Oxidizer feed-system coupled instabilities have been observed in several liquid and hybrid propellant rocket engines, although they are not likely to be catastrophic for the latter. However, severe pressure oscillation in hybrid rocket may result in a significant reduction in the performance of the propulsion system restricting the application of the technology. In this research, feed-system coupled instabilities were studied theoretically and experimentally for hybrid rocket engines. Two test campaigns were performed to investigate the effects of the precombustion chamber and oxidizer injector configurations on engine pressure oscillation. Then, an extended mathematical formulation (including the injector pressure drop, the precombustion chamber residence time, the gas residence time, and the combustion time lag) has been proposed. The investigation was based on a transfer function using the stability limit analysis and the root locus method. It has been found that the configuration of the precombustion chamber plays an important role in the nature of the feed-system coupled instabilities, and a correlation was proposed to predict the fundamental frequency based on the oxidizer precombustion chamber residence time. The work has shown that the precombustion chamber length and the oxidizer injection velocity are key parameters that affect the period of the pressure oscillations in hybrid engines subjected to feed-system coupled instabilities.

在几种液体和混合动力火箭发动机中都观察到了氧化剂与进料系统耦合的不稳定性，尽管它们对后者不会造成灾难性的影响。但是，混合动力火箭中严重的压力振荡可能会导致推进系统性能显着下降，从而限制了该技术的应用。在这项研究中，理论上和实验上研究了混合动力火箭发动机的进给系统耦合不稳定性。进行了两次测试，以研究预燃烧室和氧化剂喷射器配置对发动机压力振荡的影响。然后，提出了扩展的数学公式（包括喷射器压降，预燃室停留时间，气体停留时间和燃烧时间滞后）。该研究基于使用稳定性极限分析和根轨迹法的传递函数。已经发现，预燃烧室的构造在进料系统耦合不稳定性的性质中起重要作用，并且提出了相关性以基于氧化剂预燃烧室的停留时间来预测基频。这项工作表明，预燃烧室的长度和氧化剂的注入速度是影响混合动力发动机中压力波动周期的关键参数，该混合动力发动机受到进料系统耦合的不稳定性的影响。已经发现，预燃烧室的构造在进料系统耦合不稳定性的性质中起重要作用，并且提出了相关性以基于氧化剂预燃烧室的停留时间来预测基频。这项工作表明，预燃烧室的长度和氧化剂的注入速度是影响混合动力发动机中压力波动周期的关键参数，该混合动力发动机受到进料系统耦合的不稳定性的影响。已经发现，预燃烧室的构造在进料系统耦合不稳定性的性质中起重要作用，并且提出了相关性以基于氧化剂预燃烧室的停留时间来预测基频。这项工作表明，预燃烧室的长度和氧化剂的注入速度是影响混合动力发动机中压力波动周期的关键参数，该混合动力发动机受到进料系统耦合的不稳定性的影响。