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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 NTRS2009

Update on DOE Advanced IGCC/H2 Gas Turbine

Cooling Flow Reduction: a) Focus on improving turbine hot gas path part cooling efficiency. b) Applicable to current metallic turbine components and synergistic with advanced materials. c) Address challenges of IGCC/hydrogen fuel environment (for example, possible cooling hole plugging). Leakage Flow Reduction: a) Focus on decreasing turbine parasitic leakages, i.e. between static-to-static, static-to-rotating turbine parts. b) Develop improved seal designs in a variety of important areas. Purge Flow Reduction: a) Focus on decreasing required flows to keep rotor disk cavities within temperature limits. b) Develop improved sealing at the cavity rims and modified flow geometries to minimize hot gas ingestion and aerodynamic impact.

Chupp, Ray↗
NASA NTRS1993

Hot bubbles in a magnetic interstellar medium - Another look at the soft X-ray background

An attempt is made to understand the origin and properties of an isolated local bubble of hot gas using models of explosive events in a magnetic interstellar medium which mimic the local bubble in terms of the C band X-ray surface brightness and radius. The residual bubble of hot gas reaches a maximum size with an internal pressure below ambient, and then shrinks to smaller volume and a pressure nearly equal to ambient. The X-ray brightness reaches its minimum at the time of maximum radius and rises thereafter. It is found that the bubble growth must have been confined by a probably unacceptably large external pressure in order for the hot gas in the maximally extended cavity to radiate at a rate like that observed in the soft X-ray background.

Edgar, Richard J.↗
NASA NTRS1998

Hybrid IR-Gas Heater for Automated Tow Placement

A hybrid infrared-hot gas heat source has been developed and tested for the NASA Langley Tow Placement Facility. The IR heat source provides supplemental heat to the nip region. The additional heat is intended to reduce the need for conduction heating by the compaction roller, which causes (he roller to stick to the panel surface. Initial bench scale testing was performed to identify the most effective means of focusing IR energy into the nip region. A compact lamp and reflector that placed the lamp as close to the nip point as possible was found to deliver the highest heat flux in the nip region. A prototype heater was installed on the NASA Langley tow placement robot. Panels placed with a 400 C (sticking) compaction roller gave DCB initiation toughness numbers comparable to those reported for autoclave processed panels but were found to have unexpectedly high void contents. Placement with compaction roller temperatures that prevented roller sticking resulted in mode I fracture toughness approximately 70% that reported for autoclave processed panels. The variability in strength among specimens placed with reduced roller temperature was found to be greatly reduced, which implies that use of supplemental nip point heat may improve the robustness of the tow placement process. Use of the IR heat source permitted placement with a compaction roller temperature that would have resulted in negligible interfacial strength with the hot gas torch alone. The roller temperature reductions eliminated the need for the robot operator to attend placement operations.

Grenoble, Ray W.↗
NASA NTRS1990

Enhanced heat transfer rocket combustor technology component hot-fire test results

The evaluation of a method for enhancing combustor hot-gas wall heat extraction by using hot-fire tests of a rocket engine combustor calorimeter with hot-gas wall ribs is presented. The capability for enhanced heat extraction is required to increase available turbine drive energy for high chamber pressure operation, and therefore higher overall expander cycle engine performance. Determination of the rib effectiveness for incorporation into the design of a high-performance combustor for an advanced expander cycle combustor intended for use in an orbital transfer vehicle or advanced space engine, was the objective of these tests.

Brown, William S.↗
NASA NTRS2003

NGC7009: Testing the Wind-Wind Interaction Formation of Planetary Nebulae

We have successfully obtained the XMM-Newton observations of NGC 7009. X-ray emission is detected from the interior of NGC 7009, and it is definite resolved, indicating a plasma emission. We have carried out both a spatial analysis and a spectral analysis. The spatial analysis is limited by the angular resolution of the telescope. It is possible to confirm the existence of diffuse emission from hot gas, but the detailed distribution of the hot gas and the amount of stellar emission cannot be determined. The spectral analysis shows that the plasma temperature is only about 2 x 10(exp 6) K. This is the coolest PN interior ever detected. A mixing of shocked fast stellar wind and the cool nebular material is needed. The results of our analysis have been reported in a paper published in the Astronomy and Astrophysics Letters, as given below.

Chu, You-Hua↗
NASA NTRS1976

Rocket engine thrust chamber wall temperature distribution calculation and analysis

An analytical computational concept is presented which predicts the temperature profiles along a regeneratively cooled thrust chamber wall on the hot gas side and on the coolant side, and also the coolant bulk temperature profile. The computational model is based upon a coupling of the boundary layer heat transfer process with the heat transfer process through the chamber wall and the coolant flow heat absorption. The calculation is started with approximate temperature distributions for the hot gas side wall and the coolant flow. The iteration process of the computer program is terminated when the total heat transfer rates from the hot gas boundary layer to the wall and from the wall to the coolant are equal. The computer program for the integration of regenerative cooling process to a thrust chamber is kept general such that this program can be used with any boundary layer analysis computer program for temperature profile and heat transfer studies. A sample application of this concept is shown by using a boundary layer analysis program for the RL10 rocket engine thrust chamber.

Saha, H.↗
NASA NTRS1989

Superbubble blowout dynamics

Multiple supernovae and stellar winds from OB associations carve large holes filled with hot gas in the galactic disk. These superbubbles sweep up H I into cold, thin, dense shells and eventually grow large enough to blow completely out of the galactic H I disk. When superbubbles blow out of the disk, they vent hot gas and supernova energy into the galactic corona. In this paper ZEUS, a two-dimensional hydrodynamics code, is used to model the blowout of a superbubble from exponential and Gaussian models for the vertical density stratification. The results are compared to those from the Kompaneets (thin-shell) approximation. It is found that this approximation works very well, and that most of the mass of the shell remains in the plane, with 5 percent of it accelerating upward. The venting of the hot gas and the stability of the shell depends strongly on the model of the density distribution. It is suggested that the low galactic halo actually consists of a froth of merged superbubbles.

Mac Low, Mordecai-Mark↗
NASA NTRS2001

Understanding the Puzzling X-Ray Spectrum of the SO Galaxy NGC 4382; NGC 43819: Spectral Analysis of the Prototypical Early Merger and ASCA Observations of a Dynamically Young Elliptical: NGC 4125

We have analyzed the ASCA observations of NGC 4382, NGC 4038/9, NGC 4125 and produced papers for publication. NGC 4382 is one of the E and SO galaxies detected with the lowest X-ray to optical luminosity ratio. These galaxies have a peculiar X-ray (0.1-3 keV) spectrum, with a significant excess of counts in the lowest spectral channels (less than 1 keV) relative to the spectral count distributions of X-ray brihter E and SO galaxies. Analyzing the ROSAT PSPC observation of NGC 4382 it was unclear whether this soft excess was due to a real very soft component in a multi-component spectrum, or reflected an extremely low metal abundance in an isothermal hot gas. Our ASCA observations show that the low-abundance single-temperature model does not fit well to the X-ray spectrum, in agreement with our previous suggestions. A better explanation is a composite spectrum with a very soft component (0.3 keV) in addition to a harder (5 keV) component from X-ray binaries. In this model, the abundance cannot be constrained. More complex spectral models are also possible. The ASCA observations of The Antennae - (NGC4038/9) show that at least two spectral components are required to describe the emission-thermal emission from a plasma at 0.8 keV, and a component at higher energies. The hot gas contributes about half of the flux in the 0.5 to 6 keV band. If the column density to the higher energy component is greater than 2 x 10 (exp 21) per square centimeter, then the fitted abundance in the hot gas component is less than 0.2 solar. This low abundance is not expected for the hot interstellar medium in NGC4038/9 in which supernovae and star formation (expected to enrich and heat the gas) are ongoing. We do not detect any spatial variations in the spectrum. We relate these findings to data obtained by other satellites (Einstein, ROSAT) for this interacting galaxy pair. NGC4125's ASCA data was analyzed jointly with its Beppo-SAX observation. A hard component (kT /sim 4-10 keV) is observed together with a thermal component with line emission.

Fabbiano, Giuseppina↗
NASA NTRS2008

Investigation of Flow Instabilities in the Inlet Ducts of DP-1C VTOL Aircraft

An investigation of flow instabilities in the inlet ducts of a two-engine vertical takeoff and landing aircraft DP-1C is described in this report. Recent tests revealed that the engines stall during run ups while the aircraft is operating on the ground. These pop stalls occurred at relatively low power levels, sometimes as low as 60 percent of the engine full speed. Inability to run the engines up to the full speed level is attributed to in-ground effects associated with hot gas ingestion. Such pop stalls were never experienced when the aircraft was tested on a elevated grid platform, which ensured that the aircraft was operating in out-of-the-ground-effect conditions. Based on available information on problems experienced with other vertical takeoff and landing aircraft designs, it was assumed that the engine stalls were caused by partial ingestion of hot gases streaming forward from the main exit nozzle under the aircraft inlets, which are very close to the ground. It was also suggested that the nose wheel undercarriage, located between the inlets, may generate vortices or an unstable wake causing intense mixing of hot exit gases with incoming inlet flow, which would enhance the hot gas ingestion. After running a short three-day series of tests with fully instrumented engine inlets, it is now believed the most probable reason for engine pop stalls are random ingestions of a vortex generated between the two streams moving in opposite directions: outbound hot gas stream from the main nozzle close to the ground and inbound inlet flow above. Originally, the vortex is in a horizontal plane. However, at a certain velocity ratio of these two streams, the vortex attaches either to the ground or the aircraft surface at one end and the other end is swallowed by one of the aircraft inlets. Once the vortex enters the inlet duct, a puff of hot air can be sucked through the vortex core into the engine, which causes a serious inlet flow field distortion followed by an engine stall. Once the engine stalls, the outflow from the inlet pushes the vortex away and the engine resumes normal operation. This hypothesis needs to be verified experimentally; e.g., by extensive smoke flow visualization ahead of the aircraft inlets.

Lepicovsky, Jan↗
NASA NTRS2013

Modeling the Redshift Evolution of the Normal Galaxy X-Ray Luminosity Function

Emission from X-ray binaries (XRBs) is a major component of the total X-ray luminosity of normal galaxies, so X-ray studies of high-redshift galaxies allow us to probe the formation and evolution of XRBs on very long timescales (approximately 10 Gyr). In this paper, we present results from large-scale population synthesis models of binary populations in galaxies from z = 0 to approximately 20. We use as input into our modeling the Millennium II Cosmological Simulation and the updated semi-analytic galaxy catalog by Guo et al. to self-consistently account for the star formation history (SFH) and metallicity evolution of each galaxy. We run a grid of 192 models, varying all the parameters known from previous studies to affect the evolution of XRBs. We use our models and observationally derived prescriptions for hot gas emission to create theoretical galaxy X-ray luminosity functions (XLFs) for several redshift bins. Models with low common envelope efficiencies, a 50% twins mass ratio distribution, a steeper initial mass function exponent, and high stellar wind mass-loss rates best match observational results from Tzanavaris & Georgantopoulos, though they significantly underproduce bright early-type and very bright (L(sub x) greater than 10(exp 41)) late-type galaxies. These discrepancies are likely caused by uncertainties in hot gas emission and SFHs, active galactic nucleus contamination, and a lack of dynamically formed low-mass XRBs. In our highest likelihood models, we find that hot gas emission dominates the emission for most bright galaxies. We also find that the evolution of the normal galaxy X-ray luminosity density out to z = 4 is driven largely by XRBs in galaxies with X-ray luminosities between 10(exp 40) and 10(exp 41) erg s(exp −1).

Tremmel, M.↗
NASA NTRS2000

Shape Memory Alloy Actuator

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Robert J Baumbick↗
NASA NTRS2002

Shape Memory Alloy Actuator

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Robert J Baumbick↗
NASA NTRS1986

X-ray studies of galactic and intergalactic gas in the Pegasus I cluster

Einstein Observatory IPC observations of Pegasus I show hot gas in a low density intergalactic medium as well as in a galactic medium within each of the dominant elliptical galaxies, NGC 7619 and NGC 7626. The short central cooling times inferred, of 100 million years or less, suggest that the galaxies contain cooling flows of about 1 solar mass/yr. The intergalactic gas, which is about 5 times less dense than in the least dense of the known Abell clusters, is incapable of stripping the hot gas from the elliptical galaxies or the neutral gas from the spirals. The gas around NGC 7619 appears to be influencing one of the radio lobes of NGC 7626.

Canizares, C. R.↗
NASA NTRS1989

Steady state cooling flow models with gas loss for normal elliptical galaxies

A grid of cooling flow models for the hot gas in normal elliptical galaxies is calculated, including the loss of gas due to inhomogeneous cooling. The loss process is modeled as a distributed sink for the gas with the rate of loss being proportional to the local cooling rate. The cooling flow models with gas loss have smaller sonic radii, smaller inflow rates in their central regions, lower densities, and higher temperatures than homogeneous models. The reduction in the amount of hot gas flowing into the center of the models brings the models into much better agreement with the observed X-ray surface brightness profiles of elliptical galaxies. However, there is a large dispersion in the observed X-ray luminosities of ellipticals, and this cannot be explained by variations in the efficiency of gas loss. The gas-loss models have X-ray surface brightness profiles which are much less centrally peaked than the no-gas-loss models.

Sarazin, Craig L.↗
NASA NTRS1973

Earth storable bimodal engine, phase 1

An in-depth study of an Earth Storable Bimodal (ESB) Engine using earth storable propellants N2O/N2H4 and operating in either a monopropellant or bipropellant mode was conducted. Detailed studies were completed for both a hot-gas, regeneratively cooled thrust chamber and a ducted hot-gas, film cooled thrust chamber. Hydrazine decomposition products were used for cooling in either configuration. The various arrangements and configurations of hydrazine reactors, secondary injectors, chambers and gimbal methods were considered. The two basic materials selected for the major components were columbium alloys and L-605. The secondary injector types considered were previously demonstrated by JPL and consisted of a liquid-on-gas triplet, a liquid-on-gas doublet, and a liquid-on-gas coaxial injector. Various design tradeoffs were made with different reactor types located at: the secondary injector station, the thrust chamber throat, and the nozzle/extension interface. Associated thermal, structural, and mass analyses were completed.

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