Effects of vacuum chamber and reverse flow on supersonic exhaust diffuser starting

A method to reduce the backflow into the vacuum chamber is demonstrated using a backflow arrester. The experimental data for a pre-evacuated large vacuum chamber with a backflow arrester show that the diffuser can be started at a faster rate as compared to the case without a backflow arrester. With regard to the inclusion of a nozzle. From high-altitude simulation experiments with a second throat exhaust diffuser (STED) system, the diffuser starting pressures are found to be nearly the same for a small or large vacuum chamber. However, a pre-evacuated large vacuum chamber requires more time to attain the steady-state cell pressure value than a small vacuum chamber. A large vacuum chamber that is initially started against atmospheric pressure exhibits a still slower starting transient. The hot-flow cases considered in the present study exhibit higher starting pressure values when compared to those of the cold-flow cases. The results indicate that a nozzle with the maximum lip width takes more time for vacuum chamber evacuation, but the nozzle and diffuser flows start very quickly.