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  • Inorganic Chemistry  (3,367)
  • Matter waves and collective properties of cold atoms and molecules  (1,760)
  • Aircraft Propulsion and Power
  • Industrial Chemistry
  • 2015-2019  (2,065)
  • 1950-1954  (2,969)
  • 1915-1919
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  • 1
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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
    Format: application/pdf
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  • 2
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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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  • 3
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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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  • 4
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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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  • 5
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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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  • 6
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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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  • 7
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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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  • 8
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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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  • 9
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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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  • 10
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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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  • 11
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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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  • 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 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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  • 13
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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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  • 14
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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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  • 15
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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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  • 16
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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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  • 17
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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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  • 18
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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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  • 19
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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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  • 20
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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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  • 21
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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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  • 22
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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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    NASA TECHNICAL REPORTS
  • 23
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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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  • 24
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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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    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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    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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    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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    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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    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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    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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    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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  • 63
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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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  • 65
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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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    Attractive Fermi polarons at nonzero temperatures with a finite impurity concentration (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-07-26
    Description: Author(s): Hui Hu, Brendan C. Mulkerin, Jia Wang, and Xia-Ji Liu We theoretically investigate how quasiparticle properties of an attractive Fermi polaron are affected by nonzero temperature and finite impurity concentration in three dimensions and in free space. By applying both non-self-consistent and self-consistent many-body T -matrix theories, we calculate the... [Phys. Rev. A 98, 013626] Published Wed Jul 25, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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    Spin-1 topological monopoles in the parameter space of ultracold atoms (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-07-27
    Description: Author(s): Haiping Hu and Chuanwei Zhang A magnetic monopole is a hypothetical elementary particle with an isolated magnetic pole. Its existence would directly lead to the quantization of electric charges. In recent years, analogs of magnetic monopoles, represented by topological defects in parameter spaces, have been studied in a wide ran... [Phys. Rev. A 98, 013627] Published Thu Jul 26, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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    Topological invariants in dissipative extensions of the Su-Schrieffer-Heeger model (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-07-28
    Description: Author(s): Felix Dangel, Marcel Wagner, Holger Cartarius, Jörg Main, and Günter Wunner We investigate dissipative extensions of the Su-Schrieffer-Heeger model with regard to different approaches of modeling dissipation. In doing so, we use two distinct frameworks to describe the gain and loss of particles: One uses Lindblad operators within the scope of Lindblad master equations, and ... [Phys. Rev. A 98, 013628] Published Fri Jul 27, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Many-body stabilization of a resonant $p$-wave Fermi gas in one dimension (2018)
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    Publication Date: 2018-07-31
    Description: Author(s): Lei Pan, Shu Chen, and Xiaoling Cui Using the asymptotic Bethe ansatz, we study the stabilization problem of the one-dimensional spin-polarized Fermi gas confined in a hard-wall potential with a tunable p -wave scattering length and finite effective range. We find that the interplay of two factors, i.e., the finite interaction range an... [Phys. Rev. A 98, 011603(R)] Published Mon Jul 30, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 71
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    Born-Bogoliubov-Green-Kirkwood-Yvon hierarchy for ultracold bosonic systems (2018)
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    Publication Date: 2018-07-31
    Description: Author(s): Sven Krönke and Peter Schmelcher We establish a theoretical framework for exploring the quantum dynamics of finite ultracold bosonic ensembles based on the Born-Bogoliubov-Green-Kirkwood-Yvon (BBGKY) hierarchy for equations of motion for few-particle reduced density matrices (RDMs). The theory applies to zero as well as low tempera... [Phys. Rev. A 98, 013629] Published Mon Jul 30, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 72
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    Spin-orbit-coupled soliton in a random potential (2018)
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    Publication Date: 2018-08-07
    Description: Author(s): Sh. Mardonov, V. V. Konotop, B. A. Malomed, M. Modugno, and E. Ya. Sherman We investigate theoretically the dynamics of a spin-orbit-coupled soliton formed by a self-interacting Bose-Einstein condensate immersed in a random potential, in the presence of an artificial magnetic field. We find that, due to the anomalous spin-dependent velocity, the synthetic Zeeman coupling c... [Phys. Rev. A 98, 023604] Published Mon Aug 06, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 73
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    Post-Ehrenfest many-body quantum interferences in ultracold atoms far out of equilibrium (2018)
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    Publication Date: 2018-06-15
    Description: Author(s): Steven Tomsovic, Peter Schlagheck, Denis Ullmo, Juan-Diego Urbina, and Klaus Richter Far out-of-equilibrium many-body quantum dynamics in isolated systems necessarily generates interferences beyond an Ehrenfest timescale, where quantum and classical expectation values diverge. Of great recent interest is the role these interferences play in the spreading of quantum information acros... [Phys. Rev. A 97, 061606(R)] Published Thu Jun 14, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 74
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    Nonlocal pair correlations in Lieb-Liniger gases: A unified nonperturbative approach from weak degeneracy to high temperatures (2018)
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    Publication Date: 2018-06-16
    Description: Author(s): Benjamin Geiger, Quirin Hummel, Juan Diego Urbina, and Klaus Richter We present analytical results for the nonlocal pair correlations in one-dimensional bosonic systems with repulsive contact interactions that are uniformly valid from the classical regime of high temperatures down to weak quantum degeneracy entering the regime of ultralow temperatures. By using the i... [Phys. Rev. A 97, 063612] Published Fri Jun 15, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 75
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    Wigner function of noninteracting trapped fermions (2018)
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    Publication Date: 2018-06-16
    Description: Author(s): David S. Dean, Pierre Le Doussal, Satya N. Majumdar, and Grégory Schehr The Wigner function is studied for trapped noninteracting fermions. Universal scaling behavior of the function, independent of the trapping potential and the spatial dimension, is found at both zero and finite temperatures. [Phys. Rev. A 97, 063614] Published Fri Jun 15, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 76
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    Dimer-dimer zero crossing and dilute dimerized liquid in a one-dimensional mixture (2018)
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    Publication Date: 2018-06-16
    Description: Author(s): A. Pricoupenko and D. S. Petrov We consider the system of dimers formed in a one-dimensional mass-balanced Bose-Bose mixture of species σ = ↑ , ↓ with attractive interspecies and repulsive intraspecies contact interactions. In the plane parametrized by the ratios of the coupling constants g ↑ ↑ / | g ↑ ↓ | and g ↓ ↓ / | g ↑ ↓ | we trace out the curve... [Phys. Rev. A 97, 063616] Published Fri Jun 15, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 77
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    Dimensional crossover for the beyond-mean-field correction in Bose gases (2018)
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    Publication Date: 2018-11-27
    Description: Author(s): Tobias Ilg, Jan Kumlin, Luis Santos, Dmitry S. Petrov, and Hans Peter Büchler We present a detailed beyond-mean-field analysis of a weakly interacting Bose gas in the crossover from three to low dimensions. We find an analytical solution for the energy and provide a clear qualitative picture of the crossover in the case of a box potential with periodic boundary conditions. We... [Phys. Rev. A 98, 051604(R)] Published Mon Nov 26, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 78
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    Order parameter and detection for a finite ensemble of crystallized one-dimensional dipolar bosons in optical lattices (2018)
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    Publication Date: 2018-11-27
    Description: Author(s): Budhaditya Chatterjee and Axel U. J. Lode We explore the ground-state properties of a few bosons with dipole-dipole interactions in a one-dimensional optical lattice. For comparatively strong interactions, a transition from a Mott-insulator state to a crystal state occurs. Herein, we provide a detailed characterization and a detection proto... [Phys. Rev. A 98, 053624] Published Mon Nov 26, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 79
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    Chiral Majorana edge states in the vortex core of a $p+ip$ Fermi superfluid (2018)
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    Publication Date: 2018-11-28
    Description: Author(s): Jing-Bo Wang, Wei Yi, and Jian-Song Pan We study Majorana modes in the vortex core of a two-dimensional p + i p Fermi superfluid interacting with a Bose-Einstein condensate. Under a repulsive s -wave contact interaction between fermions and bosons, fermions are depleted from the vortex core when the bosonic density becomes sufficiently high. ... [Phys. Rev. A 98, 053630] Published Tue Nov 27, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 80
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    Generating macroscopic superpositions with interacting Bose-Einstein condensates: Multimode speedups and speed limits (2018)
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    Publication Date: 2018-12-05
    Description: Author(s): Samuel P. Nolan and Simon A. Haine We theoretically investigate the effect of multimode dynamics on the creation of macroscopic superposition states (spin-cat states) in Bose-Einstein condensates via one-axis twisting. A two-component Bose-Einstein condensate naturally realizes an effective one-axis twisting interaction, under which ... [Phys. Rev. A 98, 063606] Published Tue Dec 04, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 81
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    Quantum reflection of rare-gas atoms and clusters from a grating (2018)
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    Publication Date: 2018-12-05
    Description: Author(s): G. Rojas-Lorenzo, J. Rubayo-Soneira, S. Miret-Artés, and E. Pollak Quantum reflection is a universal property of atoms and molecules when scattered from surfaces in ultracold collisions. Recent experimental work has documented the quantum reflection and diffraction of He atoms, dimers, trimers, and neon atoms when reflected from a grating. Conditions for the observ... [Phys. Rev. A 98, 063604] Published Tue Dec 04, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 82
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    Gauge-potential-induced rotation of spin-orbit-coupled Bose-Einstein condensates (2018)
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    Publication Date: 2018-12-05
    Description: Author(s): Jingjing Jin, Wei Han, and Suying Zhang We demonstrate that a spin-orbit-coupled Bose-Einstein condensate can be effectively rotated by adding a real magnetic field to inputting gauge angular momentum, which is distinctly different from the traditional ways of rotation by stirring or Raman laser dressing to inputting canonical angular mom... [Phys. Rev. A 98, 063607] Published Tue Dec 04, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 83
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    Topological edge states in Rashba-Dresselhaus spin-orbit-coupled atoms in a Zeeman lattice (2018)
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    Publication Date: 2018-12-08
    Description: Author(s): C. Li, F. Ye, X. Chen, Y. V. Kartashov, L. Torner, and V. V. Konotop We address the impact of spin-orbit coupling on the existence and properties of topological edge states of cold neutral atoms and Bose-Einstein condensates loaded in honeycomb Zeeman lattices—lattices where the spinor components are placed in potentials having opposite signs. We find that the type o... [Phys. Rev. A 98, 061601(R)] Published Fri Dec 07, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Measuring the local gravitational field using survival resonances in a dissipatively driven atom-optics system (2018)
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    Publication Date: 2018-12-11
    Description: Author(s): Shijie Chai, Julia Fekete, and Mikkel F. Andersen We do a proof-of-principle demonstration of an atomic gravimeter based on survival resonances of dissipatively driven atoms. Exposing laser-cooled atoms to a sequence of near-resonant standing-wave light pulses reveals survival resonances when the standing-wave interference pattern accelerates. The ... [Phys. Rev. A 98, 063614] Published Mon Dec 10, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 85
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    Stabilizing Fulde-Ferrell-Larkin-Ovchinnikov superfluidity with long-range interactions in a mixed-dimensional Bose-Fermi system (2018)
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    Publication Date: 2018-07-25
    Description: Author(s): Jonatan Melkær Midtgaard and Georg M. Bruun We analyze the stability of inhomogeneous superfluid phases in a system consisting of identical fermions confined in two layers that are immersed in a Bose-Einstein condensate (BEC). The fermions in the two layers interact via an induced interaction mediated by the BEC, which gives rise to pairing. ... [Phys. Rev. A 98, 013624] Published Tue Jul 24, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Diffusion of quantum vortices (2018)
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    Publication Date: 2018-08-08
    Description: Author(s): E. Rickinson, N. G. Parker, A. W. Baggaley, and C. F. Barenghi We determine the evolution of a cluster of quantum vortices initially placed at the center of a larger vortex-free region. We find that the cluster spreads out spatially. This spreading motion consists of two effects: the rapid evaporation of vortex dipoles from the cluster and the slow expansion of... [Phys. Rev. A 98, 023608] Published Tue Aug 07, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 87
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    Vortex patterns and the critical rotational frequency in rotating dipolar Bose-Einstein condensates (2018)
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    Publication Date: 2018-08-11
    Description: Author(s): Yongyong Cai, Yongjun Yuan, Matthias Rosenkranz, Han Pu, and Weizhu Bao Based on the two-dimensional mean-field equations for pancake-shaped dipolar Bose-Einstein condensates in a rotating frame, for both attractive and repulsive dipole-dipole interaction (DDI) as well as arbitrary polarization direction, we study the profiles of the single vortex state and show how the... [Phys. Rev. A 98, 023610] Published Fri Aug 10, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 88
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    Dynamical quantum phase transitions in systems with broken continuous time and space translation symmetries (2018)
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    Publication Date: 2018-08-14
    Description: Author(s): Arkadiusz Kosior, Andrzej Syrwid, and Krzysztof Sacha Spontaneous breaking of continuous time translation symmetry into a discrete one is related to time crystal formation. While the phenomenon is not possible in the ground state of a time-independent many-body system, it can occur in an excited eigenstate. Here, we concentrate on bosons on a ring with... [Phys. Rev. A 98, 023612] Published Mon Aug 13, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 89
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    Nonperturbative method to compute thermal correlations in one-dimensional systems (2018)
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    Publication Date: 2018-08-14
    Description: Author(s): Stefan Beck, Igor E. Mazets, and Thomas Schweigler We develop a highly efficient method to numerically simulate thermal fluctuations and correlations in nonrelativistic continuous bosonic one-dimensional systems. The method is suitable for arbitrary local interactions as long as the system remains dynamically stable. We start by proving the equivale... [Phys. Rev. A 98, 023613] Published Mon Aug 13, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Numerical study of the chiral ${\mathbb{Z}}_{3}$ quantum phase transition in one spatial dimension (2018)
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    Publication Date: 2018-08-14
    Description: Author(s): Rhine Samajdar, Soonwon Choi, Hannes Pichler, Mikhail D. Lukin, and Subir Sachdev Recent experiments on a one-dimensional chain of trapped alkali-metal atoms [Bernien et al. , Nature (London) 551 , 579 (2017) ] have observed a quantum transition associated with the onset of period-3 ordering of pumped Rydberg states. This spontaneous Z 3 symmetry breaking is described by a constrain... [Phys. Rev. A 98, 023614] Published Mon Aug 13, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 91
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    Vortices in self-bound dipolar droplets (2018)
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    Publication Date: 2018-08-16
    Description: Author(s): André Cidrim, Francisco E. A. dos Santos, Emanuel A. L. Henn, and Tommaso Macrì Quantized vortices have been observed in a variety of superfluid systems, from He 4 to condensates of alkali-metal bosons and ultracold Fermi gases along the BEC-BCS crossover. In this article we study the stability of singly quantized vortex lines in dilute dipolar self-bound droplets. We first disc... [Phys. Rev. A 98, 023618] Published Wed Aug 15, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 92
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    Emergence of continuous rotational symmetries in ultracold atoms coupled to optical cavities (2018)
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    Publication Date: 2018-08-16
    Description: Author(s): E. I. Rodríguez Chiacchio and A. Nunnenkamp We investigate the physics of a gas of ultracold atoms coupled to three single-mode optical cavities and transversely pumped with a laser. Recent work has demonstrated that, for two cavities, the Z 2 symmetries of each cavity can be combined into a global U(1) symmetry [J. Léonard et al. , Nature (Lon... [Phys. Rev. A 98, 023617] Published Wed Aug 15, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Macroscopic quantum escape of Bose-Einstein condensates: Analysis of experimentally realizable quasi-one-dimensional traps (2018)
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    Publication Date: 2018-08-16
    Description: Author(s): Diego A. Alcala, Gregor Urban, Matthias Weidemüller, and Lincoln D. Carr The variational JWKB method is used to determine experimentally accessible macroscopic quantum tunneling regimes of quasibound Bose-Einstein condensates in two quasi-one-dimensional trap configurations. The potentials can be created by magnetic and optical traps: a symmetric trap from two offset Gau... [Phys. Rev. A 98, 023619] Published Wed Aug 15, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Correlated spin-flip tunneling in a Fermi lattice gas (2018)
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    Publication Date: 2018-08-21
    Description: Author(s): Wenchao Xu, William Morong, Hoi-Yin Hui, Vito W. Scarola, and Brian DeMarco We report the realization of correlated, density-dependent tunneling for fermionic K 40 atoms trapped in an optical lattice. By appropriately tuning the frequency difference between a pair of Raman beams applied to a spin-polarized gas, simultaneous spin transitions and tunneling events are induced t... [Phys. Rev. A 98, 023623] Published Mon Aug 20, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 95
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    Charge density wave and charge pump of interacting fermions in circularly shaken hexagonal optical lattices (2018)
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    Publication Date: 2018-09-07
    Description: Author(s): Tao Qin, Alexander Schnell, Klaus Sengstock, Christof Weitenberg, André Eckardt, and Walter Hofstetter We analyze strong correlation effects and topological properties of interacting fermions with a Falicov-Kimball-type interaction in circularly shaken hexagonal optical lattices, which can be effectively described by the Haldane-Falicov-Kimball model, using the real-space Floquet dynamical mean-field... [Phys. Rev. A 98, 033601] Published Thu Sep 06, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Multiparameter estimation via an ensemble of spinor atoms (2018)
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    Publication Date: 2018-09-12
    Description: Author(s): Min Zhuang, Jiahao Huang, and Chaohong Lee Multiparameter estimation, which aims to simultaneously determine multiple parameters in the same measurement procedure, attracts extensive interest in measurement science and technologies. Here, we propose a multimode many-body quantum interferometry for simultaneously estimating linear and quadrat... [Phys. Rev. A 98, 033603] Published Tue Sep 11, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Accessing finite-momentum excitations of the one-dimensional Bose-Hubbard model using superlattice-modulation spectroscopy (2018)
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    Publication Date: 2018-09-15
    Description: Author(s): Karla Loida, Jean-Sébastien Bernier, Roberta Citro, Edmond Orignac, and Corinna Kollath We investigate the response to superlattice modulation of a bosonic quantum gas confined to arrays of tubes emulating the one-dimensional Bose-Hubbard model. We demonstrate, using both time-dependent density-matrix renormalization-group and linear response theory, that such a superlattice modulation... [Phys. Rev. A 98, 033605] Published Fri Sep 14, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Cooling fermions in an optical lattice by adiabatic demagnetization (2018)
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    Publication Date: 2018-09-25
    Description: Author(s): Anthony E. Mirasola, Michael L. Wall, and Kaden R. A. Hazzard The Fermi-Hubbard model describes ultracold fermions in an optical lattice and exhibits antiferromagnetic long-ranged order below the Néel temperature. However, reaching this temperature in the laboratory has remained an elusive goal. In other atomic systems, such as trapped ions, low temperatures h... [Phys. Rev. A 98, 033607] Published Mon Sep 24, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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  • 99
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    Fluctuations and quantum self-bound droplets in a dipolar Bose-Bose mixture (2018)
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    Publication Date: 2018-09-29
    Description: Author(s): Abdelâali Boudjemâa We systematically investigate the properties of three-dimensional dipolar binary Bose mixture at low temperatures. A set of coupled self-consistent equations of motion are derived for the two condensates. In the homogeneous case, useful analytical formulas for the condensate depletion, the anomalous... [Phys. Rev. A 98, 033612] Published Fri Sep 28, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
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    Monitoring squeezed collective modes of a one-dimensional Bose gas after an interaction quench using density-ripple analysis (2018)
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    Publication Date: 2018-10-04
    Description: Author(s): Max Schemmer, Aisling Johnson, and Isabelle Bouchoule We investigate the out-of-equilibrium dynamics following a sudden quench of the interaction strength in a one-dimensional quasicondensate trapped at the surface of an atom chip. Within a linearized approximation, the system is described by independent collective modes and the quench squeezes the pha... [Phys. Rev. A 98, 043604] Published Wed Oct 03, 2018
    Keywords: Matter waves and collective properties of cold atoms and molecules
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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