Experimental study on selecting controlled parameter for the optimal wall pressure of dual-mode combustor

The dual-mode combustor model of a kerosene-fueled dual-mode scramjet engine was investigated through a series of combustion experiments with different mode on the resistance heating direct-connected test system at Northwestern Polytechnical University. The experiment simulated the actual combustion process under the conditions of an inlet total pressure ranging from 600 to 900 kPa, an inlet total temperature of 810 K, and an inlet Mach number of 2.0. The results show that as the equivalence ratio of kerosene increases, the combustor goes through three modes sequentially: pure scramjet mode, dual-mode scramjet mode, and dual-mode ramjet mode. The peak pressure ratio of the combustor corresponding to the combustion mode transition boundary is 1.95 and 3.5, respectively, and the Mach number at the exit of the isolator is 2.26 and 1.0, respectively. The mode transition boundary remains unchanged regardless of the inlet total pressure. When the position of the peak pressure point is stably located near the upstream cavity, the combustor operates in dual-mode ramjet mode, while when the position of the peak pressure point is stably located near the downstream cavity, the combustor operates in dual-mode scramjet mode. As the position of the measurement point gets closer to the downstream, the relative coefficient of wall pressure change becomes higher in terms of wall pressure measurement. The greatest variation in the relative coefficient of wall pressure occurs at x = 370 mm, indicating the highest sensitivity. It is the most suitable parameter for controlling the fuel flow of the dual-mode scramjet.