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  • Aircraft Propulsion and Power  (11)
  • RESEARCH AND SUPPORT FACILITIES (AIR)  (4)
  • 1
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    Applications of the ram accelerator to hypervelocity aerothermodynamic testing (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A ram accelerator used as a hypervelocity launcher for large-scale aeroballistic range applications in hypersonics and aerodynamics research is presented. It is an in-bore ramjet device in which a projectile shaped like the centerbody of a supersonic ramjet is propelled down a stationary tube filled with a tailored combustible gas mixture. Ram accelerator operation has been demonstrated at 39 mm and 90 mm bores, supporting the proposition that this launcher concept can be scaled up to very large bore diameters of the order of 30-60 cm. It is concluded that high quality data obtained from the tube wall and projectile during the aceleration process itself are very useful for understanding aerothermodynamics of hypersonic flow in general, and for providing important CFD validation benchmarks.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 92-3949
    Format: text
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  • 2
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    Experiments on hypersonic ramjet propulsion cycles using a ram accelerator (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Work on hypersonic propulsion research using a ram accelerator is presented. Several different ram accelerator propulsive cycles have been experimentally demonstrated over the Mach number range of 3 to 8.5. The subsonic, thermally choked combustion mode has accelerated projectiles to near the Chapman-Jouguet (C-J) detonation velocity within many different propellant mixtures. In the transdetonative velocity regime (85 to 115 percent of C-J speed), projectiles have established a propulsive cycle which allows them to transition smoothly from subdetonative to superdetonative velocities. Luminosity data indicate that the combustion process moves forward onto the projectile body as it approaches the C-J speed. In the superdetonative velocity range, the projectiles accelerate while always traveling faster than the C-J velocity. Ram accelerator projectiles operating continuously through these velocity regimes generate distinctive hypersonic phenomena which can be studied very effectively in the laboratory. These results would be very useful for validating sophisticated CFD computer codes and in collecting engineering data for potential airbreathing hypersonic propulsive systems.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AIAA PAPER 91-2489
    Format: text
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  • 3
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    Conceptual Design of a Supersonic Business Jet Propulsion System (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA's Ultra-Efficient Engine Technology Program (UEETP) is developing a suite of technology to enhance the performance of future aircraft propulsion systems. Areas of focus for this suite of technology include: Highly Loaded Turbomachinery, Emissions Reduction, Materials and Structures, Controls, and Propulsion-Airframe Integration. The two major goals of the UEETP are emissions reduction of both landing and take-off nitrogen oxides (LTO-NO(x)) and mission carbon dioxide (CO2) through fuel burn reductions. The specific goals include a 70 percent reduction in the current LTO-NO(x) rule and an 8 percent reduction in mission CO2 emissions. In order to gain insight into the potential applications and benefits of these technologies on future aircraft, a set of representative flight vehicles was selected for systems level conceptual studies. The Supersonic Business Jet (SBJ) is one of these vehicles. The particular SBJ considered in this study has a capacity of 6 passengers, cruise Mach Number of 2.0, and a range of 4,000 nautical miles. Without the current existence of an SBJ the study of this vehicle requires a two-phased approach. Initially, a hypothetical baseline SBJ is designed which utilizes only current state of the art technology. Finally, an advanced SBJ propulsion system is designed and optimized which incorporates the advanced technologies under development within the UEETP. System benefits are then evaluated and compared to the program and design requirements. Although the program goals are only concerned with LTO-NO(x) and CO2 emissions, it is acknowledged that additional concerns for an SBJ include take-off noise, overland supersonic flight, and cruise NO(x) emissions at high altitudes. Propulsion system trade-offs in the conceptual design phase acknowledge these issues as well as the program goals. With the inclusion of UEETP technologies a propulsion system is designed which performs at 81% below the LTO-NO(x) rule, and reduces fuel burn by 23 percent compared to the current technology.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211797 , E-13492 , NAS 1.15:211797 , AIAA Paper 2002-3919 , 38th Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
    Format: application/pdf
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  • 4
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    Application of Pressure Sensitive Paint to Confined Flow at Mach Number 2.5 (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Pressure sensitive paint (PSP) is a novel technology that is being used frequently in external aerodynamics. For internal flows in narrow channels, and applications at elevated nonuniform temperatures, however, there are still unresolved problems that complicate the procedures for calibrating PSP signals. To address some of these problems, investigations were carried out in a narrow channel with supersonic flows of Mach 2.5. The first set of tests focused on the distribution of the wall pressure in the diverging section of the test channel downstream of the nozzle throat. The second set dealt with the distribution of wall static pressure due to the shock/wall interaction caused by a 25 deg. wedge in the constant Mach number part of the test section. In addition, the total temperature of the flow was varied to assess the effects of temperature on the PSP signal. Finally, contamination of the pressure field data, caused by internal reflection of the PSP signal in a narrow channel, was demonstrated. The local wall pressures were measured with static taps, and the wall pressure distributions were acquired by using PSP. The PSP results gave excellent qualitative impressions of the pressure field investigated. However, the quantitative results, specifically the accuracy of the PSP data in narrow channels, show that improvements need to be made in the calibration procedures, particularly for heated flows. In the cases investigated, the experimental error had a standard deviation of +/- 8.0% for the unheated flow, and +/- 16.0% for the heated flow, at an average pressure of 11 kpa.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-1998-107527 , E-10842 , NAS 1.15:107527 , AIAA Paper 97-3214 , Joint Propulsion Conference; Jul 06, 1997 - Jul 09, 1997; Seattle, WA; United States
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  • 5
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    An Assessment of Gas Foil Bearing Scalability and the Potential Benefits to Civilian Turbofan Engines (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Over the past several years the term oil-free turbomachinery has been used to describe a rotor support system for high speed turbomachinery that does not require oil for lubrication, damping, or cooling. The foundation technology for oil-free turbomachinery is the compliant foil bearing. This technology can replace the conventional rolling element bearings found in current engines. Two major benefits are realized with this technology. The primary benefit is the elimination of the oil lubrication system, accessory gearbox, tower shaft, and one turbine frame. These components account for 8 to 13 percent of the turbofan engine weight. The second benefit that compliant foil bearings offer to turbofan engines is the capability to operate at higher rotational speeds and shaft diameters. While traditional rolling element bearings have diminished life, reliability, and load capacity with increasing speeds, the foil bearing has a load capacity proportional to speed. The traditional applications for foil bearings have been in small, lightweight machines. However, recent advancements in the design and manufacturing of foil bearings have increased their potential size. An analysis, grounded in experimentally proven operation, is performed to assess the scalability of the modern foil bearing. This analysis was coupled to the requirements of civilian turbofan engines. The application of the foil bearing to larger, high bypass ratio engines nominally at the 120 kN (approx.25000 lb) thrust class has been examined. The application of this advanced technology to this system was found to reduce mission fuel burn by 3.05 percent.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2010-216732 , GT2010-22118 , E-17309 , Turbo Expo 2010; Jun 14, 2010 - Jun 18, 2010; Glasgow, Scotland; United Kingdom
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  • 6
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    Mixed composition materials suitable for vacuum web sputter coating (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Ion beam sputter deposition techniques were used to investigate simultaneous sputter etching of two component targets so as to produce mixed composition films. Although sputter deposition has been largely confined to metals and metal oxides, at least one polymeric material, poly-tetra-fluorethylene, has been demonstrated to produce sputtered fragments which repolymerize upon deposition to produce a highly cross-linked fluoropolymer resembling that of the parent target Fluoropolymer-filled silicon dioxide and fluoropolymer-filled aluminum oxide coatings have been deposited by means of ion beam sputter coat deposition resulting in films having material properties suitable for aerospace and commercial applications. The addition of fluoropolymer to silicon dioxide films was found to increase the hydrophobicity of the resulting mixed films; however, adding fluoropolymer to aluminum oxide films resulted in a reduction in hydrophobicity, thought to be caused by aluminum fluoride formation.
    Keywords: Aircraft Propulsion and Power
    Type: NASA-TM-107264 , NAS 1.15:107264 , E-10329 , Annual Technical Conference; May 08, 1996 - May 10, 1996; Philadelphia, PA; United States
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  • 7
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    Preliminary Analysis for an Optimized Oil-Free Rotorcraft Engine Concept (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Recent developments in gas foil bearing technology have led to numerous advanced high-speed rotating system concepts, many of which have become either commercial products or experimental test articles. Examples include Oil-Free microturbines, motors, generators and turbochargers. The driving forces for integrating gas foil bearings into these high-speed systems are the benefits promised by removing the oil lubrication system. Elimination of the oil system leads to reduced emissions, increased reliability, and decreased maintenance costs. Another benefit is reduced power plant weight. For rotorcraft applications, this would be a major advantage, as every pound removed from the propulsion system results in a payload benefit. Implementing foil gas bearings throughout a rotorcraft gas turbine engine is an important long-term goal that requires overcoming numerous technological hurdles. Adequate thrust bearing load capacity and potentially large gearbox applied radial loads are among them. However, by replacing the turbine end, or hot section, rolling element bearing with a gas foil bearing many of the above benefits can be realized. To this end, engine manufacturers are beginning to explore the possibilities of hot section gas foil bearings in propulsion engines. This paper presents a logical follow-on activity by analyzing a conceptual rotorcraft engine to determine the feasibility of a foil bearing supported core. Using a combination of rotordynamic analyses and a load capacity model, it is shown to be reasonable to consider a gas foil bearing core section.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215064 , ARL-TR-4398 , E-16290 , American Helicopter Society 63rd Annual Forum and Technology Display; May 01, 2007 - May 03, 2007; Virginia Beach, VA; United States
    Format: application/pdf
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  • 8
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    Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A methodology for the design and construction of simple foil thrust bearings intended for parametric performance testing and low marginal costs is presented. Features drawn from a review of the open literature are discussed as they relate to bearing performance. The design of fixtures and tooling required to fabricate foil thrust bearings is presented, using conventional machining processes where possible. A prototype bearing with dimensions drawn from the literature is constructed, with all fabrication steps described. A load-deflection curve for the bearing is presented to illustrate structural stiffness characteristics. Start-top cycles are performed on the bearing at a temperature of 425 C to demonstrate early-life wear patterns. A test of bearing load capacity demonstrates useful performance when compared with data obtained from the open literature.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2008-215062 , GT2008-50377 , E-16284 , Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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  • 9
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    Oil-Free Rotor Support Technologies for an Optimized Helicopter Propulsion System (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An optimized rotorcraft propulsion system incorporating a foil air bearing supported Oil-Free engine coupled to a high power density gearbox using high viscosity gear oil is explored. Foil air bearings have adequate load capacity and temperature capability for the highspeed gas generator shaft of a rotorcraft engine. Managing the axial loads of the power turbine shaft (low speed spool) will likely require thrust load support from the gearbox through a suitable coupling or other design. Employing specially formulated, high viscosity gear oil for the transmission can yield significant improvements (approx. 2X) in allowable gear loading. Though a completely new propulsion system design is needed to implement such a system, improved performance is possible.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2007-214845 , ISABE-2007-1145 , E-15976-1 , 18th ISABE Conference (ISABE 2007); Sep 02, 2007 - Sep 07, 2007; Beijing; China
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  • 10
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    System Analysis and Performance Benefits of an Optimized Rotorcraft Propulsion System (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The propulsion system of rotorcraft vehicles is the most critical system to the vehicle in terms of safety and performance. The propulsion system must provide both vertical lift and forward flight propulsion during the entire mission. Whereas propulsion is a critical element for all flight vehicles, it is particularly critical for rotorcraft due to their limited safe, un-powered landing capability. This unparalleled reliability requirement has led rotorcraft power plants down a certain evolutionary path in which the system looks and performs quite similarly to those of the 1960 s. By and large the advancements in rotorcraft propulsion have come in terms of safety and reliability and not in terms of performance. The concept of the optimized propulsion system is a means by which both reliability and performance can be improved for rotorcraft vehicles. The optimized rotorcraft propulsion system which couples an oil-free turboshaft engine to a highly loaded gearbox that provides axial load support for the power turbine can be designed with current laboratory proven technology. Such a system can provide up to 60% weight reduction of the propulsion system of rotorcraft vehicles. Several technical challenges are apparent at the conceptual design level and should be addressed with current research.
    Keywords: Aircraft Propulsion and Power
    Type: Fundamental Aeromautics Program Technical Forum; Oct 30, 2007 - Nov 01, 2007; New Orleans, LA; United States
    Format: application/pdf
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