Effect of Nozzle Load Resistance and Stagnation Gas Pressure on Performance of Disk MHD Generator with Small Area Ratio

Abstract

SUMMARYAn experimental study on performance of a disk MHD generator was carried out using a shock-tube driven facility. Effects of nozzle load resistance and stagnation gas pressure on the enthalpy extraction, the total pressure ratio, and the adiabatic efficiency were investigated for a disk MHD generator with a small area ratio. The enthalpy extraction and the adiabatic efficiency were found to be affected by the nozzle load resistance. The results suggest that the nozzle load resistance should be kept high for high performance of the disk MHD generator with small area ratio. Furthermore, an increase of stagnation pressure resulted in a slight increase of enthalpy extraction. However, the increase of stagnation pressure led to a remarkable increase of adiabatic efficiency. The increase of the adiabatic efficiency was due to an increase of the total pressure ratio. The effects of the electrical efficiency, the Mach number, and loss parameters for heat and friction on the total pressure ratio are discussed. The discussion suggests that the increase of total pressure ratio is due to a relative decrease of pressure loss due to wall friction. In addition, the highest adiabatic efficiency for cesium-seeded argon was achieved in the present experiment without the introduction of inlet swirl. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 3746, 2001

Experiments and numerical simulations on high-density magnetohydrodynamic electrical power generation

“…In previous shock-tube-driven power-generating experiments, large-scale MHD generators ͑MHD power-generating channel length and volume are 160 mm and 4.2ϫ 10 −3 m 3 , respectively͒ have been used. [19][20][21][22][23][24][25][26][27][28] In contrast, the present generator has a small-scale power-generating volume, that is 1 / 6 those of previous generators. Generally, the electrical power output tends to depend on L ch B 2 ṁ ͑L ch is the MHD channel length, B is the magnetic flux density, and ṁ is the mass flow rate͒.…”

An analytical study of the plasma conditions and performance of an MHD generator

“…(1)] and the energy loss by collisions [Eq. (2)] are in balance, electron energy equation (1) or (2) can be solved analytically for the electron temperature.…”

“…The effect of an elastic collision is considered in Eq. (2), where the gas (heavy particle) temperature is assumed to be constant because the variation in the gas temperature is negligible in comparison with that in the electron temperature. Since the plasma behavior in the main flow region of the MHD generator is focused, energy flow to walls of the generator is not taken into account.…”

“…It has been stated that the relationship between the enthalpy extraction ratio and isentropic efficiency depends on the cross-sectional area ratio and the Mach number at the exit of the generator. The effects of stagnation pressure on the performance have also been examined in order to elucidate the fluid-dynamical features of the disk MHD generator [2].In the present work, local steady-state analytical calculations are conducted to investigate the effect of plasma conditions on the performance of the MHD generator, taking the linear theory of ionization instability into account. It is well known that ionization instability results in nonuniformity of the plasma, thus degrading power generation performance.…”

“…It is well known that ionization instability results in nonuniformity of the plasma, thus degrading power generation performance. Although fluid-dynamical investigation of the performance has been conducted, the effect of the behavior of the nonequilibrium MHD seed plasma has never been considered in previous investigations [1,2]. The present study is based on a simple analytical calculation rather than a numerical simulation, solving differential equations to improve the analytical study.…”