Modelling of fuel injector in-nozzle cavitation and early spray breakup using a multiphase volume of fluid method

Fuel injector in-nozzle flow and early spray breakup is modelled using a compressible, multiphase Volume of Fluid Large Eddy Simulation implemented in the OpenFOAM environment. The volume fraction transport equations for liquid, vapour and gas phases are reformulated to include phase change source terms. These terms are modelled using the cavitation formulation by Schnerr, which is extended to eliminate non-physical mass transfer rates. The numerical method is validated by comparing the simulated mass flow rates, pressure and liquid volume fraction distributions at different cavitation conditions against published experimental data. Favourable comparison between simulations and experiments is achieved with minor discrepancies attributable to uncertainties in fuel properties and assumptions made in numerical models. Applications of the code to simulation of in-nozzle phenomena and primary breakup of the injected spray from a sharp edged nozzle reveals that in-nozzle flow separation, wall shear and cavitation contribute significantly to the fragmentation of the jet.