An experimental investigation of the influence of base bleed on the base drag of various propelling nozzle configurations

摘要

Various propelling nozzle configurations with all-internal expansion were tested in external flow over the range of Mach number 0.7 to 2.2, in order to determine the effect of base bleed (i.e. the injection of low energy secondary air) on base pressure. An 'overall efficiency' is defined, which enables the effectiveness of base bleed, as a means of reducing the base drag, to be assessed. The results indicate that with supersonic external flow base bleed generally tends to raise the level of base pressure, but no improvement in the overall efficiency is obtained. At subsonic external speeds, the secondary air has a negligible effect on base pressure.