High-speed micro particle image velocimetry studies of boundary-layer flows in a direct-injection engine

Mass and energy exchange processes near the in-cylinder walls have become increasingly important for internal combustion engine research and development. Heat-transfer and fuel-deposition processes are not well enough understood to fully predict their magnitude and temporal and spatial variation. To a large extent, improvements in modeling are limited because of a lack of experimental guidance on the dynamics of boundary-layer flows in engines. High-speed particle image velocimetry and micro particle image velocimetry were used to study the boundary-layer flow field at the cylinder head of a motored internal combustion engine for three different engine speeds (400, 800 and 1100 r/min). Velocity measurements were taken throughout the compression stroke and the beginning of the expansion stroke, and comparisons to the frequently used law-of-the-wall were made.The low-resolution particle image velocimetry images showed that the average bulk flow maintained a tumble flow throughout the compression and expansi...