Numerical Investigation on the Needle-shape of Hollow-Cone Pressure-Swirl Type Gasoline Direct Injector 2006-01-1002

This paper focuses on the possibility of enhancing the atomization process by testing several type of needle for the pressure-swirl gasoline direct injector. Under similar operating condition, three types of needle geometry with two different swirl intensities were investigated within fuel-air pressure differential from 3.0 to 10.0 MPa with 0.5 MPa step size. Using a commercial computational fluid dynamics (CFD) codes, the liquid sheet thickness at nozzle exit, and initial spray cone angle of the injection were calculated by means of 2D-axisymmetric swirl technique using multiphase Eulerian approach. A swirl-dominated RNG k-ε viscous model was applied. The calculated liquid sheet thicknesses were compared with an empirical correlation. The results of the CFD calculation were used to determine the theoretical Sauter Mean Diameter (SMD) droplet size using another correlation found from previous experimental work. Outcomes from the calculations suggest that needle geometrical shape combined with swirl intensity has considerable influences on the formation of thin liquid sheet at nozzle exit, the initial spray cone angle, and the mean droplet size of the liquid fuel spray.