Influence of Valve-Wall Distance on the Intake Flow in High Performance I.C.E.

The fluid dynamic behavior of four-valve high performance engines were investigated at the steady flow rig. In particular, the intake phase was considered. A global characterization was performed using the discharge coefficient, while the Laser Doppler Anemometry (LDA) technique was adopted to define the flow field around the intake valves.

The purpose of the paper is to evaluate the influence of the valve-to-wall clearance on the flow distribution inside the combustion chamber.

The analysis showed that, at low valve-to-wall distances, velocities (and therefore the engine volumetric efficiency) increase as the valves move away from the cylinder. The dependence is very strong for small distance values (lower than 2.5 mm) while it becomes weaker as the valve-wall clearance increases.