Abstract: To understand the characteristics of isolator working under back-pressure condition produced by combustor，fluctuant pressure caused by combustion oscillation was simulated by unsteady numerical methods. The characteristics of forced normal shock-train oscillation were studied under incoming Mach 2. Results show that the leading edge of shock-train kept periodic oscillation at the same frequency with fluctuant back pressure，but the oscillation amplitude was negative correlated with frequency. When the frequency of fluctuant back pressure reaches 600Hz，the oscillation amplitude of shock train reaches 2.97% of the duct length. Under fluctuant pressure condition，shock-train could resist higher back-pressure which increases when frequency of back-pressure fluctuation increases. In addition，the forced shock-train oscillation contains two styles: one is the movement of whole shock-train and another is the relative movement of successive shocks. Under fluctuant pressure with low frequency condition(50Hz，100Hz)，the movement of whole shock-train is main style of shock-train oscillation. However，under fluctuant pressure with high frequency condition (300Hz，600Hz)，the relative movement of successive shocks becomes main style of shock-train oscillation gradually. Furthermore，hysteresis of shock-train structure occurs during the process of shock-train oscillation，and that is the reason why hysteresis of total pressure recovery coefficient occurs.

Key words: Pressure fluctuation；Normal shock-train；Forced oscillation；Isolator

摘要： 为了解隔离段在真实燃烧室反压作用下的工作特性，通过数值方法模拟燃烧室振荡燃烧引起的脉动反压，在来流Mai=2条件下，探讨了脉动反压引起的激波串受迫振荡特性。结果表明，在反压脉动条件下，激波串前缘位置周期振荡，其振荡频率与反压脉动频率一致，振幅与反压脉动频率负相关，反压脉动频率600Hz时，振幅仅为管道长2.97%；就抗反压能力而言，在反压脉动条件下，隔离段能承受比定常状态更大的反压峰值，且脉动频率越大，可承受瞬态反压峰值越大。激波串的受迫振荡包含两种形式:激波串整体位置的前后运动和激波节之间的相对运动。在一定程度内，反压脉动频率较低时(50Hz，100Hz)，激波串整体位置的前后运动是主要的受迫振荡形式，激波节之间的相对运动很弱；随反压脉动频率升高(300Hz，600Hz)，激波节之间的相对运动加剧，逐渐成为激波串受迫振荡的主要形式。另外，在激波串振荡过程中，激波串往上下游运动经过同一位置时，激波串形态会出现迟滞，这是导致总压恢复系数迟滞的原因。

关键词: 反压脉动；正激波串；受迫振荡；隔离段