PERFORMANCE OF HIGH-AREA-RATIO ANNULAR DUMP DIFFUSER USING SUCTION-STABILIZED-VORTEX FLOW CONTROL

摘要

A short annular dump diffuser having a geometry conducive to formation of suction stabilized toroidal vortices in the region of abrupt area change was tested. The overall diffuser area ratio was 4.0 and the length-to-inlet height ratio was 2.0. Performance data were obtained at near ambient temperature and pressure for inlet Mach numbers of 0. 18 and 0.30 with suc¬tion rates ranging from 0 to 18 percent of total inlet mass flowrate. Results show that the exit velocity profile could be readily biased toward either wall by adjustment of inner and outer wall suction rates. Symmetric exit velocity profiles were inherently unstable with a tendency to revert to a hub or tip bias. Diffuser effectiveness was increased from about 38 percent with¬out suction to over 85 percent at a total suction rate of 10 to 12 percent. At the same time dif¬fuser total pressure loss was reduced from 3.1 percent to 1.1 percent at an inlet Mach number of 0.3.