Plasma and Mhd Control of Oblique Shocks

The paper reviews recent studies of supersonic/hypersonic flow and shock wave control using plasma energy addition and magnetohydrodynamics (MHD), focusing on the work by the Princeton University group and their collaborators. Applications include sonic boom mitigation and optimization of scramjet inlets. Experimental and computational studies of interaction of oblique shocks with laser-generated blast wave and thermal wake demonstrate the possibility of shock mitigation in a repetitive-pulse mode. Analysis of interaction parameter for MHD control of cold hypersonic flows with external ionization shows that significant interaction can be achieved with energy-efficient ionization by electron beams. The maximum achievable interaction parameter sharply increases with increasing Mach number and altitude; however, interelectrode arcing may limit the performance. For MHD control of scramjet inlets, nonequilibrium electrical conductivity is created by electron beams injected into the gas along magnetic field lines. At Mach numbers higher than the design value, the shocks that would otherwise enter the inlet can be moved back to the cowl lip by a short MHD generator at the first compression ramp. To increase air capture at Mach numbers below the design value, a heated region is used to create a “virtual cowl” and to deflect flow streamlines into the inlet. The best location of the energy addition region is near the intersection of the nose shock of the vehicle with the continuation of the cowl line, and slightly below that line. Stretching and tilting the energy addition region improves performance. By spending only a few percent of the enthalpy flux into the inlet, the air capture and engine thrust can be increased by 15-20%, with no loss in specific impulse.