Numerical investigation of in-nozzle cavitation and flow characteristics in diesel engines using a multi-fluid quasi-VOF model coupled with a cavitation model

A numerical method based on the OpenFOAM framework is developed to investigate the in-nozzle cavitation and flow characteristics in a marine low-speed diesel engine. The Multi-fluid-quasi-VOF model, which can better simulate the momentum transfer between different phases instead of the standard VOF approach, coupled with a cavitation model are utilized to capture the interface of the phases inside of the nozzle. Furthermore, Large Eddy Simulation (LES) model incorporates the improved Schnerr-Sauer cavitation model based on heterogeneous nucleation theory. The method has been extensively validated through rigorous comparison with multiple experimental results, ensuring its reliability and accuracy. The developed method exhibits higher computational accuracy compared to the traditional Volume of Fluid (VOF) model under equivalent computational conditions. The simulation results demonstrate four distinct flow regimes of cavitation within the nozzle, with cavitation playing a dominant role during the transition from incipient to developing cavitation, while the Reynolds number primarily influenced the transition from developing cavitation to super cavitation. Moreover, the distribution of cavitation and turbulent vortex intensity in the nozzle exhibits consistency. Under the same pressure differential, the smaller orifice nozzle exhibits a wider cavitation area at the outlet, with a more pronounced radial expansion trend and stronger turbulence disturbance.