Experimental Investigation of Abrupt Change in a Scramjet with Variable Mach-Number Flow

To study an abrupt phenomenon of a scramjet in the Mach-number variation process, a scramjet model was tested in the simulated acceleration and deceleration conditions between the flight Mach numbers of 5.0 and 6.0. The results showed that once the flame stabilization changes, the pressure and thrust will meet the abrupt change simultaneously, while three typical flame stabilization and two types of transformation processes were found. One is the switching between the jet-wake flame and the cavity shear-layer flame directly, accompanied by one abrupt change. The other is the switching of the first two flame stabilizations, combined with the cavity shear-layer/recirculation flame, accompanied by two abrupt changes. The reduction in the range of the equivalence ratio and the process of increasing the Mach number will promote the appearance of the second type with two abrupt changes, and the process of increasing equivalence ratio and decreasing Mach number makes the first type with only one abrupt change more likely to occur. In other words, the characteristics of the abrupt change during the flame stabilization transition process are determined by the combined effect of the changing paths of the incoming flow condition and the equivalence ratio. The actual process of Mach- number variation has an obvious historical effect on the flame stabilization transition.