For a dual-mode scramjet engine, different combustion modes present different flame-stability mechanisms and different flow characteristics. Besides, thrust varies remarkably when mode transition occurs. Therefore, it is extremely important to discriminate combustion mode accurately, so as to capture flame location, measure the distribution of heat release and further optimize combustor design (i.e., configuration and fuel supplying). Since there is no effective experimental method to estimate combustion mode, a new judgment method is proposed in this paper and validation experiments were implemented in a direct-connected scramjet test facility. Multi-diagnostics, including wall pressure, high frame-rate schlieren, CH* chemiluminescence imaging, and TDLAS (tunable diode laser absorption spectroscopy), were used in these experiments. Distributions of temperature, velocity, Mach number and heat release were obtained simultaneously. These data can be used to discriminate combustion mode and relate different flow/combustion characteristic swith different combustion modes.
2015, 47(3): 389-397.