Magnetohydrodynamic accelerator with equilibrium plasma

Abstract

Magnetohydrodynamic (MHD) has been identified as one of the technologies that is capable of producing hypervelocity, high flight dynamic pressure and clean-air wind tunnel simulations for development of air-breathing propulsion systems. In this application, an MHD accelerator is used to accelerate the plasma flow at the exit of the combustor. The objective of this study is to investigate the performance of an MHD accelerator for space propulsion system using equilibrium air plasma as the working gas. The fundamental performance of MHD accelerator such as flow performance, electrical performance, and propulsion performance are described in this study. The performance of Faraday type has been evaluated at different levels of applied current density and magnetic field. For diagonal type, the performance has been evaluated at different levels of applied current, magnetic field, and constant diagonal angle. The MacCormack scheme is employed in order to solve the set of differential equations with MHD approximations. In order to represent the actual application of the MHD accelerator propulsion system, working gas of air-plasma composed of diatomic molecules of nitrogen and oxygen seeded with potassium is considered. The MHD Augmented Propulsion Experiment (MAPX) channel designed by the National Aeronautics and Space Administration (NASA) is used in this study. The best performance of diagonal MHD accelerator is obtained by setting the constant diagonal angle of 55o. The optimum current required for propulsion performance is 300 A for a magnetic field of 2 T and constant diagonal angle of 55o. In this condition, the value of the exit flow velocity, thrust and specific impulse are 3848 m/s, 363 N and 2736 s, respectively. The propulsion performance of the Faraday type is better than the diagonal type for an electrical power input of greater than 1100 kW. The optimum performance when increasing the applied current and magnetic field is dominated by j x B Lorentz force acceleration. On the other hand, increasing the applied current and magnetic field will increase the Joule heating and the u x B term’s contribution which are detrimental to the propulsion performance. Moreover, the friction forces resist the flow performance, especially near the exit of the channel.