Detonation wave structure and thrust variation of a ram accelerator with different projectile velocities

A study was conducted to investigate the effect of velocity on the detonation wave structure and thrust of a ram accelerator using a simulation of a premixed, reacting flow over a conical projectile. The simulation involved solving the compressible reactive Navier-Stokes equations with a detailed chemical model in a channel with a supersonic stoichiometric hydrogen-oxygen inflow. Results showed that at projectile velocities lower than the Chapman-Jouguet detonation velocity, a thermally choked unstart occurs. As the projectile velocity increases, the overdriven detonation mode, trans-detonative mode, and super-detonative mode successively form. The maximum thrust was achieved at the lower velocity limit under the overdriven normal detonation condition, but decreased continuously as an oblique detonation wave formed. The super-detonative mode was distinguished by the smoothness of the tail thrust derived from the recirculation zone and ignition before the conical ramp led to an unstart at the upper velocity limit.