On jet-wake flame stabilization in scramjet : A LES/RANS study from chemical kinetic and fluid-dynamical perspectives

A three-dimensional hybrid LES (Large Eddy Simulation)/RANS (Reynolds-averaged Navier–Stokes) study dedicated to understanding the jet-wake flame stabilization under high inflow stagnation temperature in a hydrogen-fueled dual-mode scramjet was presented in this paper. The computational method features a finite-rate PaSR (Partially Stirred Reactor) turbulent combustion model with a detailed hydrogen reaction mechanism. The simulation results agreed well with the experimental results on overall characteristics of the jet-wake flame stabilization mode. Furthermore, quantitatively satisfactory predictions were attained for wall pressures. From the chemical kinetic perspective, the jet-wake flame stabilization can be divided into two regions. In the upstream region, both premixed- and non-premixed combustion are responsible for radical production, and the former produces more heat release. In the downstream region, turbulent non-premixed combustion dominates the flame stabilization. From the fluid dynamic perspective, the premixed flame is sustained by the counter-rotating vortex pair in the leeward side of the jet plume, which creates a local region with enhanced fuel/air mixing and reduced local flow velocity. Non-premixed combustion is found in the leeward side periphery of the fuel jet.