Abstract: The rocket plume and scramjet outflow interact with each other in the mixer of RBCC，inducingcomplex background flow field including shock wave-boundary layer interactions and shock wave-mixing layerinteractions. To study the characteristics of shock train forward movement in an engine mixer，an unsteady numer.ical simulation was conducted. The results indicated that with outlet pressure increasing in the mixer，the forward movement contained 4 motion periods，each containing two forward movement patterns，namely‘slow pattern’ and‘jump pattern’. Shock train structures had similar characteristics of spring. In the 2nd motion period，stream. wise length of shock leading part varied periodically from 16.5mm to 21mm. Further analysis indicated that thecharacteristics of‘jump pattern’were attributed to the wall adverse pressure gradient，and a positive relation laybetween the jump distance and gradient. Intensity variations of the leading separation shock and reflect shockbrought about the periodic changes of shock train structures，and then led to similar characteristics of springs in the forward movement process.

Key words: Rocket based combined cycle；Mixing layer；Shock train；Unsteady calculation

摘要： RBCC中火箭出口流动和冲压流道的空气在发动机混合室中相互作用，形成激波 -边界层、激波 -混合层等多种干扰耦合的复杂背景流场。为了深入研究发动机工作室混合室内激波串的运动规律，采用非定常数值计算的方法对激波串在混合室中的前传过程进行了研究。计算结果表明，随着反压的升高，激波串的前传过程包含 4个运动周期，每个运动周期中均包含缓慢前传和“突跃”前传两种运动模式；激波串结构呈现“弹簧”的特点，在第二运动周期中，激波串前缘的流向长度在 16.5mm～21mm周期性变化。进一步分析发现，背景波系在壁面产生的逆压梯度是“突跃”运动产生的主要原因，且“突跃”前传的距离和逆压梯度峰值成正相关；激波串前缘分离激波和反射激波强度的变化引起了激波串前缘激波形态的周期性变化，进而导致激波串在前传运动中呈现类似“弹簧”的伸缩特点。

关键词: 火箭基组合循环发动机；混合层；激波串；非定常计算