On compression level of hypersonic airflow in high-mach scramjet

High-Mach scramjet is one of the most promising air-breathing propulsion devices to realize integration of air and space transportation. The current paper investigates a key step in design of high-Mach scramjet, namely, the compression level to be executed. The influence of compression level on hydrogen-fuel scramjet performance was analyzed using the modified thermodynamic cycle analysis method for high-Mach conditions. The theoretical results indicate that different from classical thermodynamic cycle analysis, the scramjet thrust reaches the maximum when Mach number at the entrance of combustor approaches 3. The flow loss and heat release in scramjet reach a balance near the maximum thrust state. Excessive compression can cause severe flow loss, while insufficient compression will lead to poor combustion. The numerical simulation further supports the theoretical analysis. When compression level of airflow is inadequate, the heat release rate of fuel will significantly drop. To extended the ideal operating range of high-Mach scramjet, it is suggested that the flow loss in inlet and isolator should be minimized, and the combustion efficiency of fuel in supersonic environment should be improved.