Experimental Studies of Liquid Injector Response and Wall Heat Flux in a Rotating Detonation Rocket Engine

The results of two experimental studies are presented in this document. The first was an investigation on the transient response of plain orifice liquid injectors to transverse detonation waves at elevated pressures of 414, 690, and 1,030 kPa (60, 100, and 150 psia). Detonations were produced using a predetonator which utilized hydrogen and

oxygen or ethylene and oxygen as reactants. For injectors of identical diameter, an increase in length correlated with a decrease in the maximum back-flow distance. A preliminary study using an injector of larger diameter suggested that for injectors of the same length under the same pressure drop, the larger injector was more resistant to back-flow. Refill time of the injectors was found to be inversely-proportional to detonation pressure ratio and injector stiffness, and a curve fit was produced to relate the three parameters.

The second experimental campaign was the hotfire testing of an RP-2-GOX rotating detonation engine. Total engine mass flow rates ranged from 0.8 to 3.5 kg/s (1.7 to 7.7 lbm/s) and static chamber pressures between 316 and 1,780 kPa (46 and 258 psia) were produced. In a majority of tests, between four and six co-rotating detonation waves were observed. Using an array of 36 embedded thermocouple probes, chamber outer wall heat fluxes between 2.8 and 8.3 MW/m² were estimated using an inverse heat transfer method of calculation. Performance of the RP-2 injector was assessed by relating to the information obtained in the prior injector response study.