Modeling of Internal and Near Nozzle Flow for a Gasoline Direct Injection Fuel Injector

Abstract

A numerical study of twophase flow inside the nozzle holes and the issuing spray jets for a multihole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eighthole counterbore injector, from the engine combustion network (ECN). Simulations have been carried out for a fixed needle lift. The effects of turbulence, compressibility, and noncondensable gases have been considered in this work. Standard k–خµ turbulence model has been used to model the turbulence. Homogeneous relaxation model (HRM) coupled with volume of fluid (VOF) approach has been utilized to capture the phasechange phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine nonflashing and evaporative, nonflashing and nonevaporative, and flashing conditions. Noticeable holetohole variations have been observed in terms of mass flow rates for all the holes under all the operating conditions considered in this study. Inside the nozzle holes mild cavitationlike and in the nearnozzle region flashboiling phenomena have been predicted when liquid fuel is subjected to superheated ambiance. Under favorable conditions, considerable flashing has been observed in the nearnozzle regions. An enormous volume is occupied by the gasoline vapor, formed by the flash boiling of superheated liquid fuel. Large outlet domain connecting the exits of the holes and the pressure outlet boundary appeared to be necessary leading to substantial computational cost. Volumeaveraging instead of massaveraging is observed to be more effective, especially for finer mesh resolutions.