Investigation of liquid fuel jet injection into a simulated subsonic "dump" combustor

Basic experimental studies of the injection of liquid fuel into a two dimensional flowfield designed to represent a sudden-expansion "dump" combustor were performed under cold-flow conditions. Test conditions were as follows: 0.6 entrance Mach number, 25 PSIA total pressure, and nominally 75°F stagnation temperature. Two step heights were investigated, 1.0 in. and 0.5 in., corresponding to area ratios of 1.33 and 1.17. The investigation included Pitot and static pressure distributions, spark and streak shadowgraphs, surface flow visualization, direct photographs and videotape recordings. The backlighted streak and spark shadowgraphs were used to obtain jet penetration and break-up information. Oil drop surface flow studies showed details of the flow in the recirculation region behind the step. The injectant for these cold flow studies was selected as water, which was injected transversely to the air flow 1.0 in. and 0.5 in. upstream of the step at various flow rates. It was found that both the location of the injection port relative to the step and the step height had no measurable effect on jet penetration and break-up. Injectant accumulation on the combustor wall in the base-flow region was found to be substantial under some conditions, and the amount of accumulation was shown to be a strong function of initial liquid jet penetration height.