Experimental Cold Flow Characterization of a Swirl Coaxial Injector Element

A full-scale swirl coaxial injector element has been designed as part of an effort to examine liquid oxygen and liquid methane (LOX-LCH4) combustion instability phenomena under lunar ascent engine operating conditions. The scope of the LOX-LCH4 study encompassed cold flow, low pressure combustion, and high pressure combustion experimentation in an effort to establish a fast response analysis methodology for evaluating injector performance. As a baseline investigation, the spray characteristics of the injector’s central LOX post, exclusive of the exterior LCH4 annulus, were evaluated at constant ambient back pressure, across a range of steady mass flow rates. The effects of mass flow rate variance on the swirling sheet’s free cone spray angle and penetration length were assessed. Droplet velocity and diameter measurements were mapped within the spray’s primary and secondary atomization regions. The impact of throttling on the injector’s atomization quality was also surveyed.