Experimental Study of the Cavitation Flow Characteristics in Diesel Engine Nozzle Under Different Injection Temperatures

As the terminal of injection system, the cavitation inside the injector significantly influences the atomization of fuel spray. The impact of fuel temperature on the cavitation inside the nozzle and the fuel distribution near the nozzle is investigated by using a scale-up transparent nozzle of the actual diesel engine nozzle. The no-unit number called cavitation number is introduced to characterize the potential of cavitation in the injector. The results show that increasing fuel temperature increases the saturated vapor pressure, decreases the cavitation inception pressure, and strengthens the cavitation intensity with the same cavitation number. The asymmetry of the cavitation zone is observed in the nozzle. Much more vapor bubbles due to cavitation at the bottom of nozzle surface are observed than these at the upper nozzle surface. When the super cavitation occurs, the cavitation flow in the nozzle has no significant change with the increasing of cavitation number, while the velocity decreases. Under the condition of same fuel temperature, increasing cavitation number can result in the increase of volume flow rate, the relative area of cavitation, and the spray angle near the nozzle, but decreasing the flow coefficient. Under the condition of same cavitation number, increasing the fuel temperature can result in the increase of volume flow rate and flow coefficient, as well as increasing the relative area of cavitation, which leads to a better atomization of the spray.