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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Aircraft symmetric flight optimization

Review of the development of gradient techniques and their application to aircraft optimal performance computations in the vertical plane of flight. Results obtained using the method of gradients are presented for attitude- and throttle-control programs which extremize the fuel, range, and time performance indices subject to various trajectory and control constraints, including boundedness of engine throttle control. A penalty function treatment of state inequality constraints which generally appear in aircraft performance problems is outlined. Numerical results for maximum-range, minimum-fuel, and minimum-time climb paths for a hypothetical supersonic turbojet interceptor are presented and discussed. In addition, minimum-fuel climb paths subject to various levels of ground overpressure intensity constraint are indicated for a representative supersonic transport. A variant of the Gel'fand-Tsetlin 'method of ravines' is reviewed, and two possibilities for further development of continuous gradient processes are cited - namely, a projection version of conjugate gradients and a curvilinear search.

Falco, M.↗
NASA NTRS1982

Wind tunnel tests of a zero length, slotted-lip engine air inlet for a fixed nacelle V/STOL aircraft

Zero length, slotted lip inlet performance and associated fan blade stresses were determined during model tests using a 20 inch diameter fan simulator in the NASA-LeRC 9 by 15 foot low speed wind tunnel. The model configuration variables consisted of inlet contraction ratio, slot width, circumferential extent of slot fillers, and length of a constant area section between the inlet throat and fan face. The inlet performance was dependent on slot gap width and relatively independent of inlet throat/fan face spacer length and slot flow blockage created by 90 degree slot fillers. Optimum performance was obtained at a slot gap width of 0.36 inch. The zero length, slotted lip inlet satisfied all critical low speed inlet operating requirements for fixed horizontal nacelles subsonic V/STOL aircraft.

Woollett, R. R.↗
NASA NTRS1992

Liquid lubricants for advanced aircraft engines

An overview of liquid lubricants for use in current and projected high performance turbojet engines is discussed. Chemical and physical properties are reviewed with special emphasis placed on the oxidation and thermal stability requirements imposed upon the lubrication system. A brief history is given of the development of turbine engine lubricants which led to the present day synthetic oils with their inherent modification advantages. The status and state of development of some eleven candidate classes of fluids for use in advanced turbine engines are discussed. Published examples of fundamental studies to obtain a better understanding of the chemistry involved in fluid degradation are reviewed. Alternatives to high temperature fluid development are described. The importance of continuing work on improving current high temperature lubricant candidates and encouraging development of new and improved fluid base stocks are discussed.

Loomis, William R.↗
NASA NTRS1993

Liquid lubricants for advanced aircraft engines

An overview of liquid lubricants for use in current and projected high performance turbojet engines is discussed. Chemical and physical properties are reviewed with special emphasis placed on the oxidation and thermal stability requirements imposed upon the lubrication system. A brief history is given of the development of turbine engine lubricants which led to the present day synthetic oils with their inherent modification advantages. The status and state of development of some eleven candidate classes of fluids for use in advanced turbine engines are discussed. Published examples of fundamental studies to obtain a better understanding of the chemistry involved in fluid degradation are reviewed. Alternatives to high temperature fluid development are described. The importance of continuing work on improving current high temperature lubricant candidates and encouraging development of new and improved fluid base stocks are discussed.

Loomis, William R.↗
NASA NTRS1989

Study of high-speed civil transports

A systems study to identify the economic potential for a high-speed commercial transport (HSCT) has considered technology, market characteristics, airport infrastructure, and environmental issues. Market forecasts indicate a need for HSCT service in the 2000/2010 time frame conditioned on economic viability and environmental acceptability. Design requirements focused on a 300 passenger, 3 class service, and 6500 nautical mile range based on the accelerated growth of the Pacific region. Compatibility with existing airports was an assumed requirement. Mach numbers between 2 and 25 were examined in conjunction with the appropriate propulsion systems, fuels, structural materials, and thermal management systems. Aircraft productivity was a key parameter with aircraft worth, in comparison to aircraft price, being the airline-oriented figure of merit. Aircraft screening led to determination that Mach 3.2 (TSJF) would have superior characteristics to Mach 5.0 (LNG) and the recommendation that the next generation high-speed commercial transport aircraft use a kerosene fuel. The sensitivity of aircraft performance and economics to environmental constraints (e.g., sonic boom, engine emissions, and airport/community noise) was identified together with key technologies. In all, current technology is not adequate to produce viable HSCTs for the world marketplace. Technology advancements must be accomplished to meet environmental requirements (these requirements are as yet undetermined for sonic boom and engine emissions). High priority is assigned to aircraft gross weight reduction which benefits both economics and environmental aspects. Specific technology requirements are identified and national economic benefits are projected.

Source record↗
NASA NTRS1980

Small Transport Aircraft Technology /STAT/ Propulsion Study

The NASA Small Transport Aircraft Technology (STAT) Propulsion Study was established to identify technology requirements and define the research and development required for new commuter aircraft. Interim results of the studies defined mission and design characteristics for 30- and 50-passenger aircraft. Sensitivities were defined that relate changes in engine specific fuel consumption (SFC), weight, and cost (including maintenance) to changes in the aircraft direct operating cost (DOC), takeoff gross weight, and empty weight. A comparison of performance and economic characteristics is presented between aircraft powered by 1980 production engines and those powered by a 1990 advanced technology baseline engine.

Heldenbrand, R. W.↗
NASA NTRS2022

An Analysis of the Impact of Extreme Attitude Operation on a Turbofan Engine in a Regional Jet Aircraft

The objective of this work is to characterize the variability in engine performance at extreme attitudes, resulting from the use of different standard control variables, evaluated at different points in the engine’s lifecycle. This paper describes the procedure used to create a dynamic model of an aft-mounted jet engine on a T-tail regional jet aircraft. This model enables simulation of engine operation at extreme attitudes. The model was subsequently evaluated at various altitudes, Mach numbers, and power settings over a range of angles of attack and sideslip, and deterioration levels. Each case was simulated using both fan speed and engine pressure ratio as the engine control variable. The results show that the wing has a very large impact on the engine operation, overwhelming other sources of variation.

loss of control - inflight↗
NASA NTRS1977

A study of commuter aircraft design

This paper investigates the impact of configuration considerations, mission requirements, and performance constraints on conceptual commuter aircraft designs. Emphasis is placed on direct comparisons between turbofan and turboprop powered aircraft in the 10-30 passenger class. The analysis is accomplished using a computerized aircraft synthesis model that simulates the aircraft design and mission. The resulting conceptual aircraft are similar in size and performance regardless of engine type but the turboprop offers more mission flexibility

Galloway, T. L.↗
NASA NTRS1980

Some considerations of the performance of two honeycomb gas path seal material systems

A standard Hastelloy-X honeycomb material and a pack aluminide coated honeycomb material were evaluated as to their performance as labyrinth seal materials for aircraft gas turbine engines. Consideration from published literature was given to the fluid sealing characteristics of two honeycomb materials in labyrinth seal applications, and their rub characteristics, erosion resistance, and oxidation resistance were evaluated. The increased temperature potential of the coated honeycomb material compared to the uncoated standard could be achieved without compromising the honeycomb material's rub tolerance, although there was some penalty in terms of reduced erosion resistance.

Bill, R. C.↗
NASA NTRS1982

Advances in Turbine-Engine Technology

Status report describes major advances in high-temperature materials, coatings, and turbine-blade coating technology for aircraft turbine engines, which are keys to achieving improved performance.

Freche, J. C.↗
NASA NTRS1984

The NASA broad specification fuels combustion technology program at Pratt and Whitney

The technology required to accommodate the use of broadened properties fuels in commercial aircraft engine combustors with minimum impact on the emissions, performance, durability and engine operational characteristics is discussed. Emphasis was placed on defining the potential for reducing the fuel sensitivity of the reference combustion system through design refinements and the introduction of more advanced technology combustors. To this end the tests conducted included the evaluation of variations of three different combustor concepts representing progressively more advanced technology levels. It was demonstrated that reduced fuel hydrogen content has adverse impacts on current single stage combustors; the best opportunities for reducing the fuel sensitivity of these combustors are through improved fuel injectors and advanced liner cooling and structural concepts and that the advanced technology staged and variable geometry combustor concepts have inherent operational flexibility that can be exploited to accommodate changes in fuel composition. Also, advanced technology combustor concepts were evaluated. A variable geometry combustor capable of airflow modulation during operation and a new concept which is a further evolution of the Vorbix combustor are discussed.

Lohmann, R. P.↗
NASA NTRS1986

Development of a knowledge acquisition tool for an expert system flight status monitor

Two of the main issues in artificial intelligence today are knowledge acquisition dion and knowledge representation. The Dryden Flight Research Facility of NASA's Ames Research Center is presently involved in the design and implementation of an expert system flight status monitor that will provide expertise and knowledge to aid the flight systems engineer in monitoring today's advanced high-performance aircraft. The flight status monitor can be divided into two sections: the expert system itself and the knowledge acquisition tool. The knowledge acquisition tool, the means it uses to extract knowledge from the domain expert, and how that knowledge is represented for computer use is discussed. An actual aircraft system has been codified by this tool with great success. Future real-time use of the expert system has been facilitated by using the knowledge acquisition tool to easily generate a logically consistent and complete knowledge base.

Disbrow, J. D.↗
NASA NTRS1986

Development of a knowledge acquisition tool for an expert system flight status monitor

Two of the main issues in artificial intelligence today are knowledge acquisition and knowledge representation. The Dryden Flight Research Facility of NASA's Ames Research Center is presently involved in the design and implementation of an expert system flight status monitor that will provide expertise and knowledge to aid the flight systems engineer in monitoring today's advanced high-performance aircraft. The flight status monitor can be divided into two sections: the expert system itself and the knowledge acquisition tool. This paper discusses the knowledge acquisition tool, the means it uses to extract knowledge from the domain expert, and how that knowledge is represented for computer use. An actual aircraft system has been codified by this tool with great success. Future real-time use of the expert system has been facilitated by using the knowledge acquisition tool to easily generate a logically consistent and complete knowledge base.

Disbrow, J. D.↗
NASA NTRS1989

Cabin noise control ground tests for UHB aircraft

Measurement and analysis procedures for cabin noise control ground tests conducted on a DC-9 aircraft test section are presented along with a summary of test results. These tests were designed to analyze the effectiveness of selected noise control treatments in reducing passenger cabin noise on aircraft with aft-mounted, advanced turboprop engines. The performance of various structural and cabin sidewall treatments is assessed, based on measurements of the resulting interior noise levels and fuselage acceleration levels under simulated advanced turboprop excitation.

Simpson, Myles A.↗
NASA NTRS1990

Three-dimensional stress intensity factor analysis of a surface crack in a high-speed bearing

The boundary element method is applied to calculate the stress intensity factors of a surface crack in the rotating inner raceway of a high-speed roller bearing. The three-dimensional model consists of an axially stressed surface cracked plate subjected to a moving Hertzian contact loading. A multidomain formulation and singular crack-tip elements were employed to calculate the stress intensity factors accurately and efficiently for a wide range of configuration parameters. The results can provide the basis for crack growth calculations and fatigue life predictions of high-performance rolling element bearings that are used in aircraft engines.

Ballarini, Roberto↗
NASA NTRS2004

Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design

The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

Min, James B.↗
NASA NTRS2005

Advanced Turbulence Modeling Concepts

The ZCET program developed at NASA Glenn Research Center is to study hydrogen/air injection concepts for aircraft gas turbine engines that meet conventional gas turbine performance levels and provide low levels of harmful NOx emissions. A CFD study for ZCET program has been successfully carried out. It uses the most recently enhanced National combustion code (NCC) to perform CFD simulations for two configurations of hydrogen fuel injectors (GRC- and Sandia-injector). The results can be used to assist experimental studies to provide quick mixing, low emission and high performance fuel injector designs. The work started with the configuration of the single-hole injector. The computational models were taken from the experimental designs. For example, the GRC single-hole injector consists of one air tube (0.78 inches long and 0.265 inches in diameter) and two hydrogen tubes (0.3 inches long and 0.0226 inches in diameter opposed at 180 degree). The hydrogen tubes are located 0.3 inches upstream from the exit of the air element (the inlet location for the combustor). To do the simulation, the single-hole injector is connected to a combustor model (8.16 inches long and 0.5 inches in diameter). The inlet conditions for air and hydrogen elements are defined according to actual experimental designs. Two crossing jets of hydrogen/air are simulated in detail in the injector. The cold flow, reacting flow, flame temperature, combustor pressure and possible flashback phenomena are studied. Two grid resolutions of the numerical model have been adopted. The first computational grid contains 0.52 million elements, the second one contains over 1.3 million elements. The CFD results have shown only about 5% difference between the two grid resolutions. Therefore, the CFD result obtained from the model of 1.3-million grid resolution can be considered as a grid independent numerical solution. Turbulence models built in NCC are consolidated and well tested. They can handle both coarse and fine grids near the wall. They can model the effect of anisotropy of turbulent stresses and the effect of swirling. The chemical reactions of Magnusson model and ILDM method were both used in this study.

Shih, Tsan-Hsing↗