Cavitation Flow Characteristics in a Multi-Orifice Injector for Liquid Ammonia Fuel

Abstract Cavitation within the injector has a significant impact on the performance and stability of the liquid ammonia supply system. This study investigates the transient cavitation flow of liquid ammonia in a multiple-orifice injector using a combination of experimental and numerical simulation methods. First, a three-dimensional computational fluid dynamics (CFD) model of the injector was developed, which couples the volume of fluid (VOF) multiphase flow model, the realizable k–ε turbulence model, and the Zwart–Gerber–Belamri cavitation model. Then, the accuracy of the model was verified using experimental data from visualizations of liquid ammonia cavitation flow. On this basis, the effects of varying inlet pressure (40–80 MPa) and outlet pressure (1–3 MPa) on cavitation evolution were systematically studied to investigate the transient cavitating flow of liquid ammonia in the multi-orifice injector. The results indicate that the inlet pressure is the dominant factor determining cavitation flow characteristics. As the inlet pressure increases, the cavitation intensity, exit velocity, and mass flowrate all increase. Nozzles 1–3 are highly sensitive to changes in inlet pressure. Nozzles 4 and 5 achieve better flow output and stability owing to the expansion space in the pressure chamber. In contrast, the influence of outlet pressure is relatively small, with overall variations in all indicators not exceeding 3.2%. The buffering effect of the pressure chamber effectively mitigates the impact caused by outlet pressure fluctuations. This study clarifies the role of pressure conditions on the cavitation phenomenon in liquid ammonia injectors and provides direct guidance for designing high-performance and stable injection systems.