Effects of Intake Ports on the In-Cylinder Air Motion under Steady Flow Conditions

The effects of two types of intake ports on the in-cylinder bulk flow and turbulence structure were investigated in steady flow tests by using laser doppler anemometry. The results, obtained at constant mass flow-rate in a plane 15 mm or 0.19 bore diameters from the cylinder head, confirmed the expected differences in the tangential flow pattern, but revealed similarity in the axial velocity distribution characterized by a large recirculation zone (RZ) attached to the inlet valve. In both cases the turbulence was found higher, more inhomogeneous and more non-isotropic in the regions of positive axial flow than in the RZ. Localized highly turbulent conditions have been identified and characterized as a consequence of bi-modal probability distribution functions (pdf) of velocity and aperiodic oscillations from one velocity regime to another. The utility of the present steady flow results in designing internal combustion engines must be assessed under motored conditions, but their implications on turbulence generation and development should be considered.