Numerical Simulation of Transient Scramjet Combustion in a Shock Tunnel

Computational simulations of reactive flow within a hydrogen-fueled scramjet-like geometry experimentally tested in a free piston shock tunnel are presented. The experimental configuration (Odam and Paull, AIAA Paper 2003-5244) involves injection of hydrogen fuel into the scramjet inlet, followed by mixing, shock-induced ignition, and combustion. Experimental results showed significant heat release due to shock induced supersonic combustion. The present steady-state results, performed using a validated threedimensional Navier-Stokes solver, show generally good agreement with experimental data at fuel-off and fuel-on conditions but display a marked sensitivity to the wall temperature boundary condition. This indicates the possible need to account for transient wall heating in simulations of scramjet experiments conducted in short-duration shock-tunnel facilities. The computational results also provide some support for a “radical farming” hypothesis, advanced to explain the ability of the hydrogen-air mixture to auto-ignite at relatively low inlet contraction ratios