为掌握液体火箭发动机泵后供应系统的频率特性，进一步认识发动机研制过程中的稳定性问题，开展了模拟真实泵后结构的液流激励系统频响试验研究。利用声学闭端装置和转盘式激励器分别真实模拟了泵的硬声场反射边界和燃气发生器燃烧形成的脉动信号源，扫频获得了该液流激励系统在受迫振荡下的频率响应特性。研究发现：在30~230 Hz的研究频率范围内，激励源处可产生分频幅值为0.3~1.07 MPa的人工脉动压力信号；线性与阶梯扫频在识别频率方面并无差别，但在100 Hz以上线性扫频识别幅值比阶梯扫频平台处的真实幅值小；声学闭端装置具有明显的频率选择性，在安装声学闭端装置的试验系统中，闭端效果较好的频率段在研究频率范围中的占比为82.5%，闭端装置使该频率段范围增加了67%，试验系统呈现出良好的闭端边界；随着稳态流量增加，脉动幅值增加，且主路更明显地表现出系统整体的多阶谐振频率特征，前三阶分别为36、65、101 Hz；在以大阻抗元件分割的具有强边界的局部子系统内，重点表现出该边界下频率特性；对于纯受迫激励系统，沿激励传播方向相位依次滞后，在谐振点附近相位差产生较大变化，脉动压力在节流圈以及带长支路的三通前后会形成较大相位差。

To master the frequency characteristics of the feed system after pump in a liquid rocket engine and further understand the stability problems in the development of rocket engines， a test study is carried out on the frequency response of the hydraulic excitation system of the simulated structure after pump. The hard acoustic reflection boundary of the pump and the pulsating signal source formed by combustion of the gas generator are simulated by using the acoustic closed-end device and the turntable exciter， respectively， and the frequency response characteristics of the hydraulic excitation system under forced oscillation are obtained by sweeping the frequency. The results show that in the frequency range of 30-230 Hz， the excitation source can generate artificial pressure pulsation signals with a frequency division amplitude of 0.3-1.07 MPa. There is no difference between linear and stepped frequency sweeps in identifying frequencies， but the identification amplitude of linear frequency sweeps above 100 Hz is smaller than the real amplitude at the stepped frequency sweep platform. The acoustic closed-end device has obvious frequency selectivity. In the test system where the acoustic closed-end device is installed， the frequency band with better closed-end effect accounts for 82.5% of the research frequency range and the closed-end device makes this frequency range increase by 67%， demonstrating a relatively ideal closed-end boundary of the test system. With the increase of steady-state flow， the pulsation amplitude increases， and the main circuit shows more obviously the multi-order resonance frequency characteristics of the whole system， where the first three frequencies are 36， 65 and 101 Hz. In the local subsystem with strong boundary divided by large impedance components， the frequency characteristics under this boundary are highlighted. For a purely forced excitation system， the phase lags along the excitation propagation direction in turn； the phase difference changes greatly near the resonance point， and the pulsating pressure forms a large phase difference before and after the throttle plate and the tee with a long branch.