Three Dimensional Modelling of Flow and Turbulence In a Four-valve Spark Ignition Engine - Comparison with LDV Measurements

A study based on both three dimensional modelling of the internal flow and velocity measurements using Laser Doppler Velocimetry in a four-valve spark ignition engine was carried out. Two different optical arrangements, allowing three velocity component measurements, were used.

The intake and the compression strokes were computed and comparisons between computations and experiments were performed for three intake configurations. In configuration for which two intake valves are opened, specific computational difficulties arise and no satisfactory agreement is achieved. However, when only one intake valve is opened, the computed and measured velocity profiles are found to agree relatively well.

In the basic configuration, the internal flow is characterized by a tumbling motion. The combination with swirl in the two other configurations leads to the generation of complex flow structures which can be described as inclined tumble. One of the main features of these flows is an amplification of turbulence when the piston approaches Top Dead Center, which results in favorable conditions for the initiation of combustion.