Quantification of volumetric in-cylinder flow of SI engine usign 3D laser doppler velocimetry

The flow inside of an internal combustion engine is highly complex and varies greatly among different engine types. For a long time IC engine researchers have tried to classify the major mean flow patterns and turbulence characteristics using different measurement techniques. During the last three decades tumble and swirl numbers have gained increasing popularity in mean flow quantification while turbulent kinetic energy has been used for the measurement of turbulence in the cylinder.

In this paper, simultaneous 3-D LDV measurements of the in-cylinder flows of the three different engines are summarized for the quantification of the flow characteristics. The ensemble averaged velocity, tumble and swirl motions, and turbulence kinetic energy during the intake and compression strokes were examined from the measured velocity data (approximately 2,000 points for each case) by the 3-D LDV system. In-cylinder flow patterns were studied using ensemble-averaged velocity vectors in each vertical or horizontal plane, and in entire volume. The result showed that the flow is affected not only by the intake system but by the aspect ratio of the cylinder. Tumble and swirl ratios, and turbulence kinetic energy were quantified as planar and volumetric quantities. The measurements and calculation results were animated for the visualization of the flow, and hence ease to analysis. The animation can also be used for the comparison and validation of the flow predicted by CFD codes.