Orifice Flow Dynamics in a Rocket Injector as an Excitation Source of Injector-Driven Combustion Instabilities

To investigate a hypothesis of the orifice flow-induced instability in rocket engine thrust chambers, single liquid oxygen (LOX) injector with an optically accessible module was used for experiments, water as simulant LOX. The unsteady pressure downstream measured using high-speed piezoelectric sensors under cavitating and non-cavitating intra-injector flow conditions. flows were directly visualized via backlight imaging camera through module. Cavitation initiated at cavitation number 2.05, bubble cloud formation started below 1.91. spectrum arising from comprises multiple peaks over broad frequency range, which can cause low- high-frequency instabilities. dominant frequencies decrease increasing drop, while during increase. excites second longitudinal acoustic mode tube. excited by becomes stronger when peak range whistling phenomenon is close to first mode. In conclusion, excitation mechanisms orifice-induced well identified, despite limitations