Nobuhiro Harada

High enthalpy extraction from a helium-driven disk magnetohydrodynamic generator

A power-generation experiment with a disk MHD generator driven by potassium-seeded helium was made. High values of the output power density and of the enthalpy extraction have been obtained. For helium temperatures between 2200 and 2400 K, an output power density of 120 MW/cu m and an enthalpy extraction of 20.4 percent have been measured. The measured static pressure distribution has shown that strong gasdynamical shock has not been observed in the MHD channel under this high enthalpy extraction. It has been suggested that the disk generator performances can be predicted by one-dimensional calculations with ideal plasma parameters for the case of no negative potential region at the channel inlet and no shock formation in the disk generator. 11 refs.

Observations of nonequilibrium electrical discharge in an MHD disk generator

Discharge phenomena (nonequilibrium) in an MHD disk generator with potassium-seeded argon as a working gas have been investigated experimentally using a shock tube facility. A detailed study of high-speed photographs shows that an unsteady motion of a strongly constricted discharge occurs, particularly in the disk entrance region, characterized by a negative Hall potential. Responding to a suitable external load resistance, the negative Hall potential is reduced due to the development of a stable region against the ionization instability under full seed ionization; thus, a substantial increase of power output can be achieved. Under this condition, a uniform discharge is observed downstream and the strongly inhomogeneous and unsteady discharge is confined to a narrow region at the entrance. For smaller load resistances, intense spiral arcs with enhanced fluctuations are observed. 18 references.

Numerical simulation studies on FUJI-1 experiments

Abstract Experimental results of the FUJI-1 disk generator have been discussed from the calculated results based on the quasi-one-dimensional model. The calculations have been performed for generators with different channel shape to investigate the effects of the area ratio on power generation performance. The increase of output power at the high load resistance regime with increase of area ratio has been qualitatively shown by calculations, however absolute values of the plasma properties in an MHD channel obtained from the calculations have not been in agreement with experiment values. To clarify the pressure loss mechanism, the influences of the plasma properties on the changes of stagnation pressure have been investigated analytically. It has been found that the strong Lorentz force takes a significant role in the pressure loss processes as compared with wall friction under a strong MHD interaction conditions. Furthermore, it has been suggested that a 100 MW class thermal input generator is required to reduce the stagnation pressure loss by wall friction with high gas velocity and high output power.

Studies on Capacitor Coupled Power Extraction from an MHD generator

To avoid the damage of the electrodes, the capacitor coupled MHD generator has been proposed. Because the capacitor coupled MHD generator relies on the conventional MHD generator, the method of generating electromotive force is almost same without the extraction of electric power. To obtain the same output power of the conventional MHD generator, the capacitor coupled MHD generator is required to be higher AC magnetic field frequency or the larger capacitance of the channel. To demonstrate the capacitor coupled MHD generator, the transient MHD generator based on the model rocket engine was constructed. We can see that the capacitor coupled MHD generator extracts the electric energy. To understand the noise from the preionization discharge, we compared the capacitor coupled MHD generator with applied magnetic field to that without applied magnetic field. The result indicates that the extraction of electromotive force is not observed the capacitor coupled MHD generator without applied magnetic field.

Carbon Dioxide Emission Free Power Generation System

Cpo = specific heat of oxygen at constant pressure Tin = inlet temperature of oxygen compressor Tout = outlet temperature of oxygen compressor Pin = inlet pressure of oxygen compressor Pout = outlet pressure of oxygen compressor ṁo = mass flow rate of oxygen Qeo2 = electric power of oxygen compressors h1 = inlet enthalpy of CO2 compressors h2 = outlet enthalpy of CO2 compressors Qeco2 = electric power of CO2 compressors Qin = combution energy of methane Cp = specific heat of combustion gas at constant pressure γo = adiabatic constant of oxygen ηa = adiavatic efficiency of compressors ηc = mechanical efficiency of compressors

Ionization relaxation region in a nonequilibrium disk MHD generator

The ionization relaxation region in an Ar/K-driven disk MHD generator and its effects have been experimentally investigated. Experimental results have shown that a decrease in the stagnation temperature of a working gas increases the area covered by the negative Hall field near the anode, which is strongly affected by ionization relaxation, and results in reducing output power. It is also observed that the power output increases with an increase in seed fraction. The unfavorable effects of ionization relaxation can be reduced by increasing applied magnetic field strength. Comparison between the results of one-dimension al calculations and experimental results has also been performed. Calculations can predict the Hall potential distribution along the flow direction when we assume an adequate electron temperature at the MHD channel inlet and fluctuations of a plasma at the inlet of the channel are assumed to be insignificant.

Interaction of a Plasma Stream with Neutral Gases under an Aligned Magnetic Field

Relaxation of a stationarily flowing jet-like plasma, which penetrates into a neutral gas with temperature and kinetic energy much lower than the ionization potential, is investigated experimentally by measuring spatial distributions of hydrodynamic quantities such as plasma flow velocity, electron temperature and density in the plasma-neutral gas interaction zone. The experimental results agree with calculations. The particle, momentum and energy conservations of the plasma in the interaction zone are dominated by diffusion, ion elastic collision with neutral atoms and ionization, respectively.

Study on Specific Mass of Nuclear Electric Propulsion System with Closed Cycle MHD Generator

In space, radiation dose to crew increases in proportion to a increase of flight-time. High radiation dose to human have an influence on human health. Therefore, propulsion system that can minimize in-flight time is required. In the present study, to minimize in-flight time, nuclear electric propulsion system (NEP system) is suggested for human exploration to Mars. NEP system consists of CCMHD power generation system driven by nuclear fission reactor (NFR) providing electric power to the propulsion system and the variable specific impulse magneto-plasma rocket (VASIMR). In this study, modeling of power plant for NEP system and system analysis of it is carried out. Then Parameter are changed, the outlet temperature of NFR, the radiator temperature and the enthalpy extraction of MHD generator, in order to know how to minimize specific mass In the outlet temperature of NFR change, specific mass of NEP system decreases with an increase of outlet temperature of NFR. In the radiator temperature change, specific mass of NEP system have minimum point in radiator temperature. In the enthalpy extraction of MHD generator, specific mass of NEP system have minimum point in enthalpy extraction. Specific mass of NEP system less than ] / [ 2 kWe kg system uf03d uf061 could be expected.

Numerical study on acceleration performance in electrode configuration of linear MHD accelerator using CIP method

Many studies have been conducted on the different electrode configurations for the Faraday type channel in MHD accelerators, with special interest in the diagonally connected MHD channel. In the present work, the fundamental performance of an MHD accelerator is described a potassium seeded argon plasma. A comparative study of the acceleration performance will be conducted for the case of the Faraday segmented configuration, the diagonal configuration, and two different geometries for the Hall configuration. The physical model implemented is based on the two-temperature model, and the set of equations is numerically solved by means of the CIP method.

Numerical Study on Magnetic Nozzle for Efficient MHD Application

Studies on MHD accelerators and Magnetic Nozzles have been done for efficient propulsion applications. Magnetic Nozzles due to their magnetic field configuration have the advantages to confine the plasma in its interior, to give guidance to the particles through the field lines, and even the possibility to control the thrust and specific impulse by changing the magnetic field. In the present work we will study a hybrid system using Magnetic Nozzle at the inlet of an MHD channel in order to improve the performance of the last. The numerical approach will be based on a statistical modeling using kinetic theory. Some basic numerical results will be discussed.