Integrated Cavitating Injector Flow and Spray Propagation Simulation in DI Gasoline Engine

A methodology to simulate the injection process in the internal combustion (IC) engines by means of Computational Fluid Dynamics (CFD) is presented. Entire sequence of the gasoline injection processes, starting with a transient injector-flow simulation and continuing with break-up and spray propagation using AVL FIRE, is shown. In the first part, a multidimensional model for the cavitating flow in a multi-hole gasoline injector is presented, based on the two-fluid model and capable to simulate N-phase systems. Considered fluid components are liquid fuel and fuel vapor. Momentum and mass exchange between the two phases are accounted for. In the second part of the work, the link between nozzle flow and spray formation is established performing simulations including the break-up model. This calculates the initial conditions for the spray droplets, e.g., size and velocity, based on the local turbulent kinetic energy (TKE), velocity and phase distribution at the nozzle orifice. Also the length of the coherent liquid core and the parcel release positions are provided by the model. The results demonstrate the capability to predict cavitating nozzle flow and its influence on mixture formation dynamics. The numerical results are compared with experimental measurements of spray propagation, droplet distribution, spray shape, penetration length, etc.