Experimental study on mode transition of the dual-mode scramjet with two-staged-strut injectors

Abstract

In order to investigate the combustion mode transition in the dual-mode scramjet with two-staged-strut injectors, a series of dynamic fuel injection experiments were conducted at the inlet Mach number of 3.0, of which the corresponding stagnation temperature was 1899 K. A linearly adjustable venturi was designed to control the fuel mass flow rate continuously and a high-speed imaging camera was used to record the flame structures during combustion. Three combustion modes namely, pure subsonic combustion mode, dual-mode subsonic combustion mode, and supersonic combustion mode were found in the model combustor. By changing the fuel injection equivalence ratio of the upstream strut dynamically, the model combustor realized combustion mode transitions from the subsonic combustion mode to the supersonic combustion mode and in the opposite direction. A hysteresis was obtained in the combustion mode transition process. The model combustor translated from supersonic combustion mode to subsonic combustion mode at the equivalence ratio of 0.25, while it translated from subsonic combustion mode to supersonic combustion mode at the equivalence ratio of 0.27. The abrupt change of the flame stabilizations and the differences of the heat release under the different combustion modes brought about the hysteresis.