Performance evaluation of regenerative cooling/film cooling for hydrocarbon fueled scramjet engine

Thermal protection is considered to be a significant challenge for scramjet engine. In this paper, a combined cooling method which combines film cooling (F.C.) with regenerative cooling (R.C.) instead of single regenerative cooling for hydrocarbon fueled scramjet engine by using gaseous hydrocarbon fuel coming out of the cooling channel exit as film coolant has been proposed to increase the engine's flight Mach number without bringing extra fuel on board. One-dimensional (1-D) model of the combined cooling in terms of supersonic combustion in combustor and cracking reaction in regenerative cooling channels has been built and validated in order to evaluate its performance. The calculation results indicate that the engine wall temperature can be reduced significantly with R.C./F.C. and the flight Mach number of engine can be increased by nearly 8% under the stoichiometric fuel flow rate when material limit of the engine wall is set to be 1300 K. It is found that the effect of film inlet temperature on the cooling performance can be ignored because of the high total temperature of main flow, while the flow direction inside the cooing channel will have significant effects on the cooling performance of R.C./F.C.. The heat flux imposed on the engine wall is less uniform with “parallel flow” inside the cooling channel and the cooling performance is better and more sensitive to the change of film injection position under this condition. In addition, the cooling performance of R.C./F.C. present a very slight change when the number of the slots stays at a very low value and 2-3 film slots may be more practical and useful for the hydrocarbon fueled scramjet engine.