Nonequilibrium Disk MHD Generator Research Articles

Numerical Study on the Effect of Anode Position on the Performance of Disk MHD Generator

The unsteady-state quasi-one-dimensional numerical simulations of the disk MHD generator have been conducted for various anode position. The results indicate that the non-equilibrium ionization instability of the plasma can be effectively suppressed by the appropriate anode position, and thus, the performance of the non-equilibrium disk MHD generator can be improved. Moreover, when the geometry and boundary conditions of disk MHD generator are determined, the optimal position of the anode is predicted to maximize the enthalpy extraction rate of the generator.

Numerical simulation of plasma and fluid behavior in the ISTEC-2 nonequilibrium disk MHD generator with multiple loads

Plasma and fluid behavior in a nonequilibrium disk magnetohydrodynamics generator with multiple loading has been investigated with a time-dependent three-dimensional numerical simulation. Particular attention is paid to the effects of the downstream load resistance and the influences of the middle electrode on the plasma and fluid flow. The possibility to improve generator performance by multiple-loading operation is also examined. It is shown that increase in the downstream load resistance raises the static pressure and decelerates the working gas in the upstream region. This is because the static pressure increase and the boundary layer development near the middle electrode have the same effects as the change of the outlet boundary conditions for the upstream region. It is found that the ionization degree of seed atoms is kept high on the middle electrode, whereas, the electron temperature is decreased rapidly. This results from the longer relaxation time of ion number density compared to that of the electron temperature. The multiple-loading operation leads to an improvement of the enthalpy extraction ratio. Isentropic efficiency, however, becomes somewhat lower under the multiple-loading condition. This is caused by the high static pressure and the low electrical efficiency under the high enthalpy extraction condition for the multiple loading.

Effect of load segmentation on the performance of a nonequilibrium disk MHD generator

Power generation experiments of a nonequilibrium disk MHD generator have been conducted under segmented load conditions. Effects of the load segmentation on the plasma fluid behavior and the generator performance are made clear. The MHD channel is divided into upstream and downstream parts. Although an MHD interaction along the fluid flow is divided by a middle electrode, each individual power generating part influences each other electrically and fluid dynamically. A higher loading condition in the upstream part is preferable in comparison with that in the downstream one to obtain higher electrical conductivity of the plasma. An excessive enthalpy extraction from the upstream part deteriorates the isentropic efficiency of the generator. It is possible for the segmented loading to maintain a comparable performance to that of the single-loading case by controlling each electrical efficiency in the segmented generation channels.

MHD Flow Behavior and Performance of Subsonic Non-equilibrium Disk MHD Generator Driven by Shock-tube Facility.

MHD flow behavior and the performance of an experimental nonequilibrium subsonic disk MHD generator driven by a shock-tube facility have been examined with time-dependent γ-z two-dimensional and γ-θ-z three-dimensional numerical simulations. In the subsonic MHD generator with two throats, the choking position is found to depend on the strength of MHD interaction. For optimal or high load operations, the flow chokes at the downstream throat and the subsonic flow is maintained in the generator channel. For low load operations, on the other hand, the flow chokes at the upstream throat and the flow becomes supersonic. In the generator under the subsonic flow condition, the relation between enthalpy extraction ratio and isentropic efficiency can be described as a function of Mach number at the anode for a fixed Mach number at the cathode. When the magnetic flux density is low, the inlet stagnation pressure should be decreased to achieve high enthaply extraction ratio and isentropic efficiency. The proper fluid flow and discharge structure can be realized under the optimal load resistance. Under the low resistance, however, shock-waves and ionization instability can occur and the generator performance can be deteriolated.

Effects of fluid flow on the performance of a subsonic nonequilibrium disk MHD generator

The fluid flow and performance of a nonequilibrium disk MHD generator with subsonic flow are examined by time-dependent two-dimensional r–z numerical simulations. It is found that the development of the boundary layer is enhanced with increasing load resistance, as is the case in supersonic generators. The development of the boundary layer affects not only the performance of the generator but the thermal input to it, in contrast to supersonic generators. These facts lead to considerable departures from the performance predicted by a quasi-one-dimensional simulation and suggest that two-dimensional design of the generator channel, taking account of boundary layer development, is necessary in order to assure high performance of a subsonic generator. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 18–25, 2000

超音速非平衡ディスク形MHD発電機の動作特性に及ぼす

超音速非平衡ディスク形MHD発電機の動作特性に及ぼす

Operation and control of coupled nonequilibrium disk MHD generator and inverter system under power line fault condition

Operation and control of coupled nonequilibrium disk MHD generator and inverter system under power line fault condition

Plasma behavior in a non-equilibrium disk MHD generator with a spatially non-uniform seed fraction

The influence of azimuthal non-uniformity of the seed fraction on plasma structure and performance in a non-equilibrium disk MHD generator is investigated with a two dimensional r–θ numerical simulation. It is found that a locally high seed fraction causes mainly non-uniformity of gas-dynamical properties, whereas a locally low seed fraction develops a non-uniform plasma. Both locally high and low seed fractions reduce generator performance considerably. These results suggest a spatially uniform seed fraction should be required for high power generation. ©1999 Scripta Technica, Electr Eng Jpn, 126(4): 48–54, 1999

熱入力100MW非平衡ディスク形MHD発電機におけるプラズマ・流体の三次元構造

熱入力100MW非平衡ディスク形MHD発電機におけるプラズマ・流体の三次元構造

入ロスワールをもつ非平衡ディスク形MHD発電機内プラズマ・流体の三次元構造

入ロスワールをもつ非平衡ディスク形MHD発電機内プラズマ・流体の三次元構造

亜音速平衡ディスク形MHD発電機内の流れと発電性能

亜音速平衡ディスク形MHD発電機内の流れと発電性能

非平衡ディスク形MHD発電機における放電構造と発電性能に及ぼす背圧の影響

非平衡ディスク形MHD発電機における放電構造と発電性能に及ぼす背圧の影響

非平衡ディスク形MHD発電機における高周波予備電離を用いた性能改善

非平衡ディスク形MHD発電機における高周波予備電離を用いた性能改善

非平衡ディスク形MHD発電機・インバータシステムの系統故障時の運転・制御

非平衡ディスク形MHD発電機・インバータシステムの系統故障時の運転・制御

熱入力100 MW Ar-Gs非平衡ディスク形MHD発電機の系統連系時の動作特性の検討

熱入力100 MW Ar-Gs非平衡ディスク形MHD発電機の系統連系時の動作特性の検討

Electron temperature measurement and performance of a nonequilibrium disk MHD generator

Electron temperature measurement and performance of a nonequilibrium disk MHD generator

空間的なシード不均一下での非平衡ディスク形MHD発電機内プラズマの挙動

空間的なシード不均一下での非平衡ディスク形MHD発電機内プラズマの挙動

Conceptual design of coupled nonequilibrium disk MHD generator and superconducting magnet system

The authors propose a new conceptual design method for a coupled nonequilibrium disk MHD generator and superconducting magnet system. At first, a generator with constant magnetic flux density is conceptually designed by using the new generator design method recently developed by the authors, and several superconducting magnets suitable for the generator are conceptually designed. Next, considering the obtained magnetic flux density distribution of each magnet, the design calculation of the generator is performed again, and the specifications of the generator are corrected. From the obtained coupled systems, the optimum system is finally selected through synthetical consideration of various requirements. The procedure of the proposed method is very simple, and no iterative calculation is contained in the correction process. Incorporating the new generator design method makes this advantage possible because the generator size can be fixed in the correction process. In the conventional method, a change of magnetic flux density distribution leads directly to a change in the generator size, and therefore, design calculations of the generator and magnet should be iterated in the correction process until they converge to consistent sizes. The procedure of the new conceptual design method is explained in detail by taking the case of a supersonic generator with a caesium seeded helium plasma and 100 MW thermal input.

Measurements of properties concerning isentropic efficiency in a nonequilibrium MHD disk generator

The isentropic efficiency and the effective Hall parameter in a nonequilibrium disk MHD generator have been successfully evaluated on the basis of the experiments under high enthalpy extraction conditions. Special attention is devoted to measuring the exit total pressure and the Faraday current. The maximum isentropic efficiency achieved in the present experiments was 46% with the enthalpy extraction ratio of 31.6%. The experimentally obtained values of the effective Hall parameter covered a range of 2-3.

Characteristics of flow and plasma under high MHD interaction in nonequilibrium disk MHD generator using argon

AbstractResults of experimental studies on behavior of a supersonic flow and of a nonequilibrium plasma in a disk MHD generator are presented. The experiments with cesium seeded argon were carried out under high MHD interaction conditions. Effects of seed fractions on static pressure distributions, flow Mach numbers, electron temperatures and uniformity of discharge in the disk MHD channel were investigated. The results have shown that the flow is kept supersonic throughout the disk MHD channel when a sufficient Joule heating exists in a supersonic nozzle and the seed is fully ionized. It was found that there was an optimum seed fraction at which the power output became maximum and, at the same time, the seed was fully ionized. Furthermore, an almost uniform discharge due to the full ionization of seed was observed. It is noted that enthalpy extractions and adiabatic efficiencies were increased remarkably, and the highest enthalpy extraction of 26.5 percent was achieved for cesium seeded argon. However, adiabatic efficiencies remained still low due to large pressure losses.