Numerical simulation of magnetohydrodynamic thrust augmentation for pulse detonation rocket engines

Pulse detonation engines (PDEs) are the focus of increasing attention due to their potentially superior performance over conventional engines, as either an alternate for an airbreathing engine or a rocket engine. Due to its unsteady chamber pressure, the Pulse Detonation Rocket Engine (PDRE) system will either be over- or under-expanded for the majority of the cycle, with energy applied toward suboptimal impulse generation, especially at very high speeds and high altitudes. Magnetohydrodynamic (MHD) augmentation offers the opportunity to extract energy and apply it to a separate stream in the engine where the net thrust will be increased. With MHD augmentation, such as in the Pulse Detonation Rocket-Induced MHD Ejector (PDRIME) concept, energy could be extracted from the high-speed fluid in the nozzle and reapplied elsewhere in the fluid as a body force. The present work explored the potential performance of such propulsion systems. In the PDRIME, at the appropriate point in the PDRE cycle, the MHD energy extracted from the PDRE's nozzle is reintroduced to a separate bypass tube by an MHD accelerator which acts to accelerate the bypass air and impart a net positive thrust to the system over the course of engine cycle. An alternative configuration, involving application of a "magnetic piston" in the PDRE chamber, with and without PDRIME bypass, is also explored. The present simulations mainly involve use of detailed transient numerical simulations (quasi-one-dimensional and two-dimensional) for the exploration of the PDRE, PDRIME, magnetic piston, and other geometries, and comparisons with a simpler blowdown model are also made. Results show that potential performance gains and operational benefits for specific flight Mach number and altitude conditions may be achieved and that conditions creating the performance improvements are similarly predicted between quasi-1 D and 2D numerical simulations.