The spray plume geometry and fuel atomization characteristics of the gasoline direct-injection (GDI) multi-hole injectors are of paramount importance with respect to the GDI engine homogenous-charge combustion and emission characteristics. A major component of the GDI combustion system development is the optimization of the spray-targeting and mixture preparation. Significant R&D efforts are directed towards optimization of the nozzle design and the manufacturing process in order to achieve optimum multi-plume spray characteristics.
The Volume-of-Fluid Large-Eddy Simulation (VOF-LES) of the injector internal flow and near-field primary atomization has been receiving attention as a tool to enable analysis of the influence of nozzle design on the key spray parameters and reduce reliance on hardware trial-and-tests for multi-objective spray optimizations. In combination with current state-of the-art computational fluid dynamic (CFD) methods for simulation of spray atomization and transport processes, they afford a notable capability to expedite the injector valve-group and spray targeting optimization in order to reduce the time and costly hardware iterations.
The present publication reports studies of a GDI multi-hole injector valve-group and the corresponding spray plumes, with the aid of the current state-of-the-art CFD methods. The LES method is applied to study the structure and primary breakup of a single plume from a GDI multi-hole injector. A complementary study comprising the injector internal flow with the conventional Reynolds-averaged CFD method, coupled to the simulation of the spray atomization and transport processes using the stochastic Discrete Droplet method, has been performed. The correlation of simulated spray geometry with experimental data is encouraging.