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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Dielectronic recombination rates, ionization equilibrium, and radiative energy-loss rates for neon, magnesium, and sulfur ions in low-density plasmas

Results of detailed and systematic calculations are presented for the total dielectronic recombination rate coefficients for the ions of Ne, Mg, and S in a low-density predominantly hydrogen plasma. The new recombination rates are used to calculate solar corona ionization-equilibrium distributions of the ions. The most important effect of dielectronic recombination for ions in corona equilibrium is found to be a shift in the maximum-abundance temperatures toward higher temperatures, which are in some cases reduced from those predicted on the basis of the simple Burgess formula.

Jacobs, V. L.↗
NASA NTRS1980

A probabilistic approach to radiative energy loss calculations for optically thick atmospheres - Hydrogen lines and continua

An approximate probabilistic radiative transfer equation and the statistical equilibrium equations are simultaneously solved for a model hydrogen atom consisting of three bound levels and ionization continuum. The transfer equation for L-alpha, L-beta, H-alpha, and the Lyman continuum is explicitly solved assuming complete redistribution. The accuracy of this approach is tested by comparing source functions and radiative loss rates to values obtained with a method that solves the exact transfer equation. Two recent model solar-flare chromospheres are used for this test. It is shown that for the test atmospheres the probabilistic method gives values of the radiative loss rate that are characteristically good to a factor of 2. The advantage of this probabilistic approach is that it retains a description of the dominant physical processes of radiative transfer in the complete redistribution case, yet it achieves a major reduction in computational requirements.

Canfield, R. C.↗
NASA NTRS1986

A study of the stochastic energization of charged particles with and without synchrotron energy loss

A momentum-diffusion formulation that takes the initial values of the particle distribution functions and momentum-space boundary conditions is presently employed for the computational and analytical study of the stochastic energization of charged particles by plasma waves. The nature of the particle distribution functions resulting from stochastic energization and the validity of the momentum-diffusion formulation for the energization are determined. The validity of the momentum-diffusion formulation with power law diffusion coefficients is assessed.

Borovsky, J. E.↗
NASA NTRS1937

Energy Loss, Velocity Distribution, and Temperature Distribution for a Baffled Cylinder Model

A study has been made of the important principles involved in the operation of a baffle for an engine cylinder and shows that cooling can be improved by 20 percent by using a correctly designed baffle. Such a gain is as effective as a 65 percent increase in pressure drop across the standard baffle, which had a 1/4 inch clearance between baffle and fin tips.

Brevoort, Maurice J↗
NASA NTRS1994

An analysis code for the Rapid Engineering Estimation of Momentum and Energy Losses (REMEL)

Nonideal behavior has traditionally been modeled by defining efficiency (a comparison between actual and isentropic processes), and subsequent specification by empirical or heuristic methods. With the increasing complexity of aeropropulsion system designs, the reliability of these more traditional methods is uncertain. Computational fluid dynamics (CFD) and experimental methods can provide this information but are expensive in terms of human resources, cost, and time. This report discusses an alternative to empirical and CFD methods by applying classical analytical techniques and a simplified flow model to provide rapid engineering estimates of these losses based on steady, quasi-one-dimensional governing equations including viscous and heat transfer terms (estimated by Reynold's analogy). A preliminary verification of REMEL has been compared with full Navier-Stokes (FNS) and CFD boundary layer computations for several high-speed inlet and forebody designs. Current methods compare quite well with more complex method results and solutions compare very well with simple degenerate and asymptotic results such as Fanno flow, isentropic variable area flow, and a newly developed, combined variable area duct with friction flow solution. These solution comparisons may offer an alternative to transitional and CFD-intense methods for the rapid estimation of viscous and heat transfer losses in aeropropulsion systems.

Dechant, Lawrence J.↗
NASA NTRS2003

Electron Energy-Loss Spectroscopy (EELS) of Fe-bearing Sheet Silicates in CM Chondrites

The primitive character and hydrated mineralogy of the CM chondrites offers insight into some of the earliest reactions between solids and water. Such reactions profoundly affected the matrices and fine-grained rims (FGRs) [1-4], two of the most significant components of these meteorites [5]. We are using EELS combined with a transmission electron microscope (TEM) to investigate the compositions of Fe-bearing minerals, with emphasis on determining oxidation states and quantification of oxidation-state ratios. Iron is among the most abundant elements in the solar system and it can occur naturally in three oxidation states: Fe0, Fe2+, and Fe3+. Determination of oxidation- state ratios is useful because they can be used to infer the redox conditions under which the minerals formed or were last equilibrated [6, 7]. We are particularly interested in understanding how the oxidation state of Fe was affected by the aqueous reactions of the CM chondrites.

Zega, Thomas J.↗
NASA NTRS1945

The Minimum Energy Loss Propeller

Various cases are presented of the solution of the problem ot the most efficient propeller, more general cases being considered than the one by Betz in 1919: namely, that of a propeller under a limiting light load, The problem is solved directly and also with the aid of the Ritz method which became readily applicable after the author proposed a method for the solution of the propeller problem, in general, with the aid of trigonometric series. The design of a propeller with the aid of this method is given and an analysis is made of the effect of the fuselage and of the viscosity coefficient mu on the character of the solution of the variational problem.

Poliakhov, N.↗
NASA NTRS1937

Energy Loss, Velocity Distribution, and Temperature Distribution for a Baffled Cylinder Model, Special Report

In the design of a cowling a certain pressure drop across the cylinders of a radial air-cooled engine is made available. Baffles are designed to make use of this available pressure drop for cooling. The problem of cooling an air-cooled engine cylinder has been treated, for the most part, from considerations of a large heat-transfer coefficient. The knowledge of the precise cylinder characteristics that give a maximum heat-transfer coefficient should be the first consideration. The next problem is to distribute this ability to cool so that the cylinder cools uniformly. This report takes up the problem of the design of a baffle for a model cylinder. A study has been made of the important principles involved in the operation of a baffle for an engine cylinder and shows that the cooling can be improved 20% by using a correctly designed baffle. Such a gain is as effective in cooling the cylinder with the improved baffle as a 65% increase in pressure drop across the standard baffle and fin tips.

Brevoort, Maurice J.↗
DOE OSTI2020

Algae cultivation systems and methods with reduced energy loss

An open raceway algae cultivation system includes a channel configured to contain an algae cultivation fluid. The channel includes a contraction zone having a width and a depth. A pump is configured to circulate the algae cultivation fluid in the channel. A width of the contraction zone decreases leading into the entrance of the pump and a depth of the contraction zone is greater than a depth of at least a portion of the channel located outside of the contraction zone.

42 ENGINEERING↗
NASA NTRS1990

Characterization of hydrogen interactions with the surface of alpha-2 titanium aluminide alloys

The interaction of hydrogen at the surface of alpha-2 titanium aluminide alloys with Nb additions has been investigated with Auger electron spectroscopy (AES) and reflected electron energy loss (REELS) spectroscopy. The hydrogen was either adsorbed onto the alloy surface from the gas phase or it was pre-charged into the alloy forming an alpha-2 hydride. No effect of either adsorbed or absorbed hydrogen was observed in the Auger spectra. A shift in the bulk plasmon loss energy (observed with REELS) was measured for both conditions. The potential significance of these results in relation to hydrogen interactions in this alloy is discussed.

Shanabarger, Mickey R.↗
NASA NTRS1980

Generalized shading analysis for paraboloidal collector fields

This paper presents the development and results of a generalized shading analysis for a field of point-focus parabolic dish concentrators. Shading of one concentrator by another with attendant loss of energy is a function of the position of the sun and the relative locations of the concentrators within the field. A method is presented for determining the annualized energy loss which includes a trade-off of system life-cycle energy as a function of concentrator spacing and field geometric layout. System energy output is computed on an annualized basis, employing 15 minute-increment environmental data tapes for the year 1976 at Barstow, California. For a land cost of $5000 per acre, lowest system energy cost occurs at about a 25 percent packing fraction (concentrator area/land area) for a typical 1-MWe dish-Stirling solar thermal power plant. Basic equations are given for computing the shading and concomitant energy loss as a function of concentrator center-to-center spacing, field layout site location.

Osborn, D. B.↗