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, Computat ional 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 des ign parameters include orifice length, cone angle, swirl angle, orifice dia meter, and needle lift. Numerical results show that optimum sizes of the or ifice length, cone angle, swirl angle, orifice diameter, and needle lift ar e 0.8 mm, 140 degrees, 120 degrees, 0.8 mm, and 70 mum, respectively. The s ize 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 co ntracta phenomenon near the orifice inlet can he released by smoothing the edge.