Cold flow simulation for an Internal Combustion Engine with swirl flaps

The paper aims at CFD analysis of engine cold flow when swirl flaps are used. The CFD analysis was performed using a RANS-RNG turbulence model to predict the evolution of engine cold flow at different engine speeds for two operating conditions with swirl flaps and without swirl flaps. The results show that swirl flaps can increase the average turbulent kinetic energy by up to 30% for a speed range of 1000 - 2000 rpm. However, over 3000rpm swirl flaps will worsen volumetric efficiency due to the change in the cross section of fluid flow to the cylinder.