Potential benefits of the BLI system relating to cruise propulsive power are quantified using a power balance method, and a comparison to the baseline case is made. Iterations of the BLI geometric design are shown, and improvements between subsequent BLI designs are presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 feet, with Reynolds number of 40 million based on mean aerodynamic chord and an angle of attack of 2 for all geometries. Results indicate an 8% reduction in engine power requirements at cruise for the BLI configuration compared to the baseline geometry. Small geometric alterations of the aft portion of the fuselage using CDISC has been shown to marginally increase the benefit from boundary-layer ingestion further, resulting in an 8.7% reduction in power requirements for cruise, as well as a drag reduction of approximately twelve counts over the baseline geometry.
    Keywords: Aircraft Propulsion and Power
    Type: NF1676L-25357 , Journal of Aircraft (ISSN 0021-8669) (e-ISSN 1533-3868); 55; 3; 1141-1153
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    Short-Haul Revitalization Study Final Report (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A feasibility study was performed for an advanced commercial short-haul aircraft to evaluate the potential for increased service for short-haul flights that operate out of regional and community airports. An analysis of potential origin-destination markets and trip distances resulted in a seat capacity selection of 48 passengers and a design range of 600 NM. A down-select of advanced technologies resulted in a hybrid-electric propulsion system being chosen as the primary enabling technology. A conceptual design of the advanced aircraft was developed, and a mission and sizing analysis was performed, comparing variants of the advanced aircraft with different levels of electrification. Fairly aggressive levels of electrification and battery specific energy are needed for the hybridelectric architecture to realize any benefit in terms of total energy cost for the 600 NM design mission. The development and operational costs were estimated for the advanced aircraft and compared to the baseline. This analysis demonstrated the negative effect of the cost to develop the hybrid-electric technology on the eventual operating cost. A market analysis was performed to determine possible passenger demand for the advanced shorthaul aircraft. According to the market analysis, there is potential demand for such an aircraft, but not necessarily in many of the smaller regional and community airports that were the intended beneficiaries of this new aircraft concept.
    Keywords: Aircraft Propulsion and Power
    Type: NF1676L-29966 , NASA/TM-2018-219833 , L-20927
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    Hollow-Wall Heat Shield for Fuel Injector Component (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A fuel injector component includes a body, an elongate void and a plurality of bores. The body has a first surface and a second surface. The elongate void is enclosed by the body and is integrally formed between portions of the body defining the first surface and the second surface. The plurality of bores extends into the second surface to intersect the elongate void. A process for making a fuel injector component includes building an injector component body having a void and a plurality of ports connected to the void using an additive manufacturing process that utilizes a powdered building material, and removing residual powdered building material from void through the plurality of ports.
    Keywords: Aircraft Propulsion and Power
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    Efficient, Low Pressure Ratio Propulsor for Gas Turbine Engines (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A gas turbine engine includes a core flow passage, a bypass flow passage, and a propulsor arranged at an inlet of the bypass flow passage and the core flow passage. The propulsor includes a row of propulsor blades. The row includes no more than 20 of the propulsor blades. The propulsor has a pressure ratio between about 1.2 and about 1.7 across the propulsor blades.
    Keywords: Aircraft Propulsion and Power
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    Non-Axisymmetric Fixed or Variable Fan Nozzle for Boundary Layer Ingestion Propulsion (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A fan section for an engine has a fan which rotates about an axis, the fan has an inlet for ingesting ambient air, and a non-axisymmetric nozzle for providing the fan with non-uniform back pressure.
    Keywords: Aircraft Propulsion and Power
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    Meander-Like Shape Optimization of the Stator-Rotor Platform Cavity (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Recent progress in additive manufacturing has enabled opportunities to explore novel stator rim geometries which can be implemented to improve cooling strategies in turbomachinery. This paper presents a simplified stationary geometry optimization strategy to produce enhanced stator-rotor cavity sealing and highlights main driving mechanisms.The stator and rotor rims were designed using a design strategy based on inspiration from the meandering of rivers. A minimum thickness of 2 millimeters was maintained throughout the cavity to ensure a practical implementation. The computational domain comprised of the stator outlet, hub disk leakage cavity, and rotor platform was meshed using NUMECA Int. package, Hexpress. The numerical analysis required 3D Unsteady Reynolds Average Navier-Stokes to replicate vorticial structures using Ansys Fluent. The operating conditions were representative of engine-like conditions, exploring a wide range of mass flow ratios from 1 to 3 percent. The optimization yielded designs that provide 30 percent reduction in rear platform temperature while minimizing coolant mass flow. The applicability of the design was compared against 3D sector in both stationary and in rotation.
    Keywords: Aircraft Propulsion and Power
    Type: ASME GT2018-77167 , GRC-E-DAA-TN55691 , ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition (GT2018); Jun 11, 2018 - Jun 15, 2018; Oslo; Norway
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    X-57 Maxwell Battery from Cell Level to System Level Design and Testing (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The X-57 Maxwell flight demonstrator aircraft is an experimental aircraft designed to demonstrate radically improved aircraft efficiency with a 3.5 times aero-propulsive efficiency gain at a "high-speed cruise" flight condition for comparable general aviation aircraft. These gains are enabled by integrating the design of a new, optimized wing and a new electric propulsion system. There are 14 propulsors in all: 12 high lift motor that are only active during takeoff and climb, and 2 larger motors positioned on the wingtips that operate over the entire mission. The innovative electric propulsion system will have as its primary power a Li-ion battery system. Integrating a battery system into this innovative design poses unique challenges that require careful design considerations across the system. The presentation will cover a breakout of X-57 battery specifications, battery design and lessons learned when designing a high voltage battery system to power electrified aircrafts.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN59043 , GRC-E-DAA-TN59208 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Jul 12, 2018 - Jul 13, 2018; Cincinnati, OH; United States|BEYOND LITHIUM ION XI; Jul 24, 2018 - Jul 26, 2018; Cleveland, OH; United States
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    In-Line Electromagnetic Actuator for Fuel Modulation (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An in-line electromagnetic actuator with normally-open configuration has been developed for the purpose of exploring its application as a fuel modulator for the active control of combustor thermo-acoustic instabilities. The actuator is based on the spring-coil-plunger mechanism with the plunger designed to be suspended by crossed cantilever beam springs. Operational specification was set for a 1000 psi maximum inlet fuel pressure and modulation for a broad frequency bandwidth that encompasses frequencies that are typically associated with combustor thermo-acoustic instabilities. Various test results demonstrated fuel modulation up to 1200 Hz for coil excitation voltage between 2.3 and 4.6 V and current between 16 and 48 mA, respectively. The initial goal of this work was to demonstrate fuel modulation based on the concept of a normally-open fuel modulator with tethered plunger displacement.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57975 , AIAA Propulsion and Energy Forum; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
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    Aero-Propulsion Control Research in Support of NASA Aeronautics Research Strategic Thrusts (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In the past few years, NASA (National Aeronautics and Space Administration) Aeronautics Research Mission Directorate (ARMD) has introduced and updated a New Blueprint for Transforming Global Aviation . This blueprint consists of six NASA Aeronautics Research Strategic Thrusts " The updated vision is designed to ensure that through NASA's aeronautical research the United States will maintain its leadership in the sky and sustain aviation so that it remains a key economic driver and cultural touchstone for the nation. In mid-2016, technology development roadmaps were developed by ARMD for each of the strategic research thrusts and these roadmaps are continually being updated based on feedback from the broader aeronautics research community. The NASA Aeronautics research vision is implemented through a set of 4 programs " Advanced Air Vehicles Program (AAVP), Airspace Operations and Safety Program (AOSP), Integrated Aviation Systems Program (IASP), and Transformative Aeronautics Concepts Program (TACP). The Intelligent Control and Autonomy Branch (ICAB) at NASA Glenn Research Center (GRC) in Cleveland, Ohio, is leading and participating in various projects in partnership with other organizations within GRC and across NASA, the U.S. aerospace industry, and academia to develop advanced controls and health management technologies for aero-propulsion systems that will help meet the goals of the ARMD programs. These efforts are primarily under the various projects under AAVP, AOSP, and TACP. The ICAB current research tasks in support of ARMD program are described in this paper. The paper provides motivation, background, technical approach and recent accomplishments for these tasks, as well as a couple of tasks completed in the previous fiscal year.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57915 , AIAA Propulsion and Energy Forum; Jul 11, 2018 - Jul 12, 2018; Cincinnati, OH; United States
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    Design, Fabrication, and Critical Current Testing of No-Insulation Superconducting Rotor Coils for NASA's 1.4 MW High-Efficiency Megawatt Motor (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA Glenn Research Center is developing a 1.4 MW high-efficiency electric machine for future electrified aircraft to reduce energy consumption, emissions, and noise. This wound-field, synchronous machine employs a self-cooled, superconducting rotor to achieve excellent specific power and efficiency. This paper discusses the design and fabrication of the no-insulation high temperature superconducting (HTS) rotor coils and compares them to conventionally insulated HTS coils. Two sub-scale test coils with epoxy on only one axial face were fabricated. Critical current testing of the coils at 77 K and self field was conducted to study the influence of thermal cycling on their critical current and n-value. After two or four aggressive thermal cycles between 77 K and about 278 K (5 degree C), the critical current and n-value were nearly unchanged, indicating very little to no degradation.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57803 , AIAA Propulsion & Energy; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
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    Pressure-Gain Combustion for Gas Turbines (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Pressure Gain Combustion (PGC) is under investigation as a means to improve the thermal efficiency of gas turbines. PGC is a fundamentally unsteady combustion process which, through some means of confinement, raises the total pressure of the working fluid relative to the initial process state. When implemented in a combustor it yields a total pressure gain across the device instead of the typical loss seen in a conventional combustor. This pressure gain can significantly improve gas turbine performance. The tutorial will provide an introduction to the concept of PGC. It will begin with a process description in fundamental thermodynamic terms, and will quantify potential benefits. The majority of the presentation will describe the various approaches to implementation that are under investigation by the PGC.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN55268 , ASME 2018 Turbo Expo; Jun 11, 2018 - Jun 15, 2018; Lillestrom; Norway
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    Propulsion-Airframe Integration Technical Interchange Meeting (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The 1st Propulsion-Airframe Integration Technical Interchange Meeting (PAITIM) was held in Cleveland, Ohio, at the Ohio Aerospace Institute from May 30 to 31, 2018. The meeting was organized by representatives from the National Aeronautics and Space Administration (NASA) aeronautics research centers (i.e., Ames Research Center, Armstrong Flight Research Center, Glenn Research Center, and Langley Research Center) and the Air Force Research Laboratory and was sponsored by NASAs Advanced Air Vehicle Technology project. The purpose of the PAI-TIM was to exchange information and ideas amongst this community of researchers in a workshop-type setting. At this meeting, results were shared in the form of presentations only (i.e., no papers were required) regarding ongoing research efforts in both the experimental and modeling areas associated with propulsion-airframe integration for advanced subsonic and supersonic vehicles. During the 2-day meeting, a total of 22 presentations were made and were organized into three sessions: (1) Vision and PAI Challenges of Future Air Vehicles, (2) PAI Modeling and Simulation: State-of-the-Art and Challenges/Needs, and (3) PAI Testing: Test Techniques, Results and Challenges/Needs. All but two of the presentations made at the PAI-TIM are included in this publicly available conference proceedings document.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CP-2018-219955 , E-19566 , GRC-E-DAA-TN58510 , Propulsion-Airframe Integration Technical Interchange Meeting (PAI-TIM); May 30, 2018 - May 31, 2018; Cleveland, OH; United States
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    Health Monitoring and Prognostics for More Electric Aircrafts (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As more and more electric vehicles emerge in our daily operation progressively, a very critical challenge lies in the prediction of remaining flying time/distance (for aircraft). This information is important, particularly in the case of unmanned vehicles, because such vehicles can become self-aware, autonomously compute its own capabilities, and identify how to best plan and successfully complete vehicular missions safely. In case of electric aircrafts, computing remaining flying time is also safety-critical, since an aircraft that runs out of battery charge while in the air will eventually lose control leading to catastrophe. In order to tackle and solve the prediction problem, it is essential to have awareness of the current state and health of the system, especially since it is necessary to perform condition-based predictions. To be able to predict the future state of the system, it is also required to possess knowledge of the current and future operations of the vehicle. Given models of the current and future system behavior, the general approach of model-based prognostics can be employed as a solution to the prior stated prediction problem.For electric aircraft, propulsion is based on power generated from batteries. Thus, it is critical to monitor battery state charge and to estimate the ability of the battery to support mission activities as it is being discharged during flight operation. The ability of the vehicle to complete its given mission very much depends on the charge left in the batteries based on its operational route, maneuvering, weather conditions along with aging health of the batteries. Hence, for the purpose this discussion, consider the scenario of an unmanned electric aircraft that has some planned sequence of waypoints to reach throughout its mission. In such a scenario, for this particular aircraft, and within the region it is flown, at most two minutes are required to safely land the aircraft. Thus, it is desired to predict at which point in time the aircraft must begin to head to the runway and land.
    Keywords: Aircraft Propulsion and Power
    Type: ARC-E-DAA-TN60957 , More Electric Aircrafts Europe 2018; Oct 23, 2018 - Oct 25, 2018; Hamburg; Germany
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    Determining the Pressure Gain of Pressure Gain Combustion (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Over the past few decades, there has been significant research into propulsion concepts attempting to employ pressure gain combustion. Pressure gain combustion concepts to date have resulted in dynamic, non-uniform gas flows which are difficult to characterize and compare with more conventional forms of propulsion. This paper proposes a technique to derive for the pressure gain combustion device an equivalent, steady, uniform gas pressure that is available to do work or provide thrust, thereby providing a direct comparison with conventional propulsive devices.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57340 , AIAA Propulsion & Energy 2018; Jul 07, 2018 - Jul 13, 2018; Cincinnati, OH; United States
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    Electric Motor Noise from Small Quadcopters: Part 1 - Acoustic Measurements (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II - Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57550 , AIAA/CEAS Aeroacoustics Conference; Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
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    Turbo-Generation Control (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Electrified Aircraft Propulsion (EAP) power systems are being studied at the NASA Electric Aircraft Testbed (NEAT) facility. The electric motors at NEAT have the capability to dynamically respond to commands that would be unrealistic when integrated with turbomachinery. There is a need to provide more realistic turbine transients for future system performance studies.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57418 , External Meeting with Boeing; Jun 05, 2018; Cleveland, OH; United States
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    Electric Motor Noise from Small Quadcopters (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The increased interest in electric motors for propulsion systems has driven interest in quantifying the contribution of electric motor noise to the overall sound levels and possible human annoyance of the propulsion system. This work presents acoustic measurements of electric motors used for small quadcopters to quantify the sound produced by a number of outrunning motors with different types of controllers. Results are presented for loaded and unloaded motors as installed and uninstalled configurations. Motor resonance frequencies were measured and computed. Current probe measurements showed that the supply current from the controllers contained significant harmonic content for the conventional and sinewave controllers. Acoustic results showed motor noise is typically radiated at frequencies near the mode 2 vibration frequency at roughly 5000 Hz. Electric motor noise was evident in the spectra produced by many of the motor-controller combinations for motors loaded with propellers with levels often greater than those for the motor alone due to increase in the stator magnetic flux density with increased current. An installed configuration produced increases in acoustic radiation over that of the uninstalled motor in a frequency range near the mode 1 vibration frequency near 1200 Hz. A companion paper (Part I - Acoustic Measurements), focuses on source identification using a phased array and directivity characteristics for a baseline configuration.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56339 , AIAA Aviation Forum 2018; Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
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    LEAPTech/HEIST Experiment Test and Evaluation Summary (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Leading Edge Asynchronous Propeller Technology (LEAPTech) project tested the Hybrid-Electric Integrated Systems Testbed (HEIST) and was intended for a general aviation sized aircraft with Distributed Electric Propulsion (DEP) to show large improvements with regards to efficiency, emissions, safety and operating costs. The wing was designed for high loading to improve ride quality and show improved takeoff and landing characteristics. The full-scale test article wing had a 31-foot-span, had integrated electric motors, was mounted on a truck 20 ft. above ground and driven in a simulated flight test environment at various velocities up to 70 miles per hour. The simulated flight test varied primarily angle of attack and flap settings. These tests were conducted to obtain data and verify blown wing performance primarily with regards to lift. The experimental test results are presented.
    Keywords: Aircraft Propulsion and Power
    Type: AFRC-E-DAA-TN48263 , AIAA Aviation and Aeronautics Forum (Aviation 2018); Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
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    Aerodynamic Design and Optimization of Fan Stage for Boundary Layer Ingestion Propulsion System (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The present paper addresses the process of preliminary design of a low-pressure fan and outlet guide vane (OGV) of a boundary layer ingestion (BLI) propulsion system. The tail-cone thruster systems of NASA's STARC_ABL (Single-aisle Turboelectric Aircraft with an Aft Boundary-Layer propulsor) adopts an axi-symmetric BLI type inlet as opposed to other embedded engine systems. Thus, the focus of the present work is placed on maximizing the efficiency of the fan and OGV stages under a significant radial distortion. A parameterization with B-spline function for camber line angles, metal chord, thickness distribution and stacking axis of blades is presented. The flowpath lines are also parameterized by B-spline function and aggregated in the design system of blades. The design optimization with evolutionary algorithm is performed with constraints of fan pressure ratio, OGV exit swirl angle and nozzle exit properties. The inlet conditions for the turbo-machinery CFD (Computational Fluid Dynamics) domain and the design goal of the fan stage are driven by a propulsion airframe integration (PAI) model that uses a 3-D unstructured RANS (Reynolds Average Navier Stokes) solver and actuator disk model. The expected power saving of the BLI propulsor is quantified via PAI analysis and the resulting preliminary design of the fan stages is compared with a clean-inlet flow propulsor.
    Keywords: Aircraft Propulsion and Power
    Type: ICCFD10-091 , GRC-E-DAA-TN58523 , International Conference on Computational Fluid Dynamics (ICCFD 10); Jul 09, 2018 - Jul 13, 2018; Barcelona; Spain
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    Modeling and Control Design for a Turboelectric Single Aisle Aircraft Propulsion System (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A nonlinear dynamic model with full flight envelope controller is developed for the propulsion system of a partially turboelectric single-aisle aircraft. The propulsion system model consists of two turbofan engines with a large percentage of power extraction, feeding an electric tail fan for boundary layer ingestion. The dynamic model is compared against an existing steady state design model. An electrical system model using a simple power flow approach is integrated into existing modeling tools used for dynamic simulation of the turbomachinery of the vehicle. In addition to the simple power flow model of the electrical system, a more detailed model is used for comparison at a key vehicle transient flight condition. The controller is a gain scheduled proportional-integral type that is examined throughout the flight envelope for performance metrics such as rise time and operability margins. Potential improvements in efficiency for the vehicle are explored by adjusting the power split between the energy used for thrust by the turbofans and that extracted to supply power to the tail fan. Finally, an operability study of the vehicle is conducted using a 900 nautical mile mission profile for a nominal vehicle configuration, a deteriorated propulsion system at the end of its operating life, and an optimized power schedule with improved efficiency.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58010 , AIAA Propulsion and Energy - IEEE Electric Aircraft Technologies Symposium; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
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    Resonant Pulse Combustors: A Reliable Route to Practical Pressure Gain Combustion (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Pressure Gain Combustion (PGC) defined: A fundamentally unsteady process whereby gas expansion by heat release is constrained, causing a rise in stagnation pressure and allowing work extraction by expansion to the initial pressure. A particular type of pressure gain combustion (PGC) device is described, which is under investigation at GRC (Glenn Research Center). The Resonant Pulse Combustor (RPC) has been largely overlooked due to its theoretically low performance. However, its practical performance is quite competitive with other PGC systems, and its physical simplicity is unmatched.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58478 , Active Flow and Combustion Control (AFCC 2018); Sep 19, 2018 - Sep 21, 2018; Berlin; Germany
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    Active Turbine Tip Clearance Control Trade Space Analysis of an Advanced Geared Turbofan Engine (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Tip clearance within the high pressure turbine of a gas turbine engine is a significant factor in engine performance and efficiency. In the pursuit of higher efficiency, aero-engine designs are migrating toward compact gas turbine (CGT) technology that seeks to increase the bypass ratio of the gas turbine engine without increasing the size of the fan, which is constrained by its underwing location. The reduced size of CGTs invoke concern over increased sensitivity of engine performance due to turbine tip clearance gap that makes an argument for advanced tip clearance mitigation and control techniques to be employed. This paper evaluates the tip clearance trade space for a conceptual geared turbofan engine with a CGT core. This is accomplished through a modeling and simulation approach that includes a sensitivity analysis of engine performance in response to high pressure turbine tip clearance as well as an evaluation of the sensitivity of tip clearance to various design parameters, including material properties and component cooling characteristics. Also included is a parametric study of actuators that provides preliminary requirements for implementation of active turbine tip clearance control actuation systems. The results produced from these studies are meant to be informative, with special emphasis on the demonstration of a systematic approach. The modeling approach appears to capture expected trends. The studies suggest that the tip clearance gap will have a greater impact on the new CGT engines and that a relatively slow, actively controlled actuation system may be sufficient as long as it has control authority to both open and close the tip clearance gap.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58715 , AIAA Propulsion and Energy Forum; Jul 09, 2018 - Jul 11, 2018; Cincinnati, Ohio; United States
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    Thermal Modeling of an Advanced Geared Turbofan for Distributed Engine Control Application (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Reliability and life-expectancy of gas turbine engine components is very much correlated to the temperature environment in which they operate. This is no different for control system components, especially those with electronic parts. In recent years, the concept of Distributed Engine Control (DEC) has emerged to address the limitations of the current centralized control implementation. This new approach involves relocating control system components from a relatively benign environment to the harsher thermal environment of the engine casing and its surrounding structures and cavities. In this paper, an approach to modeling the gas turbine thermal environment is described. The modeling approach is applied to a 3rd generation geared turbofan design with a focus on the engine locations where control instrumentation and actuation could be installed. The analysis was conducted with an eye toward component reliability and service life as it relates to the thermal environment. The results were found to be reasonable. Furthermore, the model is shown to execute in real-time within a multi-model simulation environment that demonstrates the capability to interact with hardware to drive test equipment.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58712 , AIAA Propulsion and Energy Forum; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
    Format: application/pdf
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    Optimization of an Air Core Dual Halbach Array Axial Flux Rim Drive for Electric Aircraft (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The anticipated development of the on-demand-mobility (ODM) market has accelerated the development of electric aircraft. Most proposed electric aircraft have propulsion systems that consist of fans directly driven by electric motors. The lower complexity of these propulsion systems opens the door to more custom propulsion system designs that are tailored to a given aircraft and its mission. This paper represents initial steps in the development of an electric propulsion system design code. A proof of concept version of the code is presented. The proof of concept version of the code is for the design of an axial flux rim driven propulsion system. NASA's all electric aircraft X-57, is used as a case study for this design code. The results of this case study are used to discuss the feasibility and potential benefits of using an axial flux rim driven propulsor on X-57. The final result of the case study shows a potential 4km increase in range over the current design.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56733 , AIAA Aviation Forum; Jun 23, 2018 - Jun 29, 2018; Atlanta, GA; United States
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    NASA Propulsion Capability Leadership (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Aircraft Propulsion and Power
    Type: M18-6681 , Rocket Propulsion for the 21st Century (RP21) Steering Committee Meeting; May 15, 2018 - May 16, 2018; Arlington, VA; United States
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    Low-Noise Operating Mode for Propeller-Driven Electric Airplanes (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Mechanical shaft power and shaft speed of reciprocating internal combustion engines are closely coupled. Maximum rated shaft power is typically produced at or near peak shaft speed. If a general aviation airplane equipped with a reciprocating engine and a variable-pitch propeller attempts a low-noise takeoff by reducing propeller tip speed, propeller power and thrust are reduced. Such takeoffs are not tolerated due to punishing performance effects, such as increased field lengths and poor climb rates. Certain electric motors, however, are able to deliver maximum shaft power over a wide range of shaft speed. Electric or hybrid-electric propeller-driven airplanes should be able to exploit this behavior. At low shaft speeds, high shaft power levels and high blade pitch angles could be combined to recover much of the thrust that would otherwise be lost. This could enable a low-noise operating mode for propellers normally designed for performance rather than for noise. The subject of this paper is an analytical investigation into low-noise takeoffs and steady overflights of a notional general aviation airplane equipped with a propeller driven by an electric motor.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56724 , AIAA Aviation Forum; Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
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    DGEN Aeropropulsion Research Turbofan (DART): Lossless Projection of Measured Engine Noise Spectra to a 1-Foot-Radius Arc (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Baseline noise and aerodynamic data have been acquired for the DGEN Aeropropulsion Research Turbofan (DART) test rig. The DART is a fully-mobile engine test rig featuring a DGEN380 geared turbofan producing approximately 500 lbs. of thrust at sea level and a self-contained control room. Baseline noise data were acquired using 5 microphone arrays, varying distance, configuration, and angle to reflect the measurement locations at several other test facilities. Noise data were acquired at one array location on each test day to establish the repeatability of the measurements. The noise data from the different arrays is analyzed to show the limitations of projecting the results to a common radius when the noise sources are distributed and the measurement location is not in the geometric far-field.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56602 , AIAA Aviation Forum 2018; Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
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    Electric Motor Noise for Small Quadcopters: Part I - Acoustic Measurements (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56469 , AIAA Aviation Forum 2018; Jun 25, 2018 - Jun 29, 2018; Atlanta,GA; United States
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  • 98
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    Resonance and Tones in Dual-Stream Nozzle Flows (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A dual-stream nozzle configuration was studied numerically with the objective of predicting the appearance of tones and study their sources. It was found that some of the tones traced to a coupling between Strouhal shedding from the struts, which held different pieces of the nozzle together, and various duct acoustic modes. A focus of the work was on exploring the nature of the duct modes. First, elements of the numerical procedure were studied for a 4-strut nozzle, validating the results with existing experimental data. The approach was then applied to a 3-strut geometry and four different excitation methods. The predicted tones and associated duct modes are analyzed in detail.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56368 , AIAA Aviation 2018; Jun 25, 2018 - Jun 29, 2018; Atlanta, GA; United States
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  • 99
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    Two-Speed Rotorcraft Research Transmission Power-Loss Associated with the Lubrication and Hydraulic Rotating Feed-Through Design Feature (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An investigation was completed into the power loss associated with a rotating feed-through (RFT) design feature used to transfer lubrication and a hydraulic control signal from the static reference frame to a rotating reference frame in the NASA GRC two-speed transmission tests conducted in the Variable-Speed Drive Test Rig. The RFT feature, not commercially available, was created specifically for this research project and is integral to all two-speed transmission configurations tested, as well as a variant concept design for a geared variable-speed transmission presented at AHS Forum 71 in 2015. The experimental set-up and results from measurements in the isolated rotating-feed-through (RFT) experiments are presented. Results were used in an overall power loss assessment for a scaled conceptual 1,000 horsepower inline concentric two-speed transmission to support a NASA Revolutionary Vertical Lift Technologies (RVLT) Technical Challenge, demonstrating 50% speed change with less than 2% power loss while maintaining current power-to-weight ratios.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN54677 , American Helicopter Society (AHS) Forum; May 14, 2018 - May 17, 2018; Phoenix, AZ; United States
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    An Approach for Utilizing Power Flow Modeling for Simulations of Hybrid Electric Propulsion Systems (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes an approach to creating simulations of the electric components for a hybrid electric propulsion system. The proposed modeling technique is based on power/load flow modeling and is designed to provide a modular framework that includes buses, lines, and other electrical components that can be connected together to form the electrical distribution system. The purpose of this paper is to detail an electric distribution system modeling technique and to demonstrate how these models may be integrated with turbomachinery simulations. These general modeling techniques were created to be utilized for system and control design studies. Additionally, steady-state and dynamic performance for a proposed model example is compared with data from a hardware in the loop simulation.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN56356 , AIAA/IEEE Electric Aircraft Technologies Symposium (EATS); Jul 12, 2018 - Jul 13, 2018; Cincinnati, OH; United States
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