Validation of a CFD Model for Coupled Simulation of Nozzle Flow, Primary Fuel Jet Break-Up and Spray Formation

A coupled simulation methodology for cavitating nozzle flow and spray formation has been developed at AVL and applied within the framework of the FIRE CFD code. In this approach a two-fluid model for cavitating nozzle flow inside the injector and a primary break-up model applied at the nozzle orifice are combined with the standard Discrete Droplet Model (DDM). Using an alternative calculation method presently also an approach with an Eulerian multi-fluid model applied for the nozzle and spray regions together is developed. A two-fluid model is used to simulate injector flows. The primary break-up model developed is based on locally resolved properties of the cavitating nozzle flow in the orifice cross section. The model delivers the initial droplet size and velocity distribution with droplet parcels released from the surface of a coherent liquid core. The characteristic feature of the results from the model is a remarkable asymmetry of the spray. Recent experimental findings from Chalmers University gained from a transparent model injector are used for model validation.