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.