Research On The Combustion And Flow Process In The Scramjet Multi-Cavity Combustor

Numerical and experimental investigations were carried out in a multi-cavity scramjet combustor, and the inner flowfield and internal drag were compared of different cavity installation schemes.In the supersonic cold flow, the flow structures with and without fuel injection were compared with each other by different cavities installation schemes. Results revealed that, for cavities in tandem, the flowfield of downstream cavity was altered by the incoming flow, influenced by the upstream cavity and the fuel injection, enhancing the fuel exchange rate. For cavities in parallel, the interaction between cavities and the fuel injection promoted the development of the cavity free shear layer and the blending process of the fuel and the air.The flowfield of different cavity installation schemes were compared with liquid and gaseous fuel combustion in the multi-cavity combustor. Results revealed that the cavity just interact with the near wall incoming flow. The main fuel heat release zone was determined by the interaction process between the cavity and the fuel injection. For cavities in parallel, the combustion intensity and the flame holding ability were improved by the shocks induced at fore-corner and aft-corner of the cavity. For cavities in tandem, the upstream cavity prolonged the fuel residence time in the combustor, which could be easily ignited in the downstream cavity. The downstream cavity provide a continuous ignition source, increasing the fuel preheating and precombustion in the upstream cavity.The process of ignition, flame diffusing and quenching out were investigated by high speed camera and Schlieren system. Results revealed that determined by the downstream heat release, all the processes were companioned with the change of the autoignition zones. The flame could propagate toward upstream by the evolution of the boundary separation zones, or diffuse to the opposite side by fuel autoignition or flame ignition.The internal drag of different cavity installation schemes were investigated in a multi-cavity combustor with constant area by the direct-connected force measurement system at the none-reaction and reaction state. It was indicated that the drag of cavity was mainly determined by the area that the free shear layer stroked the cavity rear wall in the non-reaction flow. Determined by the distribution of the main heat release zones, the cavity would produce negative or positive force in the reaction flow. More cavities lead to higher internal drag, and the drag in cold flow was higher than that in reaction flow with higher fuel equivalence ratio.Based on the above results, a novel multi-cavity combustor design method was proposed, which provided some technical support for higher performance scramjet combustor design.