Study on cavitating flow in different types of diesel nozzle orific

Cavitation in diesel nozzle orifice is a key factor to the atomization of fuel liquid jet. Nowadays, SAC-type nozzle and VCO-type nozzle are widely used in internal combustion engines. Based on automatically generated unstructured grid, a multidimensional simulation is performed on both orifices using multiphase flow model of Eulerian multi-fluid approach and cavitation model. Injection pressure, back pressure of nozzle, inlet rounded radius of nozzle orifice and inclination angle of nozzle hole, are included in analyzing the cavitating flow in nozzle and mass flow of nozzle exit. The results show that increasing injection pressure can easily lead cavitation. At high injection pressure, the change in mass flow of SAC-type nozzle is less than that of VCO-type nozzle. The outlet pressure of nozzle restrains cavitation and decreasing outlet pressure is helpful to generating fuel bubbles, which is favorable to atomization. Large inlet rounded radius and inclination angle of nozzle orifice make smooth flow of nozzle, generate less vapor bubbles and increase exit mass flow. Study shows that cavitaiton in nozzle orifice can not be neglected in in-cylinder fuel atomization process, especially in primary break-up of liquid jet.