Combustion characteristics of a dual-mode ramjet engine with a supersonic aerodynamic ramp injector

Abstract

The combustion characteristics of a liquid-hydrocarbon-fueled dual-mode ramjet combustor with a new injector, including a cavity-type flame holder, were investigated under inflow conditions of M 1.8, total pressure of 590 kPa, and total temperature of 930 K. The newly proposed injector uses various injection methods, such as an aerodynamic ramp, pre-mixing chamber, barbotage gas, and supersonic nozzle. The aerodynamic ramp injection method consists of four injectors with inclination angles of 40° and 80° and toe-in angles of 30° and 60°. This was adopted to increase the penetration height of the fuel while minimizing the total pressure loss. A pre-mixing chamber with a barbotage gas injection device was employed to enhance atomization and fuel–air mixing. In addition, a contoured Mach 3 supersonic nozzle was used to obtain a higher momentum through acceleration. For performance comparison, a combustor with a pre-mixing chamber and barbotage gas was used in the same manner, but injected by a cylindrical nozzle with a 15-degree of transverse angle. The ignition was initiated by a torch ignitor installed on the cavity floor with hydrogen pilot fuel. Once combustion stabilized, only the main liquid fuel was supplied. The Mach number was calculated using quasi-one-dimensional analysis based on the measured wall pressures and inlet conditions. The results showed that the model combustor with two types of injectors operated in the ramjet mode, which was subsonic near the flame holder and supersonic at the exit of the combustor. At the combustor outlet, the total pressure according to the equivalence ratio of 0.25 to 0.56, the newly proposed injector case showed a higher pressure level, steep increase, and more uniform pressure distribution than the baseline injector from the measurement result of the pitot pressure rake at the combustor exit.