MHD pulsed power generation and applications

Summary form given only, as follows. We have been proposing to use non-equilibrium MHD generator as a pulsed power supply for various applications. This system has inherent advantages of high power density, high reliability and high durability compared with combustion driven type equilibrium MHD generator. For this system, Non-equilibrium Plasma Generator (NPG), where light metal combustion with pure oxygen heat up working medium of inert gas, is used as a heat source. In this study, space applications are proposed. One possible space application is electro-magnetic launcher (EML). We examine possibility and basic characteristics of rail-gun type EML. There is the final reachable velocity for this system, which depends on supply current and aerodynamical drag force. For typical conditions, maximum velocity and rail length are around 2 km/s and 10 km, respectively, at applied current of 1 kA. Required electric power is about 1.1 GW. We successfully design an MHD generator for this application, whose inner and outer radii are 2.6 m and 4.6 m with the channel height of just 1 m. In order to increase acceleration efficiency, we try to design segmented rail, which can reduce energy stored by the rail inductance. Optimization is achieved and required power can be remarkably reduced compared with the single rail system. Secondary, fundamental performance of an MHD accelerator is studied, whose application will be an MHD assisted scramjet engine for hyper-velocity vehicles. We can confirm acceleration of gas flow by Lorentz force by supplying external current. However, we found that the gas flow is decelerated at the entrance region for higher applied electric field. Supplied current must cause gas heating due to Ohmic heating with a plasma resistance. This Ohmic heating enhances negative pressure gradient along the channel and results in deceleration of gas flow for certain conditions in spite that current is introduced so as to make Lorentz force to accelerate it.