Interaction mechanism between shock waves and supersonic film cooling with cracking reaction

In order to understand the interaction mechanism between shock waves and supersonic film cooling with cracking reaction, supersonic film cooling using gaseous hydrocarbon fuel as coolant in terms of cracking reaction of the coolant, with and without shock waves interaction, is investigated numerically. Theoretically, cracking reaction may be accelerated by the shock wave interaction, which may enhance the mixing of the coolant and absorb heat, which will lead to contradictory effects on supersonic film cooling. However, it turns out that, with shock waves interaction, cracking reaction only absorbs more heat but barely has any effect on the mixing either locally or further downstream due to the momentum change caused by the reaction is extremely small and the energy change plays the dominate role. It is worth mentioning that oblique shock wave causes energy accumulation in the shock wave interaction region, which deteriorates supersonic film cooling. However, with the cracking reaction considered, the negative effect brings by the oblique shock wave is weakened by the cracking reaction due to the increment of chemical heat absorption caused by the energy change. It is found that the absolute temperature in the shock wave interaction and the relative temperature increment caused by the shock wave interaction to be the decisive factors of the chemical heat absorption increment, especially for high absolute temperature or relative temperature increments, and the effect of the local reactant concentration plays the dominant role. Furthermore, the extent of weakened chemical reaction on the negative effect due to the oblique shock wave depends not only on the chemical heat absorption but also on the local absolute temperature.