Thermal protection and drag reduction performances of shock-combustion-hydrocarbon fueled supersonic film cooling interaction under flight Mach 9

Gaseous hydrocarbon fueled supersonic film cooling is considered as a promising method for realizing thermal protection and drag reduction simultaneously in scramjet combustors. In supersonic combustors, especially under higher flight Mach numbers (Ma∞>8), shock waves are inevitable. In this paper, shock-combustion-hydrocarbon fueled supersonic film cooling interaction under Ma∞ 9 is numerically investigated, and the difference compared to that under Ma∞ 6 are also analyzed. The results indicate that, under both Ma∞ 6 and Ma∞ 9 conditions, for supersonic film cooling using inert fluid as coolant, shock impingement is a negative influencing factor of the film. However, for hydrocarbon fueled supersonic film, the film combustion consisted of spatial nonlinear endothermic/exothermic reactions, introduces beneficial factors for shock-supersonic film interaction, making shock impingement an effective method for controlling the thermal protection or drag reduction performance under different flight Mach numbers. It is found that, under Ma∞ 9 condition, shock impingement introduces negative effects on the drag reduction performance, due to the significant increasement of wall skin friction induced by momentum transport enhancement with shock interaction. Furthermore, shock impingement positions located before self-ignition point with lower shock intensity (P2/P1 < 1.5), or located after self-ignition point, can effectively regulate endothermic reactions process near the wall and improve the thermal protection performance. Moreover, on the contrary, under Ma∞ 6 condition, due to the more severe combustion and insignificant wall skin friction increase, shock impingement exhibits the function of promoting film combustion and leading to the transformation from film thermal protection performance to its drag reduction performance.