Experimental investigation of effects of air throttling on combustion characteristics in a kerosene-fueled scramjet at Ma7

Under the condition of flight Mach number 7 (inlet Mach number of isolator is 3.0), it is very difficult for kerosene-fueled scramjet to achieve auto-ignition and flame stabilization. In order to solve this problem, air throttling is adopted as an auxiliary ignition measure, and the air throttling flux ratio (the ratio of air throttling flux rate to inflow flux rate) is 38%. The test was carried out in the direct-connected experiment platform of pulse combustion wind tunnel. The flow structure and flame development were studied by schlieren, flame self-illumination and wall pressure measurement. With air throttling, the non-reacting flow was stable without oscillation, and upper wall pressure near the throttling position was about two times of that without air throttling. In the results of room temperature kerosene reacting flow, the kerosene equivalent ratio was 0.37. Kerosene could not achieve auto-ignition without air throttling, while kerosene auto-ignition and flame stabilization were achieved successfully when air throttling on. However, the combustion had a short period of oscillation when air throttling off, and the oscillation period is 3.0 ms.