翼柱型药柱固体火箭发动机不稳定燃烧研究

Study on combustion instability of solid rocket motor with finocyl grain

列举了3种高装填、大长径比、翼柱型药柱、复合推进剂固体火箭发动机不稳定燃烧的现象,对其不稳定燃烧现象进行了频谱分析,将3种不稳定燃烧定位为中频、纵向声不稳定。分析认为,不稳定燃烧取决于发动机的设计固有频率及发动机燃烧室内部声能的各种增益和衰减之间的消长关系。抑制不稳定燃烧的有效途径是改变声腔的固有频率和减少声能增益、增大声能损耗。通过采取修改药柱结构以改变燃烧室声腔的固有频率和增大喷管阻尼的措施,使发生的不稳定现象得到了很好的抑制,可为同类发动机研制提供借鉴。

Combustion instability or oscillation combustion which occurs in three high loading fraction solid rocket motors using high energy composite propellant with finocyl grain was discussed.Spectrum analysis result indicates that the combustion instability in all the three motors mentioned above occurs in longitudinal medium frequency.The reasons of the acoustic combustion instability were also discussed.Whether the pressure oscillation will continue to grow or not depends on the design of the grain and the final result of amplifying or dampening to each type of oscillations in the chamber.The basic ways to prevent this kind of combustion instability are modification of the grain geometry in the combustion chamber and also the nozzle structure to increase nozzle damping effect.Static test results of the redesigned rocket motors indicate that the proposed methods can significantly eliminate the combustion instability and improve the motor internal ballistic performance.