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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Hybrid fuel cell/diesel generation total energy system, part 2

Meeting the Goldstone Deep Space Communications Complex (DGSCC) electrical and thermal requirements with the existing system was compared with using fuel cells. Fuel cell technology selection was based on a 1985 time frame for installation. The most cost-effective fuel feedstock for fuel cell application was identified. Fuels considered included diesel oil, natural gas, methanol and coal. These fuel feedstocks were considered not only on the cost and efficiency of the fuel conversion process, but also on complexity and integration of the fuel processor on system operation and thermal energy availability. After a review of fuel processor technology, catalytic steam reformer technology was selected based on the ease of integration and the economics of hydrogen production. The phosphoric acid fuel cell was selected for application at the GDSCC due to its commercial readiness for near term application. Fuel cell systems were analyzed for both natural gas and methanol feedstock. The subsequent economic analysis indicated that a natural gas fueled system was the most cost effective of the cases analyzed.

Blazek, C. F.↗
NASA NTRS1983

Stirling engine application study

A range of potential applications for Stirling engines in the power range from 0.5 to 5000 hp is surveyed. Over one hundred such engine applications are grouped into a small number of classes (10), with the application in each class having a high degree of commonality in technical performance and cost requirements. A review of conventional engines (usually spark ignition or Diesel) was then undertaken to determine the degree to which commercial engine practice now serves the needs of the application classes and to detemine the nature of the competition faced by a new engine system. In each application class the Stirling engine was compared to the conventional engines, assuming that objectives of ongoing Stirling engine development programs are met. This ranking process indicated that Stirling engines showed potential for use in all application classes except very light duty applications (lawn mowers, etc.). However, this potential is contingent on demonstrating much greater operating life and reliability than has been demonstrated to date by developmental Stirling engine systems. This implies that future program initiatives in developing Stirling engine systems should give more emphasis to life and reliability issues than has been the case in ongoing programs.

Teagan, W. P.↗
NASA NTRS1983

An overview of general aviation propulsion research programs at NASA Lewis Research Center

The review covers near-term improvements for current-type piston engines, as well as studies and limited corroborative research on several advanced g/a engine concepts, including diesels, small turboprops and both piston and rotary stratified-charge engines. Also described is basic combustion research, cycle modeling and diagnostic instrumentation work that is required to make new engines a reality.

Willis, E. A.↗
NASA NTRS1983

Autoignition in a premixing-prevaporizing fuel duct using 3 different fuel injection systems at inlet air temperatures to 1250 K

Conditions were determined in a continuous-flow, premixing-prevaporizing duct at which autoignition occurred. Test conditions were representative of an advanced, regenerative-cycle, automotive gas turbine. The test conditions inlet air temperatures from 600 to 1250 K (a vitiated preheater was used), pressures from 170 to 600 kPa, air velocities of 10 to 30 m/sec, equivalence ratios from 0.3 to 1.0, mixing lengths from 10 to 60 cm, and residence times of 2 to 100 ms. The fuel was diesel number 2. The duct was insulated and had an inside diameter of 12 cm. Three different fuel injection systems were used: One was a single simplex pressure atomizer, and the other two were multiple-source injectors. The data obtained with the simplex and one of the multiple-source injectors agreed satisfactorily with the references and correlated with an Arrenhius expression. The data obtained with the other multiple source injector, which used multiple cones to improve the fuel-air distribution, did not correlate well with residence time.

Tacina, R. R.↗
NASA NTRS1983

Demonstration and evaluation of gas turbine transit buses

The Gas Turbine Transit Bus Demonstration Program was designed to demonstrate and evaluate the operation of gas turbine engines in transit coaches in revenue service compared with diesel powered coaches. The main objective of the program was to accelerate development and commercialization of automotive gas turbines. The benefits from the installation of this engine in a transit coach were expected to be reduced weight, cleaner exhaust emissions, lower noise levels, reduced engine vibration and maintenance requirements, improved reliability and vehicle performance, greater engine braking capability, and superior cold weather starting. Four RTS-II advanced design transit coaches were converted to gas turbine power using engines and transmissions. Development, acceptance, performance and systems tests were performed on the coaches prior to the revenue service demonstration.

Source record↗
NASA NTRS1983

Multi-Fuel Rotary Engine for General Aviation Aircraft

Design studies, conducted for NASA, of Advanced Multi-fuel General Aviation and Commuter Aircraft Rotary Stratified Charge Engines are summarized. Conceptual design studies of an advanced engine sized to provide 186/250 shaft KW/HP under cruise conditions at 7620/25,000 m/ft. altitude were performed. Relevant engine development background covering both prior and recent engine test results of the direct injected unthrottled rotary engine technology, including the capability to interchangeably operate on gasoline, diesel fuel, kerosene, or aviation jet fuel, are presented and related to growth predictions. Aircraft studies, using these resultant growth engines, define anticipated system effects of the performance and power density improvements for both single engine and twin engine airplanes. The calculated results indicate superior system performance and 30 to 35% fuel economy improvement for the Rotary-engine airplanes as compared to equivalent airframe concept designs with current baseline engines. The research and technology activities required to attain the projected engine performance levels are also discussed.

Jones, C.↗
NASA NTRS1982

Performance improvements of single-engine business airplanes by the integration of advanced technologies

An assessment is presented of the performance gains and economic impact of the integration in general aviation aircraft of advanced technologies, relating to such aspects of design as propulsion, natural laminar flow, lift augmentation, unconventional configurations, and advanced aluminum and composite structures. All considerations are with reference to a baseline mission of 1300 nm range and 300-knot cruise speed with a 1300-lb payload, and a baseline aircraft with a 40 lb/sq ft wing loading and an aspect ratio of 8. Extensive analytical results are presented from the NASA-sponsored General Aviation Synthesis Program. Attention is given to the relative performance gains to be expected from the single-engined baseline aircraft's use of a low cost general aviation turbine engine, a spark-ignited reciprocating engine, a diesel engine, and a Wankel rotary engine.

Kohlman, D. L.↗
NASA NTRS1983

Downsizing assessment of automotive Stirling engines

A 67 kW (90 hp) Stirling engine design, sized for use in a 1984 1440 kg (3170 lb) automobile was the focal point for developing automotive Stirling engine technology. Since recent trends are towards lighter vehicles, an assessment was made of the applicability of the Stirling technology being developed for smaller, lower power engines. Using both the Philips scaling laws and a Lewis Research Center (Lewis) Stirling engine performance code, dimensional and performance characteristics were determined for a 26 kW (35 hp) and a 37 kW (50 hp) engine for use in a nominal 907 kg (2000 lb) vehicle. Key engine elements were sized and stressed and mechanical layouts were made to ensure mechanical fit and integrity of the engines. Fuel economy estimates indicated that the Stirling engine would maintain a 30 to 45 percent fuel economy advantage comparable spark ignition and diesel powered vehicles in the 1984 period.

Knoll, R. H.↗
NASA NTRS1983

Evaluation of CO2 and CO dopants in hydrogen to reduce hydrogen permeation in the Stirling engine heater head tube alloy CG-27

Tubes of CG-27 alloy, filled with hydrogen doped with various amounts of carbon dioxide and carbon monoxide, were heated in a diesel fuel fired Stirling engine simulator materials test rig for 100 hours at 820 C and at a gas pressure of 15 MPa to determine the effectiveness of the dopants in reducing hydrogen permeation through the hot tube wall. This was done for clean as-heat treated tubes and also for tubes that had previously been exposed for 100 hours to hydrogen doped with 1.0 volume percent carbon dioxide to determine if the lower levels of dopant could maintain a low hydrogen permeation through the hot tube wall. Carbon dioxide, as a dopant in hydrogen, was most effective in reducing hydrogen permeation through clean tubes and in maintaining low hydrogen permeation after prior exposure to 1.0 volume percent carbon dioxide. Only the lowest level of carbon dioxide (0.05 volume percent) was not as effective in the clean or prior exposed tubes. Carbon monoxide as a dopant in hydrogen was less effective than carbon dioxide at a given concentration level. Of the four dopant levels studied; 1.0, 0.5, 0.2, and 0.05 volume percent carbon monoxide, only the 1.0 and 0.5 volume percent were effective in reducing and maintaining low hydrogen permeation through the CG-27.

Misencik, J. A.↗
NASA NTRS1980

Apparatus and method for destructive removal of particles contained in flowing fluid

An apparatus and method for destructively removing particles from a flowing gas containing the particles is described. In the specific embodiments disclosed the apparatus is adapted to remove carbon particles from diesel engine exhaust products. The exhaust products are directed to a predetermined location where they are rapidly vaporized and combine with oxygen in the exhaust products to form carbon dioxide. Vaporization in one embodiment is effected by a discharge grid located within an exhaust conduit, the grid being chosen so that alternate conductors defining the grid are spaced apart a distance approximately 125 times the mean diameter of the particles to be removed. A voltage differential of approximately 690 volts is applied across adjacent conductors.

Yang, L. C.↗
NASA NTRS1983

New applications for phosphoric acid fuel cells

New applications for phosphoric acid fuel cells were identified and evaluated. Candidates considered included all possibilities except grid connected electric utility applications, on site total energy systems, industrial cogeneration, opportunistic use of waste hydrogen, space and military applications, and applications smaller than 10 kW. Applications identified were screened, with the most promising subjected to technical and economic evaluation using a fuel cell and conventional power system data base developed in the study. The most promising applications appear to be the underground mine locomotive and the railroad locomotive. Also interesting are power for robotic submersibles and Arctic villages. The mine locomotive is particularly attractive since it is expected that the fuel cell could command a very high price and still be competitive with the conventionally used battery system. The railroad locomotive's attractiveness results from the (smaller) premium price which the fuel cell could command over the conventional diesel electric system based on its superior fuel efficiency, and on the large size of this market and the accompanying opportunities for manufacturing economy.

Stickles, R. P.↗
NASA NTRS1984

Measurements in liquid fuel sprays

Techniques for studying the events directly preceding combustion in the liquid fuel sprays are being used to provide information as a function of space and time on droplet size, shape, number density, position, angle of flight and velocity. Spray chambers were designed and constructed for: (1) air-assist liquid fuel research sprays; (2) high pressure and temperature chamber for pulsed diesel fuel sprays; and (3) coal-water slurry sprays. Recent results utilizing photography, cinematography, and calibration of the Malvern particle sizer are reported. Systems for simultaneous measurement of velocity and particle size distributions using laser Doppler anemometry interferometry and the application of holography in liquid fuel sprays are being calibrated.

Chigier, N.↗
NASA NTRS1984

Fuel property effects on USAF gas turbine engine combustors and afterburners

Since the early 1970s, the cost and availability of aircraft fuel have changed drastically. These problems prompted a program to evaluate the effects of broadened specification fuels on current and future aircraft engine combustors employed by the USAF. Phase 1 of this program was to test a set of fuels having a broad range of chemical and physical properties in a select group of gas turbine engine combustors currently in use by the USAF. The fuels ranged from JP4 to Diesel Fuel number two (DF2) with hydrogen content ranging from 14.5 percent down to 12 percent by weight, density ranging from 752 kg/sq m to 837 kg/sq m, and viscosity ranging from 0.830 sq mm/s to 3.245 sq mm/s. In addition, there was a broad range of aromatic content and physical properties attained by using Gulf Mineral Seal Oil, Xylene Bottoms, and 2040 Solvent as blending agents in JP4, JP5, JP8, and DF2. The objective of Phase 2 was to develop simple correlations and models of fuel effects on combustor performance and durability. The major variables of concern were fuel chemical and physical properties, combustor design factors, and combustor operating conditions.

Reeves, C. M.↗
NASA NTRS1984

An overview of NASA intermittent combustion engine research

This paper overviews the current program, whose objective is to establish the generic technology base for advanced aircraft I.C. engines of the early 1990's and beyond. The major emphasis of this paper is on development of the past two years. Past studies and ongoing confirmatory experimental efforts are reviewed, which show unexpectly high potential when modern aerospace technologies are applied to inherently compact and balanced I.C. engine configurations. Currently, the program is focussed on two engine concepts the stratified-charge, multi-fuel rotary, and the lightweight two-stroke diesel. A review is given of contracted and planned high performance one-rotor and one-cylinder test engine work addressing several levels of technology. Also reviewed are basic supporting efforts, e.g., the development and experimental validation of computerized airflow and combustion process models, being performed in-house at Lewis Research Center and by university grants.

Willis, E. A.↗
NASA NTRS1984

Non-steady State Effects in EHL

A number of lubricated machine elements are subjected to cyclic variations of load and speed, particularly in reciprocating machinery. It is well known that squeeze-film action plays an important role in preserving satisfactory lubricating films in many cases in which the entraining velocities fall to zero during each cycle, as in the reciprocating seal and synovial joints. The essential features of combined 'entraining' and 'normal' motion are described for both hydrodynamic and elastohydrodynamic conditions. It is shown that very small squeeze-film velocities (W), or order (h(sub o)/l)U, can lead to substantial hydrodynamic action. A brief review of previous studies of squeeze-film lubrication between spheres or cylinders and a plane is followed by reference to a recent analysis of ankle joint lubrication. It is then shown that elastohydrodynamic lubrication might be encountered in the conjunction between a piston ring and cylinder liner and that in such cases combined entraining and squeeze-film action is important. Analysis of a 2-stroke Diesel engine shows that variations in squeeze-film velocity throughout the conjunction, associated with time rates of change of elastic deformation, must be considered in a full elastohydrodynamic lubrication analysis.

Duncan Dowson↗
NASA NTRS1984

Status and New Directions for Solid Lubricant Coatings and Composite Materials

At one time, solid lubricants were used almost entirely in aerospace applications. Today there is a pronounced trend to use them over a much broader range of applications. For example, self-lubricating polymer-based composites have displaced traditional oil-lubricated, metallic composites for many journal bearings and thrust, washers in applications as diverse as earthmoving machinery and snow blowers to aircraft applications. For moderate temperatures below 200° C, glass filament-wound epoxy bearings with PTFE lubricating liners are useful; for temperatures up to 350° C, graphite fiber reinforced polyimide bearing materials are finding applications. Molybdenum disulfide, graphite, and PTFE are the most widely known and used solid lubricants, and there is increasing interest in the relatively new solid lubricant graphite fluoride. Advanced technology engines such as the adiabatic diesel and the small, efficient gas turbine have severe lubrication and wear problems at temperatures beyond the capabilities of any of these lubricants. Here, self-lubricating ceramics and inorganic composites for use at I000° C or higher are of interest. However, perhaps the most significant new direction for solid lubricant coatings and self-lubricating composites is their steadily increasing use in dry bearings for large volume, moderate temperature applications. This can be attributed to their simplicity of use (no supporting lubricant system needed), light weight, convenience, and general cost effectiveness.

Harold E Sliney↗
NASA NTRS1984

Application of selected advanced technologies to high performance, single-engine, business airplanes

Improvements in performance and fuel efficiency are evaluated for five new configurations of a six place, single turboprop, business airplane derived from a conventional, aluminum construction baseline aircraft. Results show the greatest performance gains for enhancements in natural laminar flow. A conceptual diesel engine provides greater fuel efficiency but reduced performance. Less significant effects are produced by the utilization of composite materials construction or by reconfiguration from tractor to pusher propeller installation.

Domack, C. S.↗
NASA NTRS1984

Oxidation and corrosion resistance of candidate Stirling engine heater-head-tube alloys

Sixteen candidate iron base Stirling engine heater head tube alloys are evaluated in a diesel fuel fired simulator materials test rig to determine their oxidation and corrosion resistance. Sheet specimens are tested at 820 C for 3500 hr in 5 hr heating cycles. Specific weight change data and an attack parameter are used to categorize the alloys into four groups; 10 alloys show excellent for good oxidation and corrosion resistance and six alloys exhibit poor or catastrophic resistance. Metallographic, X-ray, and electron microprobe analyses aid in further characterizing the oxidation and corrosion behavior of the alloys. Alloy compositions, expecially the reactive elements aluminum, titanium, and chromium, play a major role in the excellent oxidation and corrosion behavior of the alloys. The best oxidation resistance is associated with the formation of an iron nickel aluminum outer oxide scale, an intermediate oxide scale rich in chromium and titanium, and an aluminum outer oxide scale adjacent to the metallic substrate, which exhibits a zone of internal oxidation of aluminum and to some extent titanium.

Stephens, J. R.↗