论文部分内容阅读
针对上面级发动机大膨胀比喷管高模试车时发生的外压失稳现象,进行了高模试车时的稳定工作和启动过程数值仿真和实验研究。结果表明:对于室压4.5MPa,环境压力87k Pa,喷管面积比70的上面级发动机,稳定工作时,喷管承受的是内压载荷,不会发生外压失稳;不预抽真空启动时,喷管内的流场建立过程所需的时间很短约0.4s,而试验舱的压力只能依靠发动机的引射而降低,从0.4s开始喷管承受较大的外压载荷,直至10s左右试验舱的压力低于喷管内壁压力,在较长时间内喷管一直承受外压载荷,很容易发生外压失稳;预抽真空启动时喷管在0.14s到0.42s时间段承受外压载荷,且只在0.14s到0.25s内承受的外压载荷较大,喷管承受外压载荷的时间很短,不会发生外压失稳;启动前抽真空是避免喷管发生外压失稳的一种有效手段。
In view of the instability of the external pressure instability occurred in the high-level expansion engine of the above engine compared with that of the nozzle high-modulus test vehicle, the numerical simulation and experimental research on the steady operation and start-up process of high-test vehicle were carried out. The results show that for the upper stage engine with 4.5MPa pressure, 87kPa ambient pressure and 70% nozzle area, the nozzle withstands the internal pressure load without instability of external pressure. , The time required to establish the flow field in the nozzle is as short as about 0.4 s, while the pressure in the test chamber can only be reduced by the injection of the engine. The nozzle undergoes a large external pressure load from 0.4 s until 10 s Left and right test chamber pressure is lower than the nozzle wall pressure, the nozzle has been subjected to external pressure load for a long time, it is prone to external pressure instability; pre-vacuum start nozzle in 0.14s to 0.42s time period to withstand And only in 0.14s to 0.25s to withstand the external pressure load is larger, the nozzle to withstand external pressure load time is very short, external pressure instability will not occur; vacuum before the start is to prevent nozzle external pressure An effective means of instability.