Numerical Simulation of Cavitation in the Conical-Spray Nozzle

The cavitation flow inside the conical-spray injector is numerically investigated using the mix-ture multiphase model and full cavitation model.Results indicate that the cavitation evolution significantly affects the liquid sheet thickness and velocity at the nozzle exit,which will further change the spray angle and droplet Sauter mean diameter.Based on the cavitation distribution inside the nozzle,the cavitation flow inside the conical-spray nozzle can be classified into four regimes,i.e.no cavitation,cavitation in-ception at inlet,developing cavitation at nozzle exit and super cavitation.The extension of cavitation to nozzle exit in the super cavitation regime significantly improves the fuel atomization by increasing injec-tion velocity and decreasing thickness of liquid sheet.A cavitation map for the conical-spray injector was developed by simultaneously varying the ambient pressure and injection pressure.It is found that the phe-nomenon of super cavitation only occurs in a narrow region where ambient pressure is very low.Therefore,the start of injection timing should maintain before the top dead center to ensure the occur-rence of super cavitation inside the nozzle in order to create better homogeneous fuel/air mixture for diesel PCCI engines.