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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Mixing and combustion of an underexpanded H2 jet in supersonic flow

Theoretical calculations are compared with experimental data in an investigation of the injection, mixing, and combustion of an underexpanded hydrogen jet in a supersonic test stream. The experimental tests in reacting and nonreacting flows were conducted by use of air and nitrogen as test media. Tests were conducted in a free jet and a ducted mode. Theoretical calculations were performed with a modified viscous characteristics analysis. The computer program employs finite rate chemistry and a turbulent viscosity model which varies radially and axially; it handles exit shock waves, expansion fans, and thermal compressions generated in the reacting flow fields. Comparison of the theory and experimental data indicates good agreement for the near flow field; this agreement is directly related to the explicit handling of the near-field shock and expansion waves. Less satisfactory agreement at downstream locations for both free jet and ducted flows is attributed to the lack of continued computation of the shocks and expansions in the far field.

Jenkins, R. V.↗
NASA NTRS1982

Symposium (International) on Combustion, 19th, Technion Israel Institute of Technology, Haifa, Israel, August 8-13, 1982, Proceedings

Topics discussed are related to elementary reactions, reaction mechanisms and modeling, laminar flames, flame chemistry, turbulent reacting shear flows, turbulent premixed flames, turbulent combustion measurements, continuous combustors, detonation, detonation and explosion, heterogeneous detonation, propellant combustion, fire-ignition and thermal degradation, fire-flame spread and burning, fire-modeling, spray combustion, and droplet combustion. Coal combustion kinetics and mechanisms are considered along with coal combustion mechanisms and pyrolysis, coal combustion techniques, NOx in coal combustion, gaseous pollutants, soot and PAH, soot and inorganic pollutants, I.C. engine combustion, and ignition and extinction. Attention is given to intricate paths and simple steps in chemical kinetics and combustion, the formation of polycyclic aromatic hydrocarbons by combustion, turbulent flame structure and speed in spark ignition engines, and unresolved problems in SOx, NOx, and soot control in combustion.

Source record↗
NASA NTRS1984

Cooling flows in clusters of galaxies

Cooling gas in the center of many clusters of galaxies is compressed and pushed inward by the thermal pressure of the hot, uncooled outer gas. Gravity acts as a focusing agent until the gas has cooled to galactic temperatures. The cooling process is thermally unstable, giving rise to optical filamentation. Once the gas cools below 10.000 K it presumably forms stars which add to the mass of a central galaxy. Accretion rates of up to 400 solar masses/yr are inferred from X-ray measurements so that the mass of such central galaxies may be due to cooling flows. Their optical and UV appearance emphasize that the gas predominantly turns into low-mass stars with an initial mass function unlike that of the solar neighborhood. Optical and X-ray observations of cooling flows can be used to investigate the continuing formation of the largest known galaxies.

Fabian, A. C.↗
NASA NTRS1985

Theoretical and experimental design studies for the Atmospheric General Circulation Experiment

The major criterion for the Atmospheric General Circulation Experiment (AGCE) design is that it be possible to realize strong baroclinic instability in the spherical configuration chosen. A configuration was selected in which a hemispherical shell of fluid is subjected to latitudinal temperature gradients on its spherical boundaries and the latitudinal boundaries are insulators. Work in the laboratory with a cylindrical version of this configuration revealed more instabilities than baroclinic instability. Since researchers fully expect these additional instabilities to appear in the spherical configuration also, they decided to continue the laboratory cylindrical annulus studies. Four flow regimes were identified: an axisymmetric Hadley circulation, boundary layer convection, baroclinic waves and deep thermal convection. Regime diagrams were prepared.

Fowlis, W. W.↗
NASA NTRS1987

Application of CFD codes to the design and development of propulsion systems

The internal flows of aerospace propulsion engines have certain common features that are amenable to analysis through Computational Fluid Dynamics (CFD) computer codes. Although the application of CFD to engineering problems in engines was delayed by the complexities associated with internal flows, many codes with different capabilities are now being used as routine design tools. This is illustrated by examples taken from the aircraft gas turbine engine of flows calculated with potential flow, Euler flow, parabolized Navier-Stokes, and Navier-Stokes codes. Likely future directions of CFD applied to engine flows are described, and current barriers to continued progress are highlighted. The potential importance of the Numerical Aerodynamic Simulator (NAS) to resolution of these difficulties is suggested.

Lord, W. K.↗
NASA NTRS1988

Quasi-Three-Dimensional Analysis Of Turbine Flow

Computer program reduces computer time and treats multiple elements. Improved design-analysis program for turbomachinery applied to multiple turbine elements simultaneously. Enables continuous and coherent analyses rather than previous piece-meal analyses of flow fields. Effects of upstream elements on downstream flow taken into account automatically.

Hsu, Wayne W.↗
NASA NTRS1987

The measurement of boundary layers on a compressor blade in cascade. I - A unique experimental facility

A unique cascade facility is described which makes it possible to use LDV for measuring blade boundary layer profiles. Because of the need for a laser access window, the facility cannot rely on continuous blade pack suction to achieve stable flow. Instead, a combination of tailboards and strong suction upstream of the blade pack is used to create a two-dimensional periodic flow field at a chord Reynolds number of 500,000. The distribution of the upstream suction is controlled through a complex baffling system. Details of the inlet and outlet flow are documented using five-hole pressure probes, blade static-pressure measurements, and sublimation flow visualization. Experimental data are presented on the flow field on the suction surface of the blade, the pressure surface, and near-wake flow fields.

Deutsch, Steven↗
NASA NTRS1988

Microgravity science at Langley Research Center

Although space research is still in an embryonic state, a combination of Earth based and space flight experiments are being coupled to yield a better understanding of the complex interaction of heat and fluid flow on the dynamics of crystal growth. Continued efforts on the ground as well as additional flight opportunities are needed to continue the drive to fully understand the advantages, both scientifically and economically, of microgravity crystal growth.

Fripp, Archibald L.↗
NASA NTRS1989

Initial supersonic combustion facility measurements

A combustion test tunnel designed for continuous operation to 2000 K was assembled. Flow quality of a Mach 2 nozzle for use with this tunnel was examined using an array of impact probes. The performance of gas shields used to protect optical windows was examined using both shadowgraphs and planar laser induced iodine fluorescence. High speed videography was used to aid in design of pressure relief panels related to hydrogen combustion testing safety.

Krauss, Roland H.↗
NASA NTRS1990

Use of satellite data and modeling to assess the influence of stratospheric processes on the troposphere

Current research focused on the examination of the effects of ozone heating and Newtonian cooling on the linear stability of transient planetary waves. A finite difference numerical model was developed in which the basic state wind, temperature, and ozone distributions were constructed using ground-based and satellite data. Preliminary results indicate that ozone dynamics interaction may play a more important role in the stability and maintenance of planetary waves than previously thought, particularly in summer when the mean solar zenith angle is smallest and thus ozone heating largest. Examination of the finite amplitude interactions among radiation, ozone, and dynamics was carried out. Self-consistent, coupled equations governing the weakly nonlinear interactions are currently being analyzed to provide a better understanding of wave-mean flow interactions and ozone transport in a continuously stratified model of the troposphere-stratosphere coupled system.

Nathan, Terrence↗
NASA NTRS1991

Particle flows to shape and voltage surface discontinuities in the electron sheath surrounding a high voltage solar array in LEO

This paper discusses the numerical modeling of electron flows from the sheath surrounding high positively biased objects in LEO (Low Earth Orbit) to regions of voltage or shape discontinuity on the biased surfaces. The sheath equations are derived from the Two-fluid, Warm Plasma Model. An equipotential corner and a plane containing strips of alternating voltage bias are treated in two dimensions. A self-consistent field solution of the sheath equations is outlined and is pursued through one cycle. The electron density field is determined by numerical solution of Poisson's equation for the electrostatic potential in the sheath using the NASCAP-LEO relation between electrostatic potential and charge density. Electron flows are calculated numerically from the electron continuity equation. Magnetic field effects are not treated.

Metz, Roger N.↗
NASA NTRS1991

Box schemes and their implementation on the iPSC/860

Research on algoriths for efficiently solving fluid flow problems on massively parallel computers is continued in the present paper. Attention is given to the implementation of a box scheme on the iPSC/860, a massively parallel computer with a peak speed of 10 Gflops and a memory of 128 Mwords. A domain decomposition approach to parallelism is used.

Chattot, J. J.↗
NASA NTRS1990

Observations of filamentary field-aligned current coupling between the magnetospheric boundary layer and the ionosphere

A distinct class of dayside high-latitude magnetic pulsations can be identified from the spatial characteristics of the disturbance field. These pulsations exhibit traveling radial patterns such as would result from moving filaments of field-aligned current interacting with the ionosphere to produce cells of Hall current and vortexlike plasma flow. Time intervals containing a series of continuous multiple vortices are investigated here. The vortices occur on the boundary between sunward and antisunward ionospheric plasma convection. Low altitude DMSP satellite particle measurements indicate that the vortices are on magnetic field lines which map to the inner edge of the magnetospheric low latitude boundary layer. No repetitive solar wind disturbance (e.g., pressure variations) appears to be associated with the events, suggesting that the vortices are related to a local magnetospheric instability. No strong correlation between interplanetary field conditions and the detection of vortices is found.

Clauer, C. R.↗
NASA NTRS1992

Calorimetric determination of the thermoneutral potential of Li/BCX and Li/SOCl2 cells

Results are presented of the calorimetric determination of the effective thermoneutral potential, Eetp, of Li/BCS and Li/SOCl2 cells in the temperature range 0-60 C through a continuous recording of the cell voltage, heat flow, and current. The average effective thermoneutral potential at 25 C was 4.0 and 3.84 V for BCX and Li/SOCl2 cells, respectively. Based on the classical approach, the reversible cell potential, Er, and temperature dependence of reversible cell potential, dEr/dT, for BCX cell were 3.74 V and -0.952 mV/K, respectively, and for Li/SOCl2, Er = 3.67 V and dEr/dT = 0.567 mV/K. The thermal polarization (Eetp-E1), where E1 is the load voltage, for both cells, showed that they are the most thermally efficient near 40 C. An overall reaction proposed for the BCX chemistry is supported by the calculated thermodynamic parameters.

Kalu, E. E.↗
NASA NTRS1993

Variable Refractive Index Effects on Radiation in Semitransparent Scattering Multilayered Regions

A simple set of equations is derived for predicting the temperature distribution and radiative energy flow in a semitransparent layer consisting of an arbitrary number of laminated sublayers that absorb, emit, and scatter radiation. Each sublayer can have a different refractive index and optical thickness. The plane composite region is heated on each exterior side by a different amount of incident radiation. The results are for the limiting case where heat conduction within the layers is very small relative to radiative transfer, and is neglected. The interfaces are assumed diffuse, and all interface reflections are included in the analysis. The thermal behavior is readily calculated from the analytical expressions that are obtained. By using many sublayers, expressions provide the temperature distribution and heat flow for a diffusing medium with a continually varying refractive index, including internal reflection effects caused by refractive index gradients. Temperature and heat flux results are given to show the effect of variations in refractive index and optical thickness through the multilayer laminate.

Siegel, R.↗
NASA NTRS1994

Air Force seal activities

Seal technology development is an important part of the Air Force's participation in the Integrated High Performance Turbine Engine Technology (IHPTET) initiative, the joint DOD, NASA, ARPA, and industry endeavor to double turbine engine capabilities by the turn of the century. Significant performance and efficiency improvements can be obtained through reducing internal flow system leakage, but seal environment requirements continue to become more extreme as the engine thermodynamic cycles advance towards these IHPTET goals. Brush seal technology continues to be pursued by the Air Force to reduce leakage at the required conditions. Likewise, challenges in engine mainshaft air/oil seals are also being addressed. Counter-rotating intershaft applications within the IHPTET initiative involve very high rubbing velocities. This viewgraph presentation briefly describes past and current seal research and development programs and gives a summary of seal applications in demonstrator and developmental engine testing.

Mayhew, Ellen R.↗
NASA NTRS1996

Air Force Seal Programs

Seal technology development is an important part of the Air Force's participation in the Integrated High Performance Turbine Engine Technology (IHPTET) initiative, the joint DOD, NASA, ARPA, and industry endeavor to double turbine engine capabilities by the turn of the century. Significant performance and efficiency improvements can be obtained through reducing internal flow system leakage, but seal environment requirements continue to become more extreme as the engine thermodynamic cycles advance towards these IHPTET goals. Seal technology continues to be pursued by the Air Force to control leakage at the required conditions. This presentation briefly describes current seal research and development programs and gives a summary of seal applications in demonstrator and developmental engines.

Mayhew, Ellen R.↗
NASA NTRS2000

The Solar Convection Spectrum

I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

Bachmann, Kurt T.↗