In-Cylinder Flow Measurement of a Engine by Top-View Visualiz.ation(2) -In-Cylinder Flow

A PN system capable of top-view observation was built to measure internal flow over the entire cylinder area of a CI engine. The velocity measured on a plane and at each time during the intake, compression, and expansion processes was analyzed in relation to the piston behavior. During the intake process, the main flow is formed in the axial direction, so no organized flow was observed on the plane. Afterward, at the end of the intake and the beginning of the compression, the flow inside the cylinder was rapidly organized due to the piston's stagnation, and an organized flow appeared on the upper planes of the cylinder. As compression progressed, the organized pattern of the flow extended to the lower planes of the cylinder and intensified at the top. A very strong swirl behavior was observed at the top of the cylinder during the early expansion, which w as reobserved in the upper plane as a result of the flow within the bowl generated during compression. Therefore, even though direct access to the flow within the bowl was impossible, useful information can be obtained to infer this flow through top-view observations.