Hiroyuki Yamasaki

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

Characteristics of High Temperature Argon Heater in the Supersonic Closed Loop Experimental Facility for CCMHD Power Generation

We conduct one-dimensional numerical simulations on the thermal performance of a supersonic closed loop experimental facility for MHD power generation. In particular the thermal performance of a high temperature argon heater is investigated in detail. High-temperature (1900 K) argon gas is necessary for the MHD power generation. The variation of temperature and mass flow rate affect the inlet condition of the generator. The high temperature argon heater satisfies the required thermal performance by controlling the heater current in the case of an off-designed argon inflow.

Study on Fluid-Dynamical Performance of the Supersonic Closed Loop Experimental Facility

The closed loop experimental facility for closed-cycle magnetohydrodynamic (MHD) single power generation is now under construction at the Tokyo Institute of Technology. In this paper, we describe first experimental results from the closed loop facility using a linearshaped supersonic channel instead of a disk-shaped MHD power generator. The steady flow rate control by gas-flow ramp up and down and gas-charge and exhaust was successfully conducted. The pressure balance and the fluid-dynamical behavior in the closed loop were clarified by monitoring the time variations of pressure and temperature distributions. In particular, the characteristic frequency of the wall pressure in the supersonic channel was examined in detail.

Time Behavior of Impurities in the Supersonic Closed Loop Experimental Facility

Results of time dependent numerical simulation on the behavior of impurity concentrations in the closed loop facility are described. In the simulation, the closed loop was treated as the closed space with mass injection and ejection. As the purification methods, the pure argon charging, the discharge of contaminated argon and the evacuation of contaminated argon were considered. Furthermore, the effect of O2 removal system was included. The results suggest that the concentration of oxygen can be reduced down to the acceptable level by the considered purification method and that nitrogen concentration can be also decreased without using the N2 removal system. It is also found that the air leakage has a significant effect on the final O2 concentration achieved at the steady state. Effect of the initial residual air pressure on the final concentration of O2 is estimated to be small.

Experimental Results of Impurity Behavior in CLEF for CCMHD Power Generation

Experimental results of impurity behavior in the closed loop experimental facility (CLEF) are presented in this paper. The closed loop has been constracted to demonstrate an MHD power generation under a long duration time. In order to make the power generation successful, a molecular impurity level in a working gas of argon should be kept as low as possible. The present experimental results have shown that the procedure of replacing contaminated argon with pure argon is very useful to reduce impurity concentrations. At the same time, the results have shown a good performance of O2 removal system and of molecular sieve H2O removal system. Furthermore, it was found that the concentration of H2O decreased with an increase of ceramic temperature in the high temperature argon heater. It is suggested that the concentrations of H2O, N2 and O2 will be kept within a maximum permissible level for MHD power generation if the pressure inside the closed loop is kept higher than the atmospheric pressure.

Thermal Performances of Supersonic Closed Loop for Continuous MHD Power Generation

A closed loop experimental facility for continuous MHD power generation has been constructed at Tokyo Institute of Technology. A closed loop argon gas circulation including a heat recovery, an electrical gas heating, and a supersonic transition has been carried out for five days without MHD power generation. In this paper, streamwise profiles of an argon gas temperature and a pressure, an energy efficiency of a recuperator are examined. Thermal performances of a high temperature noble gas heater consisting of three electrical heaters are clarified. An argon gas peak temperature of 1317K is achieved by controlling input currents individually for three electrical heaters (7.65kA for a heater No.1, 6.67kA for a heater No.2, 5.60kA for a heater No.3) under conditions of the pressure of 0.253MPa and a flow rate of 500Nm/h (a mass flow rate of 0.248 kg/sec). The energy efficiency of the recuperator is 92%. The high-energy efficiency indicates efficient heat recovery performance of the recuperator.