Influence of water injection on performance of scramjet engine

In order to investigate the influence of water injection on performance of scramjet engine, a thermodynamic model with the constant cross sectional area heating process was developed to analyze the effects of water content and energy on performance of scramjet engine. The influence of water injection on the maximum fuel equivalence ratio of scramjet engine was also studied. The maximum specific thrust was obtained by optimizing the compression ratio of the inlet, the fuel equivalence ratio and the water content. Results show that the specific thrust of scramjet engine can be augmented by water injection at the cost of the decrease of fuel impulse. The maximum fuel equivalence ratio of scramjet engine can be increased by water injection at high flight Mach numbers, while slightly decreased at low flight Mach numbers. So thrust augmentation by water injection is more suitable for scramjet engines operated at high flight Mach numbers, which is further confirmed by optimization results of the maximum specific thrust of scramjet engine. Optimization results of the maximum specific thrust also show that improving the isentropic efficiency of the inlet and the maximum combustion temperature is beneficial to the augmentation of the maximum specific thrust of scramjet engine.