OPTIMIZED DESIGN OF A NEW GASOLINE DIRECT SWIRL INJECTOR

The internal flow characteristics of a gasoline direct injector (GDI) have been studied to improve fuel economy and reduce exhaust emissions. Computational fluid dynamics (CFD) is used to examine the internal flow of the GDI with the purpose of designing the optimum geometry of the injector. The design parameters include orifice length, cone angle, swirl angle, orifice diameter, and needle lift. Numerical results show that optimum sizes of the orifice length, cone angle, swirl angle, orifice diameter, and needle lift are 0.8 mm, 140°, 120°, 0.8 mm, and 70 m, respectively. The size of the lift does not affect the formation of the air core significantly near the tip of the needle compared with the ball-type needle. The vena contracta phenomenon near the orifice inlet can be released by smoothing the edge.