Flow in fuel nozzles under cavitation and flash-boiling conditions

Abstract

Cavitation plays a crucial role in various fuel systems and spray applications. Due to the limitation in experimentally measuring the cavitation flow in fuel nozzles, numerical simulations can be used as an alternative in exploring the underlying physics. Most of the previous simulations of cavitation flow in nozzles were carried out under isothermal conditions, which become invalid when the thermal effect is strong. In this study, we use OpenFOAM and a modified cavitation model to investigate the influence of thermal effect on fuel nozzle flow characteristics under cavitation and flash boiling conditions. The comparison with experimental data shows that the modified cavitation model can predict well the cavitation flow in nozzles. Vaporization caused by cavitation at the nozzle throat and vaporization caused by the flash boiling near the outlet are simulated under different conditions. Phenomena such as mass flow reduction, outlet velocity blockage, and the transition from cavitation flow to flash boiling flow are well predicted. Further results show that with the increase in the inlet fuel temperature, the cavitation at the throat and flash boiling at the outlet occur gradually and then mix under high-temperature conditions. With the decrease in the ambient pressure, the flow in the nozzle gradually transits from single-phase flow to cavitation flow and then to flash-boiling flow. Increasing the injection pressure can inhibit the generation and the growth of superheated vapor near the nozzle outlet.