Study of shock train/flame interaction and skin-friction reduction by hydrogen combustion in compressible boundary layer

Abstract

A numerical study is carried out to investigate the shock train/flame interaction and skin friction with boundary layer combustion in compressible boundary layer. The Transition k−kl−w model is employed as the turbulence model and the finite-rate model is selected as the combustion model. The results showed that the skin friction could be reduced by 50% through boundary layer combustion while the pure-mixing case can only bring about a 10% drag reduction. The ignition of hydrogen in the boundary layer leads to a rapid reduction in skin friction. When a shock wave intersects with the flame surface, in addition to the reflection, it is also refracted, which will cause the change of both skin friction and heat transfer to the wall. Studies on the effects of air/fuel temperature ratio reveal that both the skin friction and heat transfer increase with air/fuel temperature ratio. When the concentration of H2O increases in airflow, the skin friction is enhanced as the mixing and combustion between oxygen and hydrogen is suppressed with H2O addition. The results of changing the air/fuel pressure ratios show that at high airflow pressure, the distance between the flame and the wall is reduced, leading to increase of heat transfer to the wall.