Numerical Simulation on Performance of Disk MHD Generator in the Closed-Loop Experimental Facility

A time dependent two-dimensional numerical simulation has been carried out in order to clarify the magnetohydrodynamic (MHD) flow behavior and performance of a disk MHD generator installed in a new closed-loop experimental facility at the Tokyo Institute of Technology. The numerical investigation is not limited to the generator channel only, but also includes an inlet duct and a downstream 90deg-bend diffuser. A set of possible generator inlet-outlet pressure ratio (PR) was selected, and the influence on flow physics and generator performance was examined. Maximum enthalpy extraction (EE) ratio was obtained at high PR. In this case, an oblique shock wave appeared in the 90deg-bend diffuser for both non-MHD and MHD flow regimes. The EE, however, did not vary monotonically with the PR. Rather a local minimum point for the EE was observed at moderate PR. In this case, either an oblique shock wave or a normal shock wave would appear in the generator channel depending upon whether the flow was in the non-MHD or MHD regime. The results predicted in the present simulation are valuable and important for setting the working gas conditions and evaluating generator performance in the closed-loop power generation experiment

I. Introduction

For several years, the closed-cycle magnetohydrodynamic (CCMHD) power generator, using nonequilibrium plasma, has been seen as a potential new energy conversion device [1], [2]. The CCMHD generator directly converts the enthalpy of a high-temperature gas (2000 K) to electrical energy without the utilization of any rotating parts, offering better energy conversions than conventional devices.