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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The use of heterodyne speckle photogrammetry to measure high-temperature strain distributions

Thermal and mechanical strains have been measured on samples of a common material used in jet engine burner liners, which were heated from room temperature to 870 C and cooled back to 220 C, in a laboratory furnace. The physical geometry of the sample surface was recorded to select temperatures by means of a set of twelve single-exposure specklegrams. Sequential pairs of specklegrams were compared in a heterodyne interferometer which allowed high-precision measurement of differential displacements. Good speckle correlation was observed between the first and last specklegrams also, which showed the durability of the surface microstructure, and permitted a check on accumulated errors. Agreement with calculated thermal expansion was to within a few hundred microstrain over a range of fourteen thousand.

Stetson, K. A.↗
NASA NTRS1983

NASA advanced low emissions combustor program

The purpose of this program is to conduct combustion tests on lean, premixed, and prevaporized (LPP) combustor concepts designed for use in commercial aircraft engines to attain improved performance, durability, and lower pollutant emissions levels relative to current technology combustor designs. Four full annular combustors were designed for the CF6-50 engine. These concepts utilize premixing of the fuel and air, variable geometry, and fuel staging to control the equivalence ratios of the burning zone. The testing is being conducted on these four full annular combustors over a wide range of operating conditions at pressures up to actual subsonic cruise (1.16 MPa). The test results for the most promising of these combustor concepts are reported in this paper.

Goyal, A.↗
NASA NTRS1984

Optical coatings formulations containing tetrafluoroethylene

Two optical reference coatings containing tetrafluorethylene have been formulated using silicone binders. One of the silicones used is an oligomer of methyl silanol supplied at 48 percent solids in a mixture of butanol and ethanol. The other silicone is a proprietory silicone tethered ethyl silicate based colloidal silica binder supplied at 22 and 36 percent solids in a mixture of low molecular weight aliphatic alcohols. The coatins are characterized by high durability and have an overall reflectance in the visible part of the spectrum of about 90 percent. The substrate preparation and application procedures are described.

Schutt, J. B.↗
NASA NTRS1983

New perspectives for advanced automobile diesel engines

Computer simulation results are presented for advanced automobile diesel engine performance. Four critical factors for performance enhancement were identified: (1) part load preheating and exhaust gas energy recovery, (2) fast heat release combustion process, (3) reduction in friction, and (4) air handling system efficiency. Four different technology levels were considered in the analysis. Simulation results are compared in terms of brake specific fuel consumption and vehicle fuel economy in km/liter (miles per gallon). Major critical performance sensitivity areas are: (1) combustion process, (2) expander and compressor efficiency, and (3) part load preheating and compound system. When compared to the state of the art direct injection, cooled, automobile diesel engine, the advanced adiabatic compound engine concept showed the unique potential of doubling the fuel economy. Other important performance criteria such as acceleration, emissions, reliability, durability and multifuel capability are comparable to or better than current passenger car diesel engines.

Tozzi, L.↗
NASA NTRS1984

New phosphorus-containing bisimide resins

Phosphorus-based flame retardants have been effectively used in a wide variety of polymeric materials. Such additives, however, may either influence the decomposition reaction in polymers or lack durability due to a tendency to be leached out by solvents. Attention is given to the synthesis, characterization, thermal stability and degradation mechanisms of bisimide resins, and an evaluation is conducted of the flammability and mechanical properties of graphite cloth-reinforced laminates fabricated from one of the six phosphorus-containing bisimide resins considered.

Varma, I. K.↗
NASA NTRS1982

A technology data base for the design of 500 to 5000-lb thrust class liquid rocket engines utilizing hydrogen and oxygen as propellants

This paper presents an overview of the results of experimental evaluations of candidate designs for igniters, injectors, and propellant-cooled thrust chambers applicable to restartable high-performance, high-reliability upper-stage engines and to pulsing-type reaction control engines (RCE). Injection element types best suited for liquid, gas, and liquid/gas phase propellant supply are identified. The resulting interactions between element type, combustion efficiency, and chamber wall heating are compared. The distinction between thrust chamber design requirements for upper stage vs RCE applications as measured by cycle life requirements is translated into design configurations consisting of all-film-cooled, all-regeneratively-cooled, and composites of the two cooling approaches. The validity of the design approaches is confirmed by data from engine durability testing involving over 90,000 starts and 9,000 thermal cycles on RCE-type designs and multiple long-duration burns (up to 2,000 sec) on regeneratively cooled upper-stage designs.

Schoenman, L.↗
NASA NTRS1983

Surface analysis of grapite fiber reinforced polyimide composites. I

The results of experimental analyses of the effects of pretreatment on bonding between composite materials are reported. The materials comprised graphite fibers in a polyimide matrix. The surfaces were bonded as-received or subjected to grit blasting, bead blasting, hand sanding, washes with ethanolic KOH, NH2NH2-H2O or H2SO4 + 0.30 H2O2 or flashblasting. SEM and X-ray photoelectron spectroscopy revealed fluorine contents in the as-received samples. Contact angles were determined by means of five different liquids with various surface tensions. The flashblast technique removed all fluorine from the samples. Low critical surface tensions were found in the composite surfaces with high fluorine concentrations. The surface scanning techniques are concluded to be useful for studying factors influencing the strength and durability of adhesively bonded composites.

Messick, D. L.↗
NASA NTRS1983

NASA's role in aeronautical research

Past and current research in the aeronautical field conducted by NASA is reviewed. The first national center for aeronautical research, the Langley Memorial Aeronautical Laboratory, was established in 1917 by the then formed National Advisory Committee for Aeronautics (NACA). Two other research centers established later by NACA (Lewis and Ames) were staffed with research cadres from Langley. These three research centers formed the nucleus of NASA when it was established in 1958. Studies conducted today by NASA's research centers include: a concept for commuter-style aircraft, turbofan engines for military supersonic fighter aircraft, strength and durability of man-made fiber materials, and maneuverability problems in high speed aircraft. In addition, at Ames, research is being conducted on short-haul aviation, and short and vertical takeoff while at Lewis studies concentrate on propulsion system and engines. At Langley the emphasis is on basic research, stressing aircraft structure improvements, stall avoidance and noise abatement. Finally, the importance of NASA's educational program is discussed.

Parker, M.↗
NASA NTRS1984

Ceramic-coated metals can survive contact with hot working fluid

Thermal barrier coatings (TBCs) have been developed as a means of protecting turbine blades and other engine hot section components whose surfaces are exposed to the most extreme operating conditions. By adding a thin, insulating ceramic oxide layer to an air-cooled turbine blade, the difference between the gas temperature and the metal temperature is further increased as a function of ceramic coating thickness, heat flux, and oxide thermal conductivity. An 0.04-cm thick ceramic layer can typically yield a 100-300 C temperature drop. Of the various techniques available for the deposition of thermal barrier coatings, the most common is that of plasma spraying. Significant improvements have been made in TBC durability through the use of bond coat compositions with increased oxidation resistance.

Levine, S. R.↗
NASA NTRS1985

Airborne Cloud Detector

Bonded to aircraft skin, it facilitates cloud avoidance. Airborne cloud detector consists of three major components: Aluminum patch durably bonded to aircraft skin, surge arrester, and dual-sensitivity charge-rate amplifier. Operation based on fact that aircraft surfaces become charged when ice or water particles strike them. Using increased gain sensitivities, cloudparticle detector reliable, noise-free, low-cost, high-sensitivity indicator of type of clouds that cause most problems for LFC aircraft at cruise altitude.

Campbell, R. E.↗
NASA NTRS1986

Plasma-Sprayed Coatings on Porous Surfaces

Need for combining benefits of duplex thermal-barrier coatings with film cooling on gas-turbine vanes and blades stimulated development of improved method for plasma spraying these coatings. Method reduces blocking of holes by plasma-sprayed material and at same time reduces base-metal oxidation during coating operation. Features provide potential for increased engine efficiency and power, reduced fuel consumption, use of less costly materials or construction procedures, and extended life and durability.

Leibert, C. H.↗
NASA NTRS1982

Turbine Engine Hot Section Technology (HOST)

Research and plans concerning aircraft gas turbine engine hot section durability problems were discussed. Under the topics of structural analysis, fatigue and fracture, surface protective coatings, combustion, turbine heat transfer, and instrumentation specific points addressed were the thermal and fluid environment around liners, blades, and vanes, material coatings, constitutive behavior, stress-strain response, and life prediction methods for the three components.

Source record↗
NASA NTRS1984

Composite Structural Materials

The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

Ansell, G. S.↗
NASA NTRS1982

Design, ancillary testing, analysis and fabrication data for the advanced composite stabilizer for Boeing 737 aircraft, volume 2

Results of tests conducted to demonstrate that composite structures save weight, possess long term durability, and can be fabricated at costs competitive with conventional metal structures are presented with focus on the use of graphite-epoxy in the design of a stabilizer for the Boeing 737 aircraft. Component definition, materials evaluation, material design properties, and structural elements tests are discussed. Fabrication development, as well as structural repair and inspection are also examined.

Aniversario, R. B.↗
NASA NTRS1984

Laboratory Investigations

The primary objectives were to examine the site-specific physical, chemical, and biological factors that impact construction, durability and performance of the proposed 5-MW (sub e) solar pond system at the Salton Sea. The interactions of the water, salt, and soil of the site and on material compatibility were examined. Potential interactions of the water/brine and soil are particularly important because the pond will utilize the naturally occurring clays as a bottom seal. Although there is a considerable and growing solar pond literature, little written information deals with the important site-specific investigations of water, salt, and soil. Therefore, technical effort was directed toward identifying the factors that should be investigated and determining methods of investigation. As a result, a by-product was the development of an approach for site-specific investigations and some specific methodologies. This development should continue in order to establish a generic approach for evaluating the suitability of any site for the construction of large-scale solar ponds.

Source record↗
NASA NTRS1985

Experimental test program for evaluation of solid lubricant coating as applied to compliant foil gas bearings to 315 deg C

An experimental apparatus and test procedure was developed to compare the performance of two solid lubricant coatings for air lubricated compliant foil gas bearings in the temperature range of 25 to 315 C. Polyimide bonded additive (SBGC) were tested extensively for durability and frictional characteristics. A partial arc bearing constructed of Inconel X-750 was coated on the bore with one of these coatings. The foil was subjected to repeated start/stop cycles. Performance comparisons reveal that although both coatings survive thousands of start/stop cycles, only the PBGF coated bearing achieves the specified 9000 start/stops. There is enough wear on the SBGC coated bearing to warrant termination of the test prior to 9000 start/stop cycles due to coating failure. The frictional characteristics of the PBGF are better at the elevated temperatures than at lower temperatures; a marked increase in sliding friction occurs as the temperature decreases. The SBGC maintains relatively constant frictional characteristics independent of operating temperature.

Wagner, R. C.↗
NASA NTRS1984

High frequency plasma generator for ion thrusters

The results of a program to experimentally develop two new types of plasma generators for 30 cm electrostatic argon ion thrusters are presented. The two plasma generating methods selected for this study were by radio frequency induction (RFI), operating at an input power frequency of 1 MHz, and by electron cyclotron heating (ECH) at an operating frequency of 5.0 GHz. Both of these generators utilize multiline cusp permanent magnet configurations for plasma confinement and beam profile optimization. The program goals were to develop a plasma generator possessing the characteristics of high electrical efficiency (low eV/ion) and simplicity of operation while maintaining the reliability and durability of the conventional hollow cathode plasma sources. The RFI plasma generator has achieved minimum discharge losses of 120 eV/ion while the ECH generator has obtained 145 eV/ion, assuming a 90% ion optical transparency of the electrostatic acceleration system. Details of experimental tests with a variety of magnet configurations are presented.

Goede, H.↗
NASA NTRS1984

Effects of high energy radiation on the mechanical properties of epoxy-graphite fiber reinforced composites

The effects of high energy radiation on the mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites were assessed so that the durability of such composites in space applications could be predicted. Investigative techniques including ESR and infrared spectroscopy, ESCA, contact angle measurements, and dynamic and static mechanical testing (3-point bending and interlaminar shear) were employed. The results using these different techniques are individually described, and the implications of the data are discussed. The proposed plan of work for the next fiscal year is outlined.

Fornes, R. E.↗