In-Cylinder Velocity Measurement Using Two CCD Cameras and Cross-Correlation PIV

A cross-correlation particle image velocimetry (PIV) system consisting of two CCD cameras was developed to measure in-cylinder air motion in automotive engines. By using CCD cameras instead of conventional cameras, it is possible to obtain the velocity vector field more quickly after photographing the particle images. Cross-correlation was adopted to compensate for the smaller pixed number of the CCD cameras, since this technique reduires fewer pixels than auto-correlation to obtain one velocity vector. In-cylinder air motion in both horizontal and vertical planes was measured with the PIV system for a tumble intake system and a reverse tumble intake system. In both cases, tumbling motion was clearly observed in the vertical section. With the tumble intake system, twin swirling motions were observed in the horizontal section. Large cycle-to-cycle variations were observed in the velocity vector field in both cases.