Hiroyuki Sugita

Influences of electrical conductivity of wall on magnetohydrodynamic control of aerodynamic heating

Influences of the electrical conductivity of the wall of a space vehicle on the control of the aerodynamic heating in Earth-reentry flight by applying the magnetic field are numerically examined using an axisymmetric two-dimensional (r-z) thermochemical nonequilibrium magnetohydrodynamic computational fluid dynamics code. Numerical results show that when the wall of an axisymmetric blunt body is assumed to be an insulating wall, applying a dipole-type magnetic field with r and z components pushes the bow shock wave away from the blunt body and reduces the aerodynamic heating. On the other hand, when the wall is assumed to be a conducting wall, the aerodynamic heating cannot be reduced by applying the magnetic field. This is because the strong Hall electric field on the r-z plane cannot be obtained in the case of the conducting wall, so that the large electric current density in the azimuthal direction cannot be obtained and the shock wave cannot be pushed away from the blunt body.

Behavior of He-Cs closed-cycle disk MHD generator connected to electric power system through line-commutated inverter

The basic characteristics of He-Cs closed-cycle disk MHD generator connected to an electric power system through a line-commutated inverter are investigated in detail by carrying out time-dependent numerical simulations for the whole interconnecting system. The simulation model is assumed to consist of the closed-cycle disk MHD generator with 100 MW thermal input and 40 MW electrical output, the double-bridge line-commutated inverter, the a.c. filter, the phase modifier, the double-circuit transmission line and the infinite bus. It is made clear that the generator is stable, and its performance is excellent at the nominal operating condition. The active power can be controlled by using the firing angle as the manipulated variable. This active power control method is, however, considered to be not advisable because the ionization instability occurs when the firing angle is near 90°. The operation of the generation system should be stopped as quickly as possible in the case of a continuous inverter fault because this fault induces remarkable fluctuations of the gas dynamical quantity distributions in the generator. The continuous operation of the generation system is usually capable in the case of power line fault because the generator returns to its nominal operating condition after the fault is cleared. The operation should be stopped only in the unusual case of a continuous power line fault without clearance.

Analysis of performance characteristics of pulsed MHD generator with gas–liquid two-phase flow

A preliminary analysis of two-phase flow in the pulsed MHD generator Pamir-3U is carried out. The two-fluid model for dusty gas flow is applied to treat the two-phase working body which consists of combustion gas and liquid particles of Al2O3. One-dimensional time-dependent calculations show that the velocity lag and the thermal lag between the two phases are large when the particle diameter is 15 μm. The lags become small when the diameter is small because the decrease of the diameter increases the momentum transfer and the heat transfer between the two phases. When the large Lorentz force develops a shock wave, the interaction between the two phases relaxes the shock wave. The increase of the particle diameter decreases the channel current and the power output because the increased diameter decreases the energy conversion from the liquid phase.

Analysis of pulsed MHD generator considering collision-coalescence and fragmentation of liquid particles

A two-phase flow analysis with a particle model is carried out for a pulsed MHD channel of which working body consists of the combustion gas of a solid propellant and liquid particles of AlsOs. The gas phase and the liquid phase interact with each other by the transfer of momentum and heat. The behavior of liquid particles is described as the statistical summation of each particle’s behavior by using the particle model, where the collisioncoalescence and the fragmentation of particles are taken into consideration. The average diameter of particles grows from 4pm at the nozzle inlet to 20 pm at the nozzle throat owing to the collision-coalescence, increasing gradually to 25pm through the downstream part of the generator duct. The fragmentation of particles occurs near the nozzle throat. The velocity and temperature distributions show that the behavior of the liquid phase along the duct lags behind the gas phase in velocity and temperature and that the growth of particle diameter increases the velocity lag and the thermal lag.

PRELIMINARY ANALYSIS OF GAS-LIQUID TWO-PHASE FLOW IN PULSED MHD GENERATOR

A preliminary analysis of two-phase flow in the pulsed MHD generator Pamir-3U is carried out. The two-fluid model for dusty gas flow is applied to treat the two-phase working body which consists of combustion gas and liquid particles of A^Os. One-dimensional time-dependent calculations show that the velocity lag and the thermal lag between the two phases are large when the particle diameter is 15 (i. The interaction between the two phases relaxes the shock wave. The increase of particle diameter decreases the channel current and the the power output.