Investigation of Flow Field Pattern in a GDI Engine at Different Speeds using Numerical Techniques 2013-01-2791

Numerical simulations were performed in a four stroke pent-roof SI engine under cold flow conditions at three different speeds (1000 rpm, 2000 rpm and 3000 rpm) to investigate the flow characteristics like swirl, tumble, turbulence, mass inducted and the formation of liquid film during cold start condition. The suction and compression strokes were simulated at the three speeds mentioned. Results show that swirl and tumble are increased from 1000 rpm to 2000 rpm whereas the increase is very low between the speeds 2000 rpm and 3000 rpm. The computational model was validated against the experimental data available in the literature. There is a slight increase in the mass of air inducted as the speed goes up. Further investigation with liquid film modelling reveal, presence of liquid film mass on the cylinder and intake region. Around 34% of fuel quantity converted to film mass in the port wall region of intake while using port fuel injection (PFI) at the entry of Siamese port. The piston region has around 8% of fuel as liquid film at compression TDC. Later this may lead to soot and Hydrocarbon emission. From these results CFD code can be confidently used to further investigation like port orientation, manifold, spray, film and mixture formation and combustion.