Nonequilibrium magnetohydrodynamic control of scramjet inlets

The paper is devoted to theoretical analysis of magnetohydrodynamic (MHD) control of forebody flow compression and air mass capture in scramjet inlets for vehicles that would fly at Mach 6-10. Due to the low static temperature, nonequilibrium air ionization and electrical conductivity are created by electron beams injected into the gas along magnetic field lines. Two-dimensional inviscid steady-state flow equations are solved jointly with equations describing electron beam-induced ionization profiles, plasma kinetics, and MHD equations. Several scenarios are considered. At flight Mach numbers 8 and 10, with forebody and inlet geometry designed for Mach 6, the shocks that would enter the inlet can be moved back on the cowl lip by placing an MHD generator at the first compression ramp. In addition to controlling the shocks, the MHD device would generate electric power; however, Joule heating would result in losses of total pressure. Another scenario is an on-ramp MHD accelerator that should increase mass capture at Mach 6 or 8 for a vehicle designed for Mach 10. Calculations show that this scenario has only disadvantages, as the MHD device consumes high power, reduces total pressure, and actually decreases mass capture due to Joule heating and thermal expansion of the gas. A modest increase in mass capture can be in principle accomplished in an MHD generator mode, if the magnetic field has components both parallel and orthogonal to the flow. However, this scenario requires unrealistically large volumes of strong magnetic fields, and the mass capture increase is due mostly to a nonuniform gas heating. The paper proposes a new concept of a virtual inlet, where a localized off-body energy addition is used to increase mass capture, while not reducing (and even increasing) total pressure at the inlet.