Numerical Investigation of Thermally Choked Ram Accelerator in Sub-Detonative Regime

Abstract

Numerical investigations of thermally choked ram accelerator in sub-detonative regime have been carried out. The simulation solves axis-symmetric compressible Navier-Stokes equations and includes modern turbulent combustion models. The experimental operating characteristics of a four-finned projectile in a 38-mm-diameter tube loaded with premixed propellant gas of methane/oxygen/nitrogen at a fill pressure and temperature of 5.15 MPa and 300 K, respectively, are considered. Simulations for projectile Mach numbers of 2.98, 3.05, 3.21, 3.41, 3.6, 4.36, and 5.01 were carried out. The shear-stress transport turbulence model and the eddy dissipation turbulent combustion model are used to simulate the turbulent reactive flow around the projectile. Complex chemical reaction mechanisms have been modeled with one-step, two-step and five-step simplified global reaction models. Not surprisingly, the non-dimensional pressure distributions from the simulation using the fivestep reaction model are in better agreement with the experimental measurements than those from the one-step and two-step models. The simulations reveal some key features of the shock system around the projectile, which are important in determining the characteristics of the thermally choked propulsive mode. These findings are useful in understanding the characteristics of supersonic turbulent combustion processes in the ram accelerator.