Study on combustion mode transition of hydrogen fueled dual-mode scramjet engine based on thermodynamic cycle analysis

Hydrogen fueled scramjet is a candidate for use as the engine of the aerospace plane for its high specific impulse. To further improve the engine performance, analysis of combustion mode transition for a hydrogen fueled scramjet engine was investigated in this study. In order to identify the differences between Scram- and Ram-mode cycles in propulsive and economic performances for selection and optimization of operation modes, a thermodynamic cycle analysis was made with a dual-mode scramjet engine. It was found through comparative analysis that the specific impulse of the Ram-mode cycle was superior to that of the Scram-mode cycle in meeting the specific thrust requirement. From the viewpoint of performance optimization, the combustion mode transition in a dual-mode scramjet engine should occur in the range of Mach number 6-7. It was therefore concluded that a dual-mode scramjet engine should be operated as much at the Ram-mode cycle as possible when the flight Mach number is less than 6, and the combustion mode transition between Ram-mode cycle and Scram-mode cycle should take place in the range of flight Mach number 6-7.