Effective Specific Impulse of Secondary Flow Injected into a Rocket Nozzle

摘要

The effective specific impulse of secondary flow injected into a supersonic portion of a large area ratio nozzle was evaluated. An oxygen/hydrogen thrust chamber with a 4000N thrust level and a chamber pressure of 3.5MPa was used. The secondary was injected through 30 discrete holes at a 13:1 local area ratio into a nozzle with a 140:1 overall area ratio. The mass flow ratio of secondary flow to primary flow was varied from 1 to 5%. Experimentally obtained effective secondary flow specific impulse Is was compared with calculated results. The experimental Is value was consistently higher than the calculated value by about 20%, presumably because of mixing and heat transfer effects which were not taken into account in the theoretical calculation. The secondary flow film cooling effect was substantial and persisted up to the nozzle exit.