Effects of liquid-oxygen post biasing on SSME injector wall compatibility

TLDR: In this article, the effects of LOX post bias on the behavior of the spray near a chamber wall were investigated with inert propellant simulants in a high-pressure chamber.

Abstract: An experimental investigation has been carried out to examine the effects of liquid-oxygen (LOX) post biasing of a shear coaxial injector on the behavior of the spray near a chamber wall. The experimental work was performed with inert propellant simulants in a high-pressure chamber. Injector flow rates and chamber pressure were designed to match the space-shuttle-main-engine (SSME) injector gas-to-liquid density and velocity ratio at the point of propellant injection. Measurements of liquid mass-flux, gas-phase velocity, and droplet size were made using mechanical patternation and phase Doppler interferometry techniques. The measurements revealed that the liquid mass-flux distribution shifts away from the wall with increasing LOX postbias away from the wall. The shift in the liquid flux distribution was much greater than that caused by the angling of the LOX post alone. Gas velocity near the wall simultaneously increased with increasing LOX post bias away from the wall. The increase in wall-side gas velocity was caused by the higher fraction of gas injected on the wall side of the injector as a result of the eccentricity at the injector exit. The net result was a decrease in mixture ratio near the wall. Estimates of heat transfer and engine performance relative to the unbiased case are presented.