Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “grade”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

An Experimental Evaluation of Oil Pumping Rings

The design and construction of a reciprocating test vehicle to be used in evaluating hydrodynamic oil pumping rings are discussed. In addition, experimental test data are presented for three pumping ring designs that were constructed from Tin-Based Babbitt (SAE 11), Bearing Bronze (SAE 660), and Mechanical Carbon Graphite (Union Carbide Grade CNF-J). Data of pumped flow rate versus delivered pressure, as well as friction loss, are reported for the following conditions: frequencies of 10, 35 and 45 Hz; strokes of 25.4 mm (1.00 in.), 38.1 mm (1.50 in.) and 50.8 mm (2.00 in.) oil inlet temperature of 49 degrees (120 degrees); and pumping ring close-in pressures of 10.3 MPa (1500 lb/square inch. A 20W40 automotive oil was used for all tests. The maximum delivered pressure was 11 MPa (1600 lb/square inch. An analysis of hydrodynamic oil pumping rings was performed and the results of the analysis were compared to measured test data.

Eusepi, M. W.↗
NASA NTRS1981

Silicon materials task of the low-cost solar array project. Phase 4: Effects of impurities and processing on silicon solar cells

The results of the study form a basis for silicon producers, wafer manufacturers, and cell fabricators to develop appropriate cost-benefit relationships for the use of less pure, less costly solar grade silicon. Cr is highly mobile in silicon even at temperatures as low as 600 C. Contrasting with earlier data for Mo, Ti, and V, Cr concentrations vary from place to place in polycrystalline silicon wafers and the electrically-active Cr concentration in the polysilicon is more than an order of magnitude smaller than would be projected from single crystal impurity data. We hypothesize that Cr diffuses during ingot cooldown after growth, preferentially segregates to grain and becomes electrically deactivated. Accelerated aging data from Ni-contaminated silicon imply that no significant impurity-induced cell performance reduction should be expected over a twenty year device lifetime.

Hopkins, R. H.↗
NASA NTRS1981

Evaluation and verification of epitaxial process sequence for silicon solar-cell production

Several process sequences are shown to be of potentially low cost and to perform effectively when applied to the high quality silicon crystals for which they were developed. The extent to which such process sequences can also perform effectively when applied to lower cost thin film solar cells formed by epitaxial deposition of Si on potentially inexpensive substrates of upgraded metallurgical grade Si was investigated.

Redfield, D.↗
NASA NTRS1981

Silicon materials task of the low-cost solar array project. Phase 4: Effects of impurities and processing on silicon solar cells

The effects of impurities, various thermochemical processes, and any impurity-process interactions upon the performance of terrestrial solar cells are defined. The results form a basis for silicon producers, wafer manufacturers, and cell fabricators to develop appropriate cost benefit relationships for the use of less pure, less costly solar grade silicon.

Hopkins, R. H.↗
NASA NTRS1981

Cataract production in mice by heavy charged particles

The cataractogenic effects of heavy charged particles are evaluated in mice in relation to dose and ionization density. The relative biological effectiveness in relation to linear energy transfer for various particles is considered. Results indicated that low single doses (5 to 20 rad) of Fe 56 or Ar 40 particles are cataractogenic at 11 to 18 months after irradiation; onset and density of the opacification are dose related and cataract density (grade) at 9, 11, 13, and 16 months after irradiation shows partial linear energy transfer dependence. The severity of cataracts is reduced significantly when 417 rad of Co 60 gamma radiation is given in 24 weekly 17 rad fractions compared to giving this radiation as a single dose, but cataract severity is not reduced by fractionation of C12 doses over 24 weeks.

Ainsworth, E. J.↗
NASA NTRS1981

Silicon production process evaluations

The chemical engineering analysis of the preliminary process design of a process for producing solar cell grade silicon from dichlorosilane is presented. A plant to produce 1,000 MT/yr of silicon is analyzed. Progress and status for the plant design are reported for the primary activities of base case conditions (60 percent), reaction chemistry (50 percent), process flow diagram (35 percent), energy balance (10 percent), property data (10 percent) and equipment design (5 percent).

Source record↗
NASA NTRS1981

Steam engine research for solar parabolic dish

The parabolic dish solar concentrator provides an opportunity to generate high grade energy in a modular system. Most of the capital is projected to be in the dish and its installation. Assurance of a high production demand of a standard dish could lead to dramatic cost reductions. High production volume in turn depends upon maximum application flexibility by providing energy output options, e.g., heat, electricity, chemicals and combinations thereof. Subsets of these options include energy storage and combustion assist. A steam engine design and experimental program is described which investigate the efficiency potential of a small 25 kW compound reheat cycle piston engine. An engine efficiency of 35 percent is estimated for a 700 C steam temperature from the solar receiver.

Demler, R. L.↗
NASA NTRS1981

Catalytic combustion with incompletely vaporized residual fuel

Catalytic combustion of fuel lean mixtures of incompletely vaporized residual fuel and air was investigated. The 7.6 cm diameter, graded cell reactor was constructed from zirconia spinel substrate and catalyzed with a noble metal catalyst. Streams of luminous particles exited the rector as a result of fuel deposition and carbonization on the substrate. Similar results were obtained with blends of No. 6 and No. 2 oil. Blends of shale residual oil and No. 2 oil resulted in stable operation. In shale oil blends the combustor performance degraded with a reduced degree of fuel vaporization. In tests performed with No. 2 oil a similar effect was observed.

Rosfjord, T. J.↗
NASA NTRS1981

Evaluation and verification of epitaxial process sequence for silicon solar cell production

The applicability of solar cell and module processing sequences, to be used on lower cost epitaxial silicon wafers was evaluated. The extent to which the process sequences perform effectively when applied to film solar cells formed by epitaxial deposition of Si on potentially inexpensive substrates of upgraded metallurgical grade Si is examined. It is concluded that these substrates are satisfactory in their cell performance.

Redfield, D.↗
NASA NTRS1980

Control of volume resistivity in inorganic-organic separators

Control of resistivity in NASA inorganic-organic separators is achieved by incorporating small percentages of high surface area, fine-particle silica with other ingredients in the separator coating. The volume resistivity appears to be predictable from coating composition, that is, from the surface area of filler particles in the coating. The approach has been applied to two polymer-'plasticizer'-filler coating systems, where the filler content of each is below the generally acknowledged critical pigment volume concentration of the coating. Application of these coating systems to 0.0254 cm thick (10 mil) fuel-cell grade asbestos sheet produces inexpensive, flexible, microporous separators that perform at least as well as the original inorganic-organic concept, the Astropower separator.

Sheibley, D. W.↗
NASA NTRS1980

Carbonic metamorphism, granulites and crustal growth

Stabilization of early crust against melting by high radioactivity and against resorption into the mantle by fast convective overturn requires that water and heat producers were flushed upwards within 50 Myr of accretion. Creation of a refractory base of granulite by metamorphism associated with CO2 vapour explains CO2-rich fluid inclusions in ancient high-grade rocks, minor-element depletions and local phenomena of arrested development of charnockite in Precambrian terrains. The hot-spot and plate-tectonic models of Precambrian crustal evolution lead to different schemes for CO2 delivery to continental roots. New tectonic concepts may be needed to explain carbonic metamorphism and other features of early crustal evolution.

Newton, R. C.↗
NASA NTRS1980

Thermal barrier coatings for heat engine components

A comprehensive NASA-Lewis program of coating development for aircraft gas turbine blades and vanes is presented. Improved ceramic layer compositions are investigated, along the MCrAlY bond films and the methods of uniform deposition of the coatings; the thermomechanical and fuel impurity tolerance limits of the coatings are being studied. Materials include the ZrO2-Y2O3/NiCrAlY system; the effects of the bond coat and zirconia composition on coating life and Mach 1 burner rig test results are discussed. It is concluded that Diesel engines can also utilize thermal barrier coatings; they have been used successfully on piston crowns and exhaust valves of shipboard engines to combat lower grade fuel combustion corrosion.

Levine, S. R.↗
NASA NTRS1980

Shear heating and the state of stress on faults

Evidence for shear heating associated with crustal faulting is described for a number of fault zones in a wide variety of tectonic environments. It is shown that a thermal anomaly associated with the fault has resulted in the metamorphism of adjacent rocks to higher grades than can be accounted for by considering other heat sources. If relative displacements across these faults occurred at plate tectonic rates or slower, then shear stresses of a kilobar or so must have existed on the faults in order to produce the observed shear heating.

Scholz, C. H.↗
NASA NTRS1981

Effect of zinc impurity on silicon solar-cell efficiency

Zinc is a major residue impurity in the preparation of solar-grade silicon material by the zinc vapor reduction of silicon tetrachloride. This paper projects that in order to get a 17-percent AM1 cell efficiency for the Block IV module of the Low-Cost Solar Array Project, the concentration of the zinc recombination centers in the base region of silicon solar cells must be less than 4 x 10 to the 11th Zn/cu cm in the p-base n+/p/p+ cell and 7 x 10 to the 11th Zn/cu cm in the n-base p+/n/n+ cell for a base dopant impurity concentration of 5 x 10 to the 14 atoms/cu cm. If the base dopant impurity concentration is increased by a factor of 10 to 5 x 10 to the 15th atoms/cu cm, then the maximum allowable zinc concentration is increased by a factor of about two for a 17-percent AM1 efficiency. The thermal equilibrium electron and hole recombination and generation rates at the double-acceptor zinc centers are obtained from previous high-field measurements as well as new measurements at zero field described in this paper. These rates are used in the exact dc-circuit model to compute the projections.

Sah, C.-T.↗
NASA NTRS1981

Recrystallization of polycrystalline silicon

Optical metallography is used to investigate the recrystallization properties of polycrystalline semiconductor-grade silicon. It is found that polycrystalline silicon recrystallizes at 1380 C in relatively short times, provided that the prior deformation is greater than 30%. For a prior deformation of about 40%, the recrystallization process is essentially complete in about 30 minutes. Silicon recrystallizes at a substantially slower rate than metals at equivalent homologous temperatures. The recrystallized grain size is insensitive to the amount of prestrain for strains in the range of 10-50%.

Lall, C.↗
NASA NTRS1981

Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems

This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.

Ramakumar, R.↗
NASA NTRS1981

Shuttle Student Involvement Project for Secondary Schools

The National Aeronautics and Space Administration (NASA) has initiated the Shuttle Student Involvement Project for Secondary Schools (SSIP-S), an annual nationwide competition to select student proposals for experiments suitable for flight aboard the Space Shuttle. The objective of the project is to stimulate the study of science and technology in grades 9 through 12 by directly relating students to a space research program. This paper will analyze the first year of the project from a standpoint of how the competition was administered; the number and types of proposals that were submitted; and will discuss the process involved in preparing the winning experiments for eventual flight.

Wilson, G. P.↗
NASA NTRS1981

Solar flare irradiation records in Antarctic meteorites

The observation of tracks from solar flare heavy nuclei in Antarctic meteorite samples is reported. In an analysis of nuclear track densities in eight L and H chondrites of low metamorphic grade, it was found that two interior specimens of sample 77216, an L-3 chondrite, contain olivine grains with track densities much higher than the average track densities, indicating precompaction irradiation by solar flares in different shielding conditions. Preliminary data from mass spectroscopic analyses show a large excess of noble gases, with a Ne-20/Ne-22 ratio of greater than or equal to 10, indicating the presence of solar-type noble gas. Results of track density measurements in the other Antarctic meteorites range from 10,000 to 4,000,000/sq cm, which is within the range observed in non-Antarctic L-group meteorites

Goswami, J. N.↗