Effect of continuous Mach number variation of incoming flow on ram–scram transition in a dual-mode combustor

Abstract

Experimental and numerical investigation for a strut dual-mode combustor has been conducted in this paper. A Laval nozzle of alterable throat area is developed to change the incoming flow Mach number in isolator entrance. The Mach number of isolator entrance could be altered from 2.5 Ma to 2.0 Ma. By changing incoming flow Mach number, we obtained different pressure distribution variation at constant equivalence ratio. At 0.53 equivalence ratio, the pressure distribution in isolator and combustor has a different variation trend comparing with equivalence ratio 0.4. With incoming flow Mach number decreasing, the length of the shock train is shortened and pressure peak elevates. During the Mach number variation, the combustion heat release zone has a shift to strut. There is a balance for the combustion velocity and airflow velocity. The higher static temperature is also benefit for promoting combustion speed. The combustion zone shift makes more pressure increment act on the expansion segment to produce extra thrust under low incoming flow Mach number. Meanwhile, a ram–scram transition has taken place when the incoming flow Mach number variation. Further a subsonic discontinuity gap appears at constant segment and the thermal throat is chocked. The mass flow rate reaches up limits and leads to a two-stage pressure variation. The location of pressure variation would affect the combustor thrust.