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

摘要： 为了探究来流参数对混合管道流场结构的影响，通过试验和数值计算方法研究了在不同马赫数、静压来流参数条件下的背景流场和激波串流场结构。试验采用高速纹影和压力测量设备分别进行流场的观察和测量，采用喷管支板结构将来流分为上侧二次流、一次流和下侧二次流。试验与数值结果均表明，背景流场中的背景波系、混合层均由支板后缘处产生，背景波系在壁面间反射并与混合层发生干扰作用，背景流场结构较为复杂。一、二次流的静压关系影响混合层的初始发展方向，导致θ从-9°~7°变化，而马赫数决定起始激波与混合层的夹角。依据前缘激波的反射类型、亚声速区面积等特征，混合管道的激波串流场可以分为规则反射型、临界反射型、正向马赫反射型和反向马赫反射型四种典型结构。临界反射型的波后流场在垂直流动方向上具有“亚-超-亚-超”间隔流动的特点。

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