Mixing characteristics of coaxial injectors at high gas/liquid momentum ratios

A study of the spray of a swirl coaxial gas-liquid injector operating at hi gh gas/liquid momentum ratios is reported, Mixing and droplet size characte ristics of the swirl injector are also compared to a shear coaxial injector , currently being used in the space shuttle main engine fuel preburner, The injectors were tested at elevated chamber pressures using water as a liqui d oxygen simulant and nitrogen and helium as gaseous hydrogen simulants. Th e elevated chamber pressure allowed for matching of several of the preburne r injector conditions including gas/liquid momentum ratio, density ratio, a nd Mach number. Diagnostic techniques used to characterize the spray includ ed strobe backlight imaging, laser-sheet spray imaging, mechanical patterna tion, and phase Doppler interferometry. The results indicate that thr radia l spreading of the swirl coaxial spray is much less than was reported in pr evious studies of swirl injectors operating at atmospheric backpressure, Th e swirl coaxial spray did, however, exhibit a smaller overall droplet size.