NUMERICAL-SIMULATION OF IGNITION IN SUPERSONIC REACTIVE SHEAR LAYERS

This study is a direct numerical simulation of a spatially evolving re active mixing layer of a hydrogen/air system. A second-order TVD schem e with full chemical mechanism was employed to observe the mixing and ignition process. Mixing efficiency and ignition location were investi gated under different convection Mach numbers. Techniques for enhancin g ignition are discussed, attention being given to the coupling of the shear layer growth rate and viscous dissipation. Results show that an increase of convective Mach number significantly decreases fuel-air m ixing efficiency, but enhances the viscous dissipation. As a result, a decrease of shear layer thickness enhances the auto-ignition at high Mach numbers. It was also found that an increase of hydrogen Velocity causes the shear layer to shift toward the air side, leading to a shor ter ignition delay time. Furthermore, the effect of instability of the shear layer on ignition was also investigated. It was found that an i mprovement of ignition was achieved by imposing a very small perturbat ion upstream.