A CFD Study of the Effect of the Needle Movement on the Cavitation Pattern of Diesel Injectors

The onset and development of the inner cavitating flow in Diesel injectors is analyzed in relation with the needle movement, using Computational Fluid Dynamics studies realized with moving mesh. Two real six-hole injector geometries have been considered, one with cylindrical nozzles, the other with conical nozzles. A full analysis of the flow results is presented, including a dynamic picture of the developing pattern. Results show that depending on the needle lift, the cavitation pattern varies strongly throughout the nozzle, and affects the characteristics of the flow at the nozzle exit. A kind of hysteresis in the development of the flow has also been observed between needle opening and closing.