Search NASA⌕ Search

SEARCH · Search NASA

Results for “MHD”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

A summary of the ECAS performance and cost results for MHD systems

The potential is examined of various advanced power plant concepts using coal and coal-derived fuel. The results indicate that open cycle coal fired direct preheat MHD systems have potentially one of the highest coal-pile-to-bus-bar efficiencies and also one of the lowest costs of electricity (COE) of the systems studied. Closed cycle MHD systems may have the potential to approach the efficiency and COE of open cycle MHD. The 1200-1500 F liquid metal MHD systems studied do not appear to have the potential of exceeding the efficiency or competing with the COE of advanced steam plants.

Seikel, G. R.↗
NASA NTRS1976

A summary of the ECAS performance and cost results for MHD system

The interagency-funded, NASA-coordinated Energy Conversion Alternatives Study (ECAS) has studied the potential of various advanced power plant concepts using coal and coal-derived fuel. Principle studies were conducted through prime contracts with the General Electric Company and the Westinghouse Electric Corporation. The results indicate that open-cycle coal-fired direct-preheat MHD systems have potentially one of the highest coal-pile-to-bus-bar efficiencies and also one of the lowest costs of electricity (COE) of the systems studied. Closed-cycle MHD systems may have the potential to approach the efficiency and COE of open-cycle MHD. The 1200-1500 F liquid-metal MHD systems studied do not appear to have the potential of exceeding the efficiency or competing with the COE of advanced steam plants.

Seikel, G. R.↗
NASA NTRS1980

Rapporteur report: MHD electric power plants

Five US papers from the Proceedings of the Seventh International Conference on MHD Electrical Power Generation at the Massachusetts Institute of Technology are summarized. Results of the initial parametric phase of the US effort on the study of potential early commercial MHD plants are reported and aspects of the smaller commercial prototype plant termed the Engineering Test Facility are discussed. The alternative of using a disk geometry generator rather than a linear generator in baseload MHD plants is examined. Closed-cycle as well as open-cycle MHD plants are considered.

Seikel, G. R.↗
NASA NTRS1980

Disk MHD generator study

Directly-fired, separately-fired, and oxygen-augmented MHD power plants incorporating a disk geometry for the MHD generator were studied. The base parameters defined for four near-optimum-performance MHD steam power systems of various types are presented. The finally selected systems consisted of (1) two directly fired cases, one at 1920 K (2996F) preheat and the other at 1650 K (2500 F) preheat, (2) a separately-fired case where the air is preheated to the same level as the higher temperature directly-fired cases, and (3) an oxygen augmented case with the same generator inlet temperature of 2839 (4650F) as the high temperature directly-fired and separately-fired cases. Supersonic Mach numbers at the generator inlet, gas inlet swirl, and constant Hall field operation were specified based on disk generator optimization. System pressures were based on optimization of MHD net power. Supercritical reheat stream plants were used in all cases. Open and closed cycle component costs are summarized and compared.

Retallick, F. D.↗
NASA NTRS1981

A MHD channel study for the ETF conceptual design

The procedures and computations used to identify an MHD channel for a 540 mW(I) EFT-scale plant are presented. Under the assumed constraints of maximum E(x), E(y), J(y) and Beta; results show the best plant performance is obtained for active length, L is approximately 12 M, whereas in the initial ETF studies, L is approximately 16 M. As MHD channel length is reduced from 16 M, the channel enthalpy extraction falls off, slowly. This tends to reduce the MHD power output; however, the shorter channels result in lower heat losses to the MHD channel cooling water which allows for the incorporation of more low pressure boiler feedwater heaters into the system and an increase in steam plant efficiency. The net result of these changes is a net increase in the over all MHD/steam plant efficiency. In addition to the sensitivity of various channel parameters, the trade-offs between the level of oxygen enrichment and the electrical stress on the channel are also discussed.

Wang, S. Y.↗
NASA NTRS1982

Summary and evaluation of the conceptual design study of a potential early commercial MHD power plant (CSPEC)

The conceptual design study of a potential early commercial MHD power plant (CSPEC) is described and the results are summarized. Each of two contractors did a conceptual design of an approximtely 1000 MWe open-cycle MHD/steam plant with oxygen enriched combustion air preheated to an intermediate temperatue in a metallic heat exchanger. The contractors were close in their overall plant efficiency estimates but differed in their capital cost and cost of electricity estimates, primarily because of differences in balance-of-plant material, contingency, and operating and maintenance cost estimates. One contractor concluded that its MHD plant design compared favorably in cost of electricity with conventional coal-fired steam plants. The other contractor is making such a comparison as part of a follow-on study. Each contractor did a preliminary investigation of part-load performance and plant availability. The results of NASA studies investigating the effect of plant size and oxidizer preheat temperature on the performance of CSPEC-type MHD plants are also described. The efficiency of a 1000 MWe plant is about three points higher than of a 200 MWe plant. Preheating to 1600 F gives an efficiency about one and one-half points higher than preheating to 800 F for all plant sizes. For each plant size and preheat temperature there is an oxidizer enrichment level and MHD generator length that gives the highest plant efficiency.

Staiger, P. J.↗
NASA NTRS1982

Radiation-driven MHD systems for space applications

High-power radiation such as concentrated solar or high-power laser radiation is considered as a driver for magnetohydrodynamic (MHD) systems which could be developed for efficient power generation and propulsion in space. Eight different systems are conceivable since the MHD systems can be classified in two: plasma and liquid-metal MHD's. Each of these systems is reviewed and solar- (or laser-) driven MHD thrusters are proposed.

Lee, J. H.↗
NASA NTRS1981

Parametric study of potential early commercial MHD power plants. Task 3: Parameter variation of plant size

Plants with a nominal output of 200 and 500 MWe and conforming to the same design configuration as the Task II plant were investigated. This information is intended to permit an assessment of the competitiveness of first generation MHD/steam plants with conventional steam plants over the range of 200 to 1000 MWe. The results show that net plant efficiency of the MHD plant is significantly higher than a conventional steam plant of corresponding size. The cost of electricity is also less for the MHD plant over the entire plant size range. As expected, the cost differential is higher for the larger plant and decreases with plant size. Even at the 200 MWe capacity, however, the differential in COE between the MHD plant and the conventional plant is sufficient attractive to warrant serious consideration. Escalating fuel costs will enhance the competitive position of MHD plants because they can utilize the fuel more efficiently than conventional steam plants.

Hals, F. A.↗
NASA NTRS1984

MHD stability of compressible coronal loops with radiative energy loss

The effect of radiative energy loss on the stability of compressible plasma in coronal loops is studied. By taking the limit as poloidal wavenumber m approaches infinity, stability conditions for local modes are derived. It was found that the radiation effect can trigger MHD instabilities of coronal loops which are in ideally marginally stable states. Compressibility is a stabilizing effect for ideal MHD local modes because the compression of magnetic field lines exerts a restoring force by increasing magnetic pressure. Compression of plasma induces two modes in a radiatively unstable plasma, magnetosonic and condensation modes. Compressibility affects the stability of ideally stable (or unstable) coronal plasmas through magnetosonic modes, which are a stabilizing (destabilizing) effect for ideally stable (unstable) plasmas. For coronal plasmas in ideally marginally stable states, condensation as well as magnetosonic modes can trigger MHD instability. Because of these two modes, the effect of radiation on compressible coronal plasmas is more destabilizing than it is on incompressible plasmas when the plasmas are in ideal MHD unstable or marginally stable states.

An, C.-H.↗
NASA NTRS1984

Analytical estimates of turbulent MHD transport coefficients

Turbulent transfer rates from small-scale MHD excitations to large-scale Fourier modes are calculated algebraically, using the method of Biskamp and Welter. Three cases are considered: two-dimensional Navier-Stokes flows, two-dimensional incompressible MHD, and the weakly three-dimensional Strauss equations. In all cases, an initially large spectral gap between the small-scale and large-scale excitations is assumed, and attention focusses on the initial values of the back-transfer rates. The sign of the transfer is determined by the sign of an analytically calculable eddy viscosity and/or anomalous resistivity. We are able to confirm the results of Biskamp and Welter for the case of two-dimensional MHD, but find some differences for the case of the Strauss equations. It is argued that the Strauss equations may not exhibit an inverse cascade phenomenon for the spatially periodic case unless their initial spectra are such that the behavior is essentially that of two-dimensional MHD.

Montgomery, D.↗
NASA NTRS1983

Parametric study of potential early commercial power plants Task 3-A MHD cost analysis

The development of costs for an MHD Power Plant and the comparison of these costs to a conventional coal fired power plant are reported. The program is divided into three activities: (1) code of accounts review; (2) MHD pulverized coal power plant cost comparison; (3) operating and maintenance cost estimates. The scope of each NASA code of account item was defined to assure that the recently completed Task 3 capital cost estimates are consistent with the code of account scope. Improvement confidence in MHD plant capital cost estimates by identifying comparability with conventional pulverized coal fired (PCF) power plant systems is undertaken. The basis for estimating the MHD plant operating and maintenance costs of electricity is verified.

Source record↗
NASA NTRS1984

The effect of line-tying on the radiative MHD stability of coronal plasmas with radial pressure profile

The role of photospheric line-tying, i.e., solar coronal loop structures, was investigated in terms of the effect on radiative modes and the influence that different radial pressure profiles exert on the effects of line-tying on radiative MHD stability. Energy is assumed dissipated by heat conduction and radiation and zero- and first-order solutions are obtained for the radiative time scales. Line-tying is a magnetic tension in the zero-order MHD mode and produces stability. Heat conduction occurs along bent field lines in first-order MHD modes when plasmas cross the field lines. Irradiated cool-core loops can experience MHD instabilities in the cylinder center, while line-tying can stabilize the plasma in the surrounding hot medium. Line-tying also adds stability to magnetosonic and condensation modes.

An, C.-H.↗
NASA NTRS1986

Laser-powered MHD generators for space application

Magnetohydrodynamic (MHD) energy conversion systems of the pulsed laser-supported detonation (LSD) wave, plasma MHD, and liquid-metal MHD (LMMHD) types are assessed for their potential as space-based laser-to-electrical power converters. These systems offer several advantages as energy converters relative to the present chemical, nuclear, and solar devices, including high conversion efficiency, simple design, high-temperature operation, high power density, and high reliability. Of these systems, the Brayton cycle liquid-metal MHD system appears to be the most attractive. The LMMHD technology base is well established for terrestrial applications, particularly with regard to the generator, mixer, and other system components. However, further research is required to extend this technology base to space applications and to establish the technology required to couple the laser energy into the system most efficiently. Continued research on each of the three system types is recommended.

Jalufka, N. W.↗
NASA NTRS1988

An observational study of MHD wave-induced density fluctuations upstream of the earth's bow shock

An investigation of plasma density fluctations upstream of the earth's bow shock and their association with MHD waves is reported. The normalized density fluctuation was 14 percent on a day when the plasma beta was less than unity and the waves were circularly polarized and of relatively low amplitude, and 17 percent on a day when the plasma beta was in excess of unity and the waves were elliptically polarized and of large fractional amplitude. On both days there was a feature of the density power spectrum at the MHD carrier wave frequency attributable to oblique propagation of the waves with propagation angles of a few degrees with respect to the mean field. Ponderomotive effects due to spatial gradient in the MHD wave energy density are proposed as responsible for a correlation betweeen density and transverse wave intensity on both days. Generation of density fluctuations by linear polarized MHD waves is not an important contributor to the observed density fluctuations.

Spangler, Steven↗
NASA NTRS1988

MHD turbulent processes

Three areas of study in MHD turbulence are considered. These are the turbulent relaxation of the toroidal Z pinch, density fluctuations in MHD fluids, and MHD cellular automata. A Boolean computer game that updates a cellular representation in parallel and that has macroscopic averages converging to solutions of the two-dimensional MHD equations is discussed.

Montgomery, David↗
NASA NTRS1991

Oblique MHD cosmic-ray modified shocks: Two-fluid numerical simulations

We present the first results of time dependent, two-fluid, cosmic-ray (CR) modified, MHD shock simulations. The calculations were carried out with a new numerical code for 1-D ideal MHD. By coupling this code with the CR energy transport equation we can simulate the time-dependent evolution of MHD shocks including the acceleration of the CR and their feedback on the shock structures. We report tests of the combined numerical method including comparisons with analytical steady state results published earlier by Webb, as well as internal consistency checks for more general MHD CR shock structures after they appear to have converged to dynamical steady states. We also present results from an initial time dependent simulation which extend the parameter space domain of previous analytical models. These new results support Webb's suggestion that equilibrium oblique shocks are less effective than parallel shocks in the acceleration of CR. However, for realistic models of anisotropic CR diffusion, oblique shocks may achieve dynamical equilibrium on shorter timescale than parallel shocks.

Frank, Adam↗
NASA NTRS1993

A numerical implementation of MHD in divergence form

Shock computations are presently undertaken by a numerical implementation of fully relativistic MHD in divergence form, as illustrated by pseudospectral-method computations for the coplanar Riemann MHD problem. Compound waves are noted to persist in relativistic MHD. Attention is given to two limiting cases: (1) where the velocities become nonrelativistic, and (2) where the longitudinal magnetic field becomes zero. Comparisons are made with results for both the singular case of zero longitudinal magnetic field, and nonrelativistic MHD.

Van Putten, Maurice H. P. M.↗
NASA NTRS1993

Numerical study of 1-D, 3-vector component, thermally-conductive MHD solar wind

In the present study, transient, 1-dimensional, 3-vector component MHD equations are used to simulate steady and unsteady, thermally conductive MHD solar wind expansions between the solar surface and 1 AU (astronomical unit). A variant of SIMPLE numerical method was used to integrate the equations. Steady state solar wind properties exhibit qualitatively similar behavior with the known Weber-Davies Solutions. Generation of Alfven shock, in addition to the slow and fast MHD shocks, was attempted by the boundary perturbations at the solar surface. Property changes through the disturbance were positively correlated with the fast and slow MHD shocks. Alfven shock was, however, not present in the present simulations.

Han, S.↗