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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The distortion of the magnetotail equilibrium structure by a net cross-tail magnetic field

Explicit solutions are presented for quiet, quasi-static magnetotail configurations in the presence of a net cross-tail magnetic field component in addition to field components associated with tail flaring. The solutions are derived using the general three-dimensional equilibrium theory of Birn (1987). It is found that the net By(N) field varies only weakly along field lines and across the tail. The presence of the net By(N) in the neutral sheet implies that a part of the cross-tail current becomes field-aligned, flowing from the southern to the northern hemisphere for By(N) larger than zero and from north to south for By(n) less than zero. The deformations of magnetic flux surfaces suggest that there may be a class of field lines extending from the earth into the magnetosheath region through the low-latitude flanks of the tail. A topological connection is found of the low-latitude region near the magnetopause with the plasma sheet boundary layer, separating closed plasma sheet and open lobe field lines.

Birn, J.↗
NASA NTRS1992

Nonadiabatic heating of the central plasma sheet at substorm onset

Heating events in the plasma sheet boundary layer and central plasma sheet are found to occur at the onset of expansive phase activity. The main effect is a dramatic increase in plasma temperature, coincident with a partial dipolarization of the magnetic field. Fluxes of energetic particles increase without dispersion during these events which occur at all radial distances up to 23 RE, the apogee of the ISEE spacecraft. A major difference between these heating events and those observed at geosynchronous distances lies in the heating mechanism which is nonadiabatic beyond 10 RE but may be adiabatic closer to earth. The energy required to account for the increase in plasma thermal energy is comparable with that required for Joule heating of the ionosphere. The plasma sheet must be considered as a major sink in the energy balance of a substorm. Lobe magnetic pressures during these events are estimated. Change in lobe pressure are generally not correlated with onsets or intensifications of expansive phase activity.

Huang, C. Y.↗
NASA NTRS1981

Effects of plasma spray parameters on two layer thermal barrier

The power level and the type of arc gas used during plasma spraying of a two layer thermal barrier system (TBS) were found to affect the life of the system. Life at 1095 C in a cyclic furnace test was improved by about 140 percent by increasing the power during plasma spray applications of the bond and thermal barrier coatings. This improvement is due to increases in the densities of the bond and thermal barrier coatings by 3 and 5 percent, respectively. These increases in densities are equivalent to about 45 and 30 percent reduction in mean porosities, respectively. The addition of hydrogen to the argon arc gas had the same effect as the reduction in power level and caused a reduction in TBS life.

Stecura, S.↗
NASA NTRS1977

Substorm processes in the magnetotail - Comments on 'On hot tenuous plasmas, fireballs, and boundary layers in the earth's magnetotail' by L. A. Frank, K. L. Ackerson, and R. P. Lepping

Various theories regarding the magnetotail are reviewed and discussed. These include the work of Dungey (1961) and Eastman et al., (1976) regarding the generation of the magnetotail, Frank et al., (1976) concerning the so-called magnetotail fireball and its characteristics, and Hones et al., (1976 and 1976a) on the formation of a neutral line across the near-earth plasma sheet near the substorm onset. A detailed discussion of a fireball encounter during 0900-1400 UT in April 1974 is presented, noting plasma and magnetic phenomena observed, and magnetic records from the earth. A critique is made by Hones of the interpretation of this fireball made by Frank et al. In an accompanying reply, Frank et al. comment on the observations made by Hones, with attention to the most evident discrepancy between the two theories, i.e., the generation of large closed magnetic loops in the plasma sheet during magnetic substorms.

Hones, E. W., Jr.↗
DOE OSTI2020

Integrated modelling: Coupling of surface evolution and plasma-impurity transport

During the interaction of the scrape off layer (SOL) plasma with the first wall the evolution of both wall and plasma are tightly coupled: The erosion of the first wall leads to an impurity concentration in the plasma which affects the particle and power balance in the plasma. In turn the impurities, when leaving the plasma via transport, can form deposits and mixed materials, far away from their initial source location. These deposits can be eroded, allowing the impurities to stepwise migrate through the fusion device until they end up at a location where the plasma at the wall is cold enough and no further erosion occurs. To describe these processes an integrated model of surface evolution and plasma transport of impurities is needed. The WallDYN code achieves this required coupling of processes by parameterising the output of surface evolution- and plasma impurity-migration-codes by analytical models. For a given fixed background plasma it evolves the surface composition, derives impurity flux into and from the plasma and can from this derive the impurity densities in the plasma. This paper will show the importance of including this recycling of impurities at the wall in impurity migration modelling: The 13 CH 4 seeding experiment performed in the Wendelstein 7-X Stellerator is modelled using the recent extension of the WallDYN code to 3D plasma and wall geometries. A comparison with post mortem analysis of the 13 C deposition shows both qualitative and quantitative agreement with the WallDYN calculations.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Summary of NASA research on thermal-barrier coatings

A durable, two-layer, plasma-sprayed coating consisting of a ceramic layer over a metallic layer was developed that has the potential of insulating hot engine parts and thereby reducing metal temperatures and coolant flow requirements and/or permitting use of less costly and complex cooling configurations and materials. The investigations evaluated the reflective and insulative capability, microstructure, and durability of several coating materials on flat metal specimens, a combustor liner, and turbine vanes and blades. In addition, the effect on the aerodynamic performance of a coated turbine vane was measured. The tests were conducted in furnaces, cascades, hot-gas rigs, an engine combustor, and a research turbojet engine. Summaries of current research related to the coating and potential applications for the coating are included.

Stepka, F. S.↗
NASA NTRS1977

Summary of NASA research on thermal-barrier coatings

This paper summarizes the work conducted at the NASA Lewis Research Center to evolve and evaluate a two-layer, thermal-barrier coating system. A durable, two-layer, plasma-sprayed coating consisting of a ceramic layer over a metallic layer was developed that has the potential of insulating hot engine parts and thereby reducing metal temperatures and coolant flow requirements and/or permitting use of less costly and complex cooling configurations and materials. The investigations evaluated the reflective and insulative capability, microstructure, and durability of several coating materials on flat metal specimens, a combustor liner, and turbine vanes and blades. In addition, the effect on the aerodynamic performance of a coated turbine vane was measured. The tests were conducted in furnaces, cascades, hot-gas rigs, an engine combustor, and a research turbojet engine. Included also are summaries of current research related to the coating and potential applications for the coating.

Stepka, F. S.↗
NASA NTRS1978

NASA thermal barrier coatings: Summary and update

A durable, two-layer, plasma-sprayed coating consisting of a ceramic layer over a metallic layer was developed that has the potential of insulating hot engine parts and thereby reducing metal temperatures and coolant flow requirements and/or permitting use of less costly and complex cooling configurations and materials. The results are summarized of analytical and experimental investigations of the coatings on flat metal specimens, turbine vanes and blades, and combustor liners. Discussed are results of investigations to determine coating adherence and durability, coating thermal, strength and fatigue properties, and chemical reactions of the coating with oxides and sulfates. Also presented are the effect of the coating on aerodynamic performance of a turbine vane, measured vane and combustor liner temperatures with and without the coating, and predicted turbine metal temperatures and coolant flow reductions potentially possible with the coating. Included also are summaries of some current research related to the coating and potential applications for the coating.

Stepka, F. S.↗
NASA NTRS1978

NASA thermal barrier coatings - Summary and update

The work conducted at the NASA Lewis Research Center to evolve and evaluate a thermal-barrier coating system will be discussed. A durable, two-layer, plasma-sprayed coating consisting of a ceramic layer over a metallic layer was developed that has the potential of insulating hot engine parts and thereby reducing metal temperatures and coolant flow requirements and/or permitting use of less costly and complex cooling configurations and materials. The paper summarizes the results of analytical and experimental investigations of the coatings on flat metal specimens, turbine vanes and blades, and combustor liners. Discussed are results of investigations to determine coating adherence and durability, coating thermal, strength and fatigue properties, and chemical reactions of the coating with oxides and sulfates. Also presented are the effect of the coating on aerodynamic performance of a turbine vane, measured vane and combustor liner temperatures with and without the coating, and predicted turbine metal temperatures and coolant flow reductions potentially possible with the coating. Included also are summaries of some current research related to the coating and potential applications for the coating.

Stepka, F. S.↗
NASA NTRS1982

Transition from single to multiple double layers

Laboratory results are presented to define parameters which allow the boundary conditions to control the characteristics of double layers of plasma. It is shown that multiple double layers arise when the ratio of Debye length to system length decreases, a result which is in line with boundary layer theory. The significance of inclusion of the system length is noted to render BGK treatments of double layers, wherein the length is neglected, invalid.

Chan, C.↗
NASA NTRS1987

Some aspects of double layer formation in a plasma constrained by a magnetic mirror

The shift from wave-generated anomalous resistivity toward the more large-scale effects of magnetic confinement of current carrying plasmas was inspired by the more extensive data on auroral particle distribution functions that were made available, data that may often seem consistent with a dissipation-free acceleration of auroral electrons over an extended altitude range. Efforts to interpret these data have brought new vigor to the concept that a smooth and static electric field can be self-consistently generated by suitable pitch angle anisotropies among the high altitude particle populations, different for electrons and ions, and that such an electric field is both necessary and sufficient to maintain the plasma in a quasi-neutral steady state. Certain aspects of this concept are reviewed and criticized, both from a general theoretical standpoint and from the standpoint of what is known about the magnetospheric environment. It is argued that this concept has flaws and that the actual physical problem is considerably more complicated, requiring a more complex electric field, possibly including double layer structures.

Lennartsson, W.↗
NASA NTRS1986

Ceramic thermal barrier coatings for electric utility gas turbine engines

Research and development into thermal barrier coatings for electric utility gas turbine engines is reviewed critically. The type of coating systems developed for aircraft applications are found to be preferred for clear fuel electric utility applications. These coating systems consists of a layer of plasma sprayed zirconia-yttria ceramic over a layer of MCrAly bond coat. They are not recommended for use when molten salts are presented. Efforts to understand coating degradation in dirty environments and to develop corrosion resistant thermal barrier coatings are discussed.

Miller, R. A.↗
DOE OSTI2020

Method for forming perovskite layers using atmospheric pressure plasma

Improved deposition of optoelectronically active perovskite materials is provided with a two step process. In the first step, precursors are deposited on a substrate. In the second step, the deposited precursors are exposed to an atmospheric pressure plasma which efficiently cures the precursors to provide the desired perovskite thin film. The resulting films can have excellent optical properties combined with superior mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2021

2D measurements of parallel counter-streaming flows in the W7-X scrape-off layer for attached and detached plasmas

Abstract Investigations of particle parallel flow velocities have been carried out for the scrape-off layer (SOL) of the Wendelstein 7-X (W7-X) stellarator, in order to gain insights on the SOL transport properties during attached and detached plasma scenarios. The experimental evidence is based on the coherence imaging spectroscopy (CIS) diagnostic, able to measure 2D impurity emission intensity and flow velocity. The impurity monitored by CIS is C 2+ , characterized by a line-emission intensity observed to be linearly proportional to the total plasma radiated power in both attached and detached plasmas. The related C 2+ velocity shows a strong dependence on the line-averaged electron density while remaining insensitive to the input power. During attached plasmas, the velocity increases with increasing line-averaged density. The tendency reverses in the transition to and during detachment, in which the velocity decreases by at least a factor of 2. The sharp drop in velocity, together with a rise in line-emission intensity, is reliably correlated to the detachment transition and can therefore be used as one of its signatures. The impurity flow velocity appears to be well coupled with the main ions’ one, thus implying the dominant role of impurity-main ion friction in the parallelimpurity transport dynamics. In view of this SOL impurity transport regime, the CIS measurement results are here interpreted with the help of EMC3-Eirene simulations, and their major trends are already explainable with a simple 1D fluid model.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗