Performance Evaluation of Second-Throat Diffuser for High Altitude Test facility

Abstract

Aimed at the improvement of ability of the high altitude test (HAT) facility for rocket engine, a new designed secondary-throat diffuser with ejection of low total pressure and supersonic cold air is proposed. The main structural characteristic of the new-designed diffuser is that: a groove is added to the start of the secondary throat of diffuser, and the supersonic cold air with low total pressure is ejected into diffuser to form the gas film, which leads to a reduction of the wall temperature and thermal load of the new-designed diffuser, and an improvement of the ability of diffuser holding shock train. The effects of cold air on flow characteristics and performance of diffuser are numerically investigated in detail under different conditions including total pressure and Mach number. The results show that the wall temperature along the diffuser increases with an increase of Mach number, and decreases with an increase of total pressure; with an increase of Mach number, the starting position of pressure rise moves upstream to the inlet of diffuser; and with an increase of total pressure, the starting position of pressure rise moves downstream to the end of diffuser.