A Numerical Investigation of Nozzle Geometry and Injection Condition Effects on Diesel Fuel Injector Flow Physics

A three-dimensional homogeneous equilibrium model (HEM) has been developed and implemented into an engine computational fluid dynamics (CFD) code KIVA-3V. The model was applied to simulate cavitating flow within injector nozzle passages. The effects of nozzle passage geometry and injection conditions on the development of cavitation zones and the nozzle discharge coefficient were investigated. Specifically, the effects of nozzle length (L/D ratio), nozzle inlet radius (R/D ratio) and K or KS factor (nozzle passage convergence) were simulated, and the effects of injection and chamber pressures, and time-varying injection pressure were also investigated. These effects are well captured by the nozzle flow model, and the predicted trends are consistent with those from experimental observations and theoretical analyses.

The flow distributions (density, velocity, etc.) at the nozzle exit obtained from the nozzle flow simulations were further coupled with an Eulerian-Lagrangian Spray and Atomization (ELSA) model to investigate the effects of nozzle flow physics on the downstream spray atomization process. Both non-vaporizing and vaporizing sprays were investigated in this study.