Investigation Of Combustion And Flow Process In Dual-Cavity Scramjet Combustor

Experimental method and numerical simulation were carried out on dual-cavity scramjet combustor with constant area in this paper. Firstly, in cold flow, the mixing process of hydrogen with incoming flow and the drag of cavities were investigated; in reaction flow the structure of flame was also investigated. Secondly, the flow character of dual-cavity combustor was compared with single cavity combustor's. Thirdly, the mechanism that dual-cavity can improve combustion intensity and flame holding ability was analyzed.Numerical simulation was used to analyze transverse hydrogen jet into cold flow from the top wall. The results reveal that most of hydrogen spreads in main flow, only a little proportion is rolled into cavity. For cavities in tandem, the downstream cavity has little influence on hydrogen penetration height and has less hydrogen than the upstream one; it is also true when cavities placed in parallel, but the pressure of downstream is raised because of the bottom cavity.Numerical simulation was also used to analyze the drag of single/dual cavity. The results reveal that the drag of single cavity increases with its depth; for cavities in tandem, the drag has no relationship with cavities' distance.High-speed photography was employed to investigate the ignition process of liquid kerosene induced by hydrogen and the frame structure when hydrogen and kerosene combust steadily. The results reveal that when equivalence ratio is small the area shaped by shear layer and aft wall of cavity near nozzle is a steady combustion region in scramjet. For cavities in tandem, the downstream cavity supplies sustaining frame which can light up the combustible mixture; for cavities in parallel, shocks induced around cavity in bottom wall impinge on frame and improve the intensity of local combustion, the opposite combustion zones can promote the combustion process.