To explore the particulates formation process of GDI engine, a three-dimensional model of dual injection gasoline engine combined with intake PFI (port fuel injection) and GDI was established. And simulation was carried out to describe the process of spray impingement, mixture formation, combustion, and soot formation in-side the cylinder. The results show that, the soot is primarily generated at thick zone of mixture, and increasing the PFI proportion will effectively reduce the film mass and soot emissions. Increasing the PFI proportion to 15% the film peak mass in cylinder decreases 14.3% compare to the film peak mass of 100% GDI strategy, and soot mass fraction decreases 31.1%. Increasing the PFI rate to 35% the peak quality of film in cylinder decreases 40%, soot mass fraction decreases 77%. With GDI spray timing delay, wall film peak mass decreased firstly and then in-creased, at the same time, soot mass fraction decreased firstly and then increased too. Therefore, adjusting the injection proportion and GDI timing of dual injection engine are effect ways to decrease spray impingement, optimize mixture distribution and improve soot emission.
Keywords equivalence ratio, injection proportion, injection timing, uniformity index