关键词: 火箭基组合循环发动机;混合管道;背景流场;激波串;喷管支板

Abstract: To give a better understanding of flow structures in a mixing duct, experiments and numerical simulations are utilized to investigate the background and shock train flow field under different inlet Ma and pressure conditions. High-speed Schlieren technique and pressure measurements are used for data acquisition. Nozzle clapboards are applied to separate the incoming flow into upper secondary flow, primary flow and lower secondary flow. The experimental and numerical results both indicate that background waves and mixing layers in the background flow field are produced at the rear of the clapboards. The background waves reflect at the duct wall and interact with the mixing layers, together constituting a complex background flow field. The static pressure relationships between primary and secondary inlet flow define the initial direction of the mixing layer, leading to θ ranging from -9° to 7°, while the Mach number relationships affect the initial shock angle in the relation to the mixing layer. In the light of the refraction type of the leading shocks and subsonic zone area, the shock train structures in the mixing duct can be classified into 4 typical reflections namely regular reflection (RR), critical reflection (CR), forward Mach reflection (FMR) and reverse Mach reflection (RMR). The flow field behind the CR shock train structure is ‘sub-super-sub-super’ in the vertical direction to the flow.

Key words: Rocket-based combined cycle;Mixing duct;Background flow;Shock train;Nozzle clapboard