Internal and Near Nozzle Flow Simulations of Gasoline Multi-Hole Injector (ECN Spray G) with Transient Needle Motion

In this work, the effect of transient needle motion on gasoline multi-hole injector’s internal and near nozzle flow was studied. Spray G nozzle, an eight hole counter-bore injector from the Engine Combustion Network (ECN), was considered as the fluid domain. Simulations considered the effect of turbulence, cavitation, flash-boiling, compressibility and non-condensable gases under transient needle lift. To model the two phase flow inside and outside the nozzle, the Homogeneous Relaxation Model (HRM) coupled with the Volume of Fluid (VOF) approach was used. HRM model is used in this study because it uses an empirical timescale to reproduce a range of vaporizations mechanisms i.e. both cavitation and flash boiling mechanisms. To model turbulence, the RNG k – ϵ model was used. Simulations were performed with two different boundary conditions for the outlet domain to investigate non-flashing and evaporative (Spray-G) and flashing (Spray-G2) conditions. The simulation results were qualitatively validated against the experimental images and quantitatively against the experimental rate of injection (ROI) profile. The liquid plume angle showed good agreement with that of experimental measurement. The results show that the simulation is capable of capturing the ROI accurately with upstream pressure boundary condition and transient needle lift profile. Furthermore, the results show that the hole-to-hole variation in the total injected mass was not very significant. The simulation was also able to capture the cavitation phenomena inside the nozzles and flash boiling in the near nozzle region.