发动机起动/关机过程中喷管侧向载荷试验

为了获得大面积比喷管在发动机起动/关机过程中的侧向载荷，搭建了喷管侧向载荷冷流试验系统，通过测量应变管感知的喷管侧向载荷和通过加速度传感器感知的喷管振动载荷，分析发动机起动/关机过程中喷管侧向载荷的变化规律。试验表明:试验喷管在发动机起动/关机过程中均存在3个峰值侧向载荷，起动过程中分别对应着初始正激波向稳定自由激波分离的转变过程、自由激波分离向受限激波分离的转变过程以及分离激波结构处于“末端振动状态”，关机过程则恰好相反，而且关机过程相对起动过程的峰值侧向载荷发生压比存在一定的迟滞效应；喷管壁面的周向应变对侧向载荷非常敏感，而壁面轴向应变却基本不受喷管侧向载荷的影响；喷管侧向载荷是激励喷管振动的主导因素，并在试验喷管发生“末端振动效应”时，振动加速度峰值达到最大为80g。 

Test of nozzle side load variation during engine start up and shut down

For the purpose of acquiring the side load of high area ratio nozzle during engine start up and shut down, the nozzle cold flow test system was established to investigate the nozzle side load variation during engine work processes, through measuring the nozzle side load using strain tube and nozzle vibration load using acceleration sensor. Test results showed that the test nozzle had three side load peaks during engine start up and shut down respectively, and the peaks corresponded to the initial normal shock transforming to steady free shock separation process, the free shock separation transforming to restricted shock separation process and the separation flow appearing “end effect” phenomenon; the occurring sequence of nozzle side load peaks during engine start up and shut down was on the contrary, and there was some hysteresis effect for the two processes; the nozzle circumferencial strain was very sensitive to the variational side load, but the nozzle axial strain was not affected by the nozzle side load at all; the variational side load was the primary factor of nozzle vibration, and the maximum acceleration peak was about 80g when the nozzle “end effect” occurred.