气液同轴离心式喷嘴是液体火箭发动机采用的极其重要的喷注单元类型。但其容易产生自激振荡，可能会诱发不稳定燃烧，严重影响发动机的研制，而目前对于自激振荡过程中喷嘴内部非定常流动过程的认识还十分有限。借助试验及数值仿真手段对液体中心式气液同轴离心式喷嘴自激振荡过程中液膜的运动形变轨迹、振荡的产生原因及压力扰动在喷嘴内部的传递过程进行了系统分析。研究发现：喷嘴内部流场的压力振荡是由于缩进室内部液膜的周期性堵塞作用产生的，且振荡最先发生于缩进室内部液膜外侧；此后，压力振荡会以一定的相位差通过气体环缝及内部离心式喷嘴向上游传递，从而引起环缝气体、中心气核压力发生相同频率的振荡；当自激振荡强度足够大时，便会引起集液腔压力振荡，且振荡频率与自激振荡频率一致。

The gas-liquid swirl coaxial injector is one of the most important injection elements for liquid rocket engines. However， this kind of injector is likely to suffer from self-pulsation， which may induce combustion instability and could even seriously affect the development of engines. At present， the understanding of the unsteady flow process inside the injector during self-pulsation is still very limited. By means of experimental and numerical simulation， this paper systematically analyzes the movement and deformation trajectory of liquid sheet， the causes of self-pulsation and the transmission process of pressure disturbance inside the liquid-centered swirl coaxial injector. It is found that the pressure oscillation of the flow field inside the injector is caused by the periodic blockage of the liquid sheet in the recess chamber， and the pressure oscillation first occurs outside the liquid sheet in the recess chamber. After that， the pressure oscillation is transmitted upstream through the gas annular gap and the internal pressure swirl injector with a certain phase difference， resulting in the pressure oscillation of the annular gap gas and central gas core with the same frequency. When self-pulsation intensity is large enough， it will cause the pressure oscillation of the liquid manifold， and the oscillation frequency is consistent with the self-pulsation frequency.