In-cylinder PIV measurements have been made during the latter half of the intake stroke on a plane between the inlet valves for a single cylinder optical engine operating at engine speeds of 750, 2000 and 3500 rpm. Mean vector fields for an area of 42 mm by 34 mm have been produced with vectors at approximately 1 mm resolution. The vector fields show the development of the flow field in 1.6°, 2.4° and 3.2° steps for the three respective engine speeds. Tumble ratios have been calculated from these vector fields which show that a change in the flow regime occurs between 2000 and 3500 rpm. This is caused by one of rotating vortices becoming detached from the descending piston at the highest engine speed. 德國LaVision PIV/PLIF粒子成像測速場儀 汽車發(fā)動機多參量測試系統(tǒng) HighSpeedStar PIV相機