Validation of a cavitation and turbulence induced model for the primary breakup of diesel jets

In this paper, the performance of an energy based CFD model for the primary breakup of high-pressure Diesel jets is presented. This version of the model was modified and further developed for different turbulent and cavitating flow conditions experimentally found inside the injection hole. A detailed spatial and temporal resolution of the cavitating flow in the hole is used by the model to deliver three dimensional sprays, providing all the starting conditions for the calculation of the secondary breakup of the Diesel spray by means of a Lagrangian approach. The characteristic feature of the model is the variable size and velocity distribution of the primary droplets as a function of the available breakup energy. Other main advantage of the model is the direct calculation of the droplet size distribution and spray angle on the basis of the flow properties, so that empirical correlations or measurement data are not needed as input for the calculations. The two-fluid Eulerian simulation for the cavitating flow inside the nozzle is followed by an Eulerian / Lagrangian approach outside the nozzle, using the Ansys-CFX CFD code for both stages of the process. Measurements carried out in the test facilities of the Continental Automotive GmbH in Regensburg for high pressure Diesel jets were taken to compare with the simulations, offering satisfactory performance.