Subsonic MHD Generator Research Articles

Numerical simulation on operation of closed‐loop experimental facility with subsonic MHD generator

AbstractThe operating characteristics and operation procedure of the closed‐loop experimental facility under subsonic power generation have been investigated by means of time‐dependent quasi‐one‐dimensional numerical simulations. Two ways of operation for subsonic power generation were found: (1) subsonic operation both under nonpower and power generation and (2) supersonic operation under nonpower generation and subsonic operation under power generation. For operation (1), Mach number at channel inlet decreases to ∼0.6, therefore it is required to generate plasma under this Mach number. On the other hand, if the plasma cannot be generated, operation (2) needs to be carried out. In this case, a shock wave appears in the generator channel, then the influence of a large pressure change and a vibration caused by a shock wave in the generator channel needs to be considered. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 25–33, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20399

Numerical Simulation on Operation of Closed Loop Experimental Facility with Subsonic MHD Generator

The operating characteristics and operation procedure of the closed loop experimental facility under subsonic power generation have been investigated by means of time-dependent quasi-one-dimensional numerical simulations. It was found that there are two ways of operation for the subsonic power generation, which are (1)a subsonic operation both under non-power and power generation and (2)a supersonic operation under non-power generation and subsonic operation under power generation. For the operation(1), Mach number at channel inlet decreases to ˜0.6, therefore it is required to generate plasma under this Mach number. On the other hand, if the plasma cannot be generated, the operation(2) needs to be carried out. In this case, a shock wave appears in the generator channel, then the influence of a large pressure change and a vibration caused by a shock wave in the generator channel needs to be considered.

MHD flow simulation in subsonic disk MHD generator driven by a shock tube facility

AbstractThe 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 r−z two‐dimensional and r−θ−z three‐dimensional Large Eddy Simulation for the first time. The calculation region is extended and covers a hot duct through a downstream duct including the subsonic MHD generator with two throats. For optimal and high load operations, the flow chokes at the downstream throat and the subsonic flow is maintained in the generator channel. The discharge structure is uniform in the θ direction, and suitable fluid flow is realized in the generator channel, although the large boundary layer separations and eddies are observed behind the downstream throat. For low load operations, the flow chokes at the upstream throat and the flow becomes supersonic, where pseudo‐shock waves and large eddies are observed in the generator channel and the downstream duct. The ionization instability in the r−θ plane occurs in the generator channel, which deteriorates the generator performance. Asymmetric flow at the generator inlet, which is attributed to the change of flow direction from the hot duct, seems not to be significant for the generator performance. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 1–8, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10130

衝撃波管駆動亜音速非平衡ディスク形MHD発電機内の電磁流体シミュレーション

The 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 r−z two-dimensional and r−θ−z three-dimensional Large Eddy Simulation for the first time. The calculation region is extended and covers a hot duct through a downstream duct including the subsonic MHD generator with two throats. For optimal and high load operations, the flow chokes at the downstream throat and the subsonic flow is maintained in the generator channel. The discharge structure is uniform in the θ direction, and suitable fluid flow is realized in the generator channel, although the large boundary layer separations and eddies are observed behind the downstream throat. For low load operations, the flow chokes at the upstream throat and the flow becomes supersonic, where pseudo-shock waves and large eddies are observed in the generator channel and the downstream duct. The ionization instability in the r−θ plane occurs in the generator channel, which deteriorates the generator performance. Asymmetric flow at the generator inlet, which is attributed to the change of flow direction from the hot duct, seems not to be significant for the generator performance. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 1–8, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10130

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.

Transient Characteristics of Constant Velocity Faraday-Type MHD Generator

Transient characteristics of an open-cycle constant velocity Faraday-type MHD generator comparable to the size of Russian U·25 (MHD Experimental Generator at the Institute for High Temperatures, Moscow) are presented. Transient responses to start-up, shutdown and load changes of a subsonic MHD generator are numerically calculated solving unsteady magnetohydrodynamic equations. Results show that the MHD generator can attain another steady state within ten times the gas residence time for most of load changes. When loads locally change, shock waves occur to cause considerable fluid property change. The most dangerous transient characteristics are due to very large transient Hall fields at the start-up, which leads to breakdown between adjacent electrodes, particularly, the down-stream region of the generator. For local short-circuiting or load changes throughout the generator, no serious problems arise except for those associated with current density increase.

Transient Characteristics of Constant Velocity Faraday-Type MHD Generator

Transient characteristics of an open-cycle constant velocity Faraday-type MHD generator comparable to the size of Russian U·25 (MHD Experimental Generator at the Institute for High Temperatures, Moscow) are presented. Transient responses to start-up, shutdown and load changes of a subsonic MHD generator are numerically calculated solving unsteady magnetohydrodynamic equations. Results show that the MHD generator can attain another steady state within ten times the gas residence time for most of load changes. When loads locally change, shock waves occur to cause considerable fluid property change. The most dangerous transient characteristics are due to very large transient Hall fields at the start-up, which leads to breakdown between adjacent electrodes, particularly, the down-stream region of the generator. For local short-circuiting or load changes throughout the generator, no serious problems arise except for those associated with current density increase.

Voltage-current characteristics of the electrode boundary layer in a thermally nonequilibrium dense plasma

The contact between a thermally nonequilibrium dense plasma and the emitter electrode in a subsonic MHD generator channel is considered. Only the three-particle recombination reaction is treated, in the absence of any magnetic field. The electrode layer is divided into two regions — quasineutral and space-charge areas. The equations which describe the electrophysical processes in these regions are solved numerically on a BESM-6 computer. The results are presented in the form of voltage-current curves for the electrode boundary layer at various temperature values for the wall, main flow, and electrons.