The Influence of Cavitation and Aeration in a Multi-Fuel Injector

The internal flow field of a low-pressure, common-rail-type, multi-fuel injector is analyzed by means of numerical simulation and particular attention is devoted to the cavitation and aeration phenomena when using different fuel mixtures.The fluid-dynamics open source OpenFOAM code is used; and the original cavitation model (based on a barotropic equation of state and homogeneous equilibrium assumption) is extended in order to account also for gases dissolved in the liquid medium. The effect of air dissolution into liquid is determined by introducing the Henry law for the equilibrium condition and the time dependence of solubility is calculated on a Bunsen Coefficient basis.A preliminary study of test cases available in literature is carried out to address the model predictive capabilities and grid dependency. The calculated pressure distribution and discharge coefficient for different nozzle shapes and operating conditions are compared with the referenced experimental measurements.Finally, the influence of different fuel blends on the injector internal flow field under cavitating conditions is investigated to determine cavitating regions and injected mass flow rates for ethanol and ethanol/gasoline mixtures.