Cryogenic fluid dynamics of pressure swirl injectors at supercritical conditions

A comprehensive numerical analysis has been conducted to explore the development of liquid-oxygen (LOX) flow in pressure swirl injectors operating at supercritical pressures. The model is based on full-conservation laws and accommodates real-fluid thermodynamics and transport phenomena over the entire range of fluid states of concern. Three different flow regimes with distinct characteristics, the developing, stationary, and accelerating regimes, are identified within the injector. Results are compared to predictions from classical hydrodynamics theories to acquire direct insight into the flow physics involved. In addition, various flow dynamics are investigated by means of the spectral and proper-orthogonal-decomposition techniques. The interactions between the hydrodynamic instabilities in the LOX film and acoustic oscillations in the gaseous core are clearly observed and studied. The influences of flow conditions (mass flowrate, swirl strength of the injected fluid, and ambient pressure) and injector geometry (injector length and tangential entry location) on the injector flow behavior are systematically characterized in terms of the LOX film thickness and spreading angle. The axial and azimuthal momentum exchange and loss mechanisms are also examined.