入口流场不均匀性对固体火箭发动机大膨胀比喷管内流场的影响

Influence of inlet flow inhomogeneity on flow field in the nozzle of solid rocket motor with large expansion ratio

在高机动飞行过程中,固体火箭发动机承受长时间的小过载会导致喷管入口处燃气方向改变,而药柱空间非均匀燃烧又会导致燃气密度分布不均匀,从而影响喷管入口处质量通量分布。二者均会造成入口燃气流动非均匀性,这是引起喷管流场不均匀性的主要原因之一,直接影响发动机性能。以膨胀比为100的固体火箭发动机喷管为研究对象,改变入口处质量通量分布规律与入射方向,结合计算流体力学软件研究入口流场不均匀性对喷管内流场的影响规律。结果表明:当喷管入口质量通量呈抛物面分布时,入口的不均匀性对喷管内流场影响较小,在喷管喉部位置不均匀效应基本消除;由俯仰过载导致燃气非垂直入射时,喷管入口位置流场周向不均匀性高达23%;随着燃气充分膨胀,不均匀效应减弱,在喷管扩张比达到92.8时,流场基本均匀,但是在有限扩张比条件下由入射角度导致的流场不均匀效应无法完全消除。

During the high maneuver flight,the solid rocket motor(SRM)is subjected to a long⁃time small overload,which will change gas direction at the nozzle inlet.The spatially non⁃uniform combustion of the grain can lead to non⁃uniform distribution of the combustion gases density,which will affect the mass flux distribution at the nozzle inlet.Both of them will cause inlet gas flow non⁃u⁃niformity,which is one of the main reasons for nozzle flow field non⁃uniformity and directly affects the SRM performance.In this pa⁃per,taking the SRM nozzle with expansion ratio 100 as the research object,the mass flux distribution and incident direction at the nozzle inlet were changed to investigate the effect of inhomogeneity at the nozzle inlet on flow field by using computational fluid dy⁃namics software.The results show that when the nozzle inlet mass flux is distributed as paraboloid,the inhomogeneity of the inlet has little effect on flow field in the nozzle,and the inhomogeneity effect is basically eliminated in the nozzle throat;when the gas is non⁃vertically incident due to pitch overload,the circumferential unevenness of the flow field at the nozzle inlet is as high as 23%.With the full expansion of gas,the non⁃uniform effect weakens,when the nozzle expansion ratio reaches 92.8,the flow field is basically u⁃niform,but under the condition of finite expansion ratio,the non⁃uniform effect caused by the incident angle cannot be completely e⁃liminated.