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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Effect of a semi-annular thermal acoustic shield on jet exhaust noise

The effect of a semi-annular acoustic shield on jet exhaust noise is investigated with the rationale that such a configuration would reduce or eliminate the multiple reflection mechanism. A limited range of flow conditions for one nozzle/shield configuration were studied at model scale. Noise measurements for a 10 cm conical nozzle with a semi-annular acoustical shield are presented in terms of lossless free field data at various angular locations with respect to the nozzle. Measurements were made on both the shielded and unshielded sides of the nozzle. Model scale overall sound pressure level directivity patterns and comparisons of model scale spectral data are provided. The results show that a semi-annular thermal acoustic shield consisting of a low velocity, high temperature gas stream partially surrounding a central jet exhibits lower noise levels than when the central jet is operated alone. The results are presented parametrically, showing the effects of various shield and central system velocities and temperatures.

Goodykoontz, J.↗
NASA NTRS1982

Method of protecting a surface with a silicon-slurry/aluminide coating

A low cost coating for protecting metallic base system substrates from high temperatures, high gas velocity oxidation, thermal fatigue and hot corrosion is described. The coating is particularly useful for protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrate from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue. Also, the Si-Al coating increased the resistance of certain superalloys to hot corrosion.

Deadmore, D. L.↗
NASA NTRS1982

Ultraviolet observations of stellar chromospheric activity

A survey is presented of chromospheric and transition region (TR) line emission in late-type stars obtained with the IUE satellite. A wide variation in TR emission (ions formed near T = 100,000 K) at a given position in the H-R diagram is found, contradicting theories that incorporate only acoustic energy generation and deposition. The behavior of the Hyades giants is thought to suggest that age does not uniquely determine emission levels. The data are consistent with the picture advanced by many others that rapid rotation appears to result in enhanced fluxes. Emission in TR lines is correlated with chromospheric emission; the range in observed surface fluxes from different stars increases with the temperature of line formation. It is noted that although emission measures of high temperature gas generally decline with decreasing stellar gravity, it is not possible to define a sharp division in the H-R diagram between stars with TR emitting regions and those without.

Hartmann, L.↗
NASA NTRS1982

Detection of interstellar NH sub 3 in the far-warm and dense gas in Orion-KL

The detection of the (J,K) = a(4,3) yields s(3,3) rotation inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region is reported. The line is in emission and has a FWHM or = to 30 km s 0.15. The far IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3) yields s(3,3) line is very optically thick, and since it is seen in emission, radiative excitation of the (4,3) NH3 level by far IR emission from dust within the source can be ruled out. Radiative excitation via the 10 microns of vibrational transitions of NH3 also seems unlikely. Hence, the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Since the far IR line emission is highly trapped, densities of approximately 10 to the 7th power cu cm are high enough to explain the observations. Shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.↗
NASA NTRS1983

Silicon-slurry/aluminide coating

A low cost coating protects metallic base system substrates from high temperatures, high gas velocity ovidation, thermal fatigue and hot corrosion and is particularly useful fo protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrates from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue and increased the resistance of certain superalloys to hot corrosion.

Deadmore, D. L.↗
NASA NTRS1983

Detection of interstellar NH3 in the far-infrared - Warm and dense gas in Orion-KL

Results of an investigation are presented which show the detection of the (J,K) = a(4,3)-s(3,3) rotation-inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region. The line is found to be in emission and has a FWHM greater than or equal to 30 km/s, while the far-IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3)-s(3,3) line is very optically thick and it is determined that radiative excitation of the (4,3) NH3 level by far-IR emission from dust within the source can be ruled out. It is concluded that the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Densities of approximately 10 to the 7th/cu cm are high enough to explain the observations, while shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.↗
NASA NTRS1986

Research instrumentation for hot section components of turbine engines

Programs to develop research instrumentation for use on hot section components of turbine engines are discussed. These programs can be separated into two categories: one category includes instruments which can measure the environment within the combustor and turbine components, the other includes instruments which measure the response of engine components to the imposed environment. Included in the first category are instruments to measure total heat flux and fluctuating gas temperature. High temperature strain measuring systems, thin film sensors (e.g., turbine blade thermocouples) and a system to view the interior of a combustor during engine operation are programs which comprise the second category. The paper will describe the state of development of these sensors and measuring systems and, in some cases, show examples of measurements made with this instrumentation. The discussion will cover work done at NASA Lewis and at various contractor facilities.

Englund, D. R.↗
NASA NTRS1986

Spectroscopy of the extreme ultraviolet background radiation

Observations in the FUV and soft X-ray bands suggest that the interstellar medium contains several components of high-temperature gas and should be emitting in the EUV. Indeed, diffuse radiation has been detected in the EUV with photometric instruments, but no special measurements exist below 520 A. A unique grazing-incidence spectrometer has been designed to study the diffuse emission between 80 and 650 A with 10 to 20-A resolution. The instrument was launched on a Black Brant sounding rocket from White Sands Missile Range on April 22, 1986. Preliminary analysis shows the expected geocoronal and interplanetary He I 584-A emission, and possibly other features which may originate in the hot ionized interstellar gas. Flux limits to these possible emission lines are compatible with previous broadband measurements.

Labov, Simon↗
NASA NTRS1987

Forbidden coronal iron line images of Puppis A - Cloud evaporation or shocked cloud?

Calibrated CCD images of the eastern X-ray knot in Puppis A, made in the forbidden red and green coronal Fe lines, are discussed. They show the high-temperature gas to have a rich morphology, with the scale of some features approaching the 2.6 arcsec resolution of the data. The pictures have been compared with an Einstein HRI soft X-ray image; there is close correspondence in the position and size of structures seen in the optical forbidden lines and in the X-rays. Located near the shock front a cloud of about 0.4 pc x 0.9 pc dimension shines brilliantly in the 5303 A line. To test the hypothesis that the cloud might be evaporating into the remnant interior, the 5303 A and 6374 A intensity distributions expected for a steady state, one-fluid evaporatig model have been computed.

Teske, Richard G.↗
NASA NTRS1988

HOST turbine heat transfer program summary

The objectives of the HOST Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding with the remainder going to analytical efforts. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base.

Heat transfer↗
NASA NTRS1988

Numerical simulation of hypersonic inlet flows with equilibrium or finite rate chemistry

An efficient numerical program incorporated with comprehensive high temperature gas property models has been developed to simulate hypersonic inlet flows. The computer program employs an implicit lower-upper time marching scheme to solve the two-dimensional Navier-Stokes equations with variable thermodynamic and transport properties. Both finite-rate and local-equilibrium approaches are adopted in the chemical reaction model for dissociation and ionization of the inlet air. In the finite rate approach, eleven species equations coupled with fluid dynamic equations are solved simultaneously. In the local-equilibrium approach, instead of solving species equations, an efficient chemical equilibrium package has been developed and incorporated into the flow code to obtain chemical compositions directly. Gas properties for the reaction products species are calculated by methods of statistical mechanics and fit to a polynomial form for C(p). In the present study, since the chemical reaction time is comparable to the flow residence time, the local-equilibrium model underpredicts the temperature in the shock layer. Significant differences of predicted chemical compositions in shock layer between finite rate and local-equilibrium approaches have been observed.

Yu, Sheng-Tao↗
NASA NTRS1988

Review and assessment of the database and numerical modeling for turbine heat transfer

The objectives of the HOST Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high-temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding while the analytical efforts were approximately 25 percent. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base.

Gladden, H. J.↗
NASA NTRS1989

Review and assessment of the database and numerical modeling for turbine heat transfer

The objectives of the NASA Hot Section Technology (HOST) Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high-temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding while the analytical efforts were approximately 25 percent. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base.

H J Gladden↗
NASA NTRS1988

Spectral observations of the extreme ultraviolet astronomical background radiation

Observations in the FUV and soft X-ray bands suggest that the ISM contains several components of high-temperature gas (100,000-1 million K). If large volumes of local interstellar space are filled with this hot plasma, emission lines will be produced in the EUV. Diffuse EUV radiation, however, has only been detected with photometric instruments; no spectral measurements exist below 520 A. A unique grazing-incidence spectrometer to study the diffuse emission between 80 and 650 A with resolution 10-30 A was successfully flown on a sounding rocket in April 1986, and a preliminary analysis reveals several features. In addition to the expected interplanetary He I 584 A emission and the geocoronal He II 304 A emission, other features appear which may orginate in the hot ionized interstellar gas.

Labov, S.↗
NASA NTRS1985

Ceramic composition

Novel transformation toughened ceramic compositions comprising finely divided Zr0 2 -Hf0 2 solid solution particles dispersed in a Al 2 0 3 -Cr 2 0 3 (alumina) or 3Al 2 0 3 .2Si0 2 -3Cr 2 0 3 .2Si0 2 (mullite) solid solution matrix phase. It is found that increased hardness and modulus associated with higher relative Cr 2 0 3 content (e.g. 20 mole % ) in the matrix phase and increased fracture toughness associated with higher relative Hf0 2 content ( e.g. 10 to 20 mole % ) in the disperse phase represent viable and improved ceramic compositions. Such transformation toughened ceramic compositions are considered useful in superhot light diesel engine applications, high temperature gas turbines and ultrahigh temperature ceramic heat exchangers.

Tseng-Ying Tien↗
NASA NTRS1991

Nuclear fuels status

A discussion on coated particle fuel performance from a modular High Temperature Gas Reactor (HTGR) is presented along with experimental results. The following topics are covered: (1) the coated particle fuel concept; (2) the functional requirements; (3) performance limiting mechanisms; (4) fuel performance; and (5) methods/techniques for characterizing performance.

Kania, Michael↗
NASA NTRS1992

Closed Brayton Cycle power system with a high temperature pellet bed reactor heat source for NEP applications

Capitalizing on past and future development of high temperature gas reactor (HTGR) technology, a low mass 15 MWe closed gas turbine cycle power system using a pellet bed reactor heating helium working fluid is proposed for Nuclear Electric Propulsion (NEP) applications. Although the design of this directly coupled system architecture, comprising the reactor/power system/space radiator subsystems, is presented in conceptual form, sufficient detail is included to permit an assessment of overall system performance and mass. Furthermore, an attempt is made to show how tailoring of the main subsystem design characteristics can be utilized to achieve synergistic system level advantages that can lead to improved reliability and enhanced system life while reducing the number of parasitic load driven peripheral subsystems.

Juhasz, Albert J.↗
NASA NTRS1991

Development of a Rayleigh scattering system for temperature measurements in combustor flows

A dual line laser induced Rayleigh scattering system has been developed to be used in high temperature gas flows such as in combustors, and preliminary tests have been performed in a hot air jet. The qualification measurements included the collection and analysis of Rayleigh signal for time-resolved gas temperature over the two lines of a copper-vapor laser. The dual line signal collection technique is a feature to be used in detecting and discriminating the surface scattered laser light in the Rayleigh signal. Optical fibers are used to transmit the laser beam to the optical probe bench and to carry the collected signal from the bench to the housing of the signal sensors. Incident laser intensity at the probe volume is measured for both lines at each pulse of the laser. This information is used to normalize the signal. Good agreement has been obtained between the two line Rayleigh scattering and thermocouple results in the particle free co-flowing air jet.

Otugen, M. V.↗