Sensitive factors of ethylene combustion heat release under different combustion modes in scramjet engine

An experimental study is conducted to investigate the sensitive factors affecting ethylene combustion heat release in a scramjet combustion under supersonic flow conditions with of Mach number 2.52, total pressure 1.34 MPa and total temperature 1 650 K. The effects of key configuration parameters such as the isolator length, injection distance, cavity depth, and throat size on the ethylene combustion heat release are systematically analyzed and compared. The results show that the sensitivity of ethylene combustion heat release to configuration parameters is closely related to the combustion mode. When the combustion is in the completely scramjet mode, the combustion heat release is insensitive to changes in configuration parameters, while the opposite is true when the combustion is in the dual-mode scramjet operation (scramjet mode). Later, as the equivalence ratio increases, the combustion gradually transitions to the dual-mode ramjet operation (ramjet mode), and the sensitivity of the heat release to changes in configuration parameters gradually decreases. Overall, the order of the influence of different configuration parameters on combustion heat release from high to low is as follows: throat size > isolator length > injection distance > cavity depth.