Motored SI IC Engine In-Cylinder Flow Field Measurement Using Time Resolved Digital PIV for Characterisation of Cyclic Variation 2006-01-1044

Time resolved digital particle image velocimetry (TRDPIV) data is presented for the in-cylinder flow field of a motored four stroke multi-valve direct injection spark ignition (DISI) optical internal combustion (IC) engine. It is widely accepted that IC engine performance, in terms of both engine emissions and efficiency, is fundamentally affected by the in-cylinder air motion. Therefore improved knowledge of the fundamental fluid flow processes present during the intake and compression phase of the engine cycle is required. More specifically, increased understanding of the flow field cyclic variation will facilitate accurate control of the mixing and ignition development. This paper highlights the application of a new TRDPIV system to provide both spatial and temporal in-cylinder flow field development over multiple engine cycles for improved understanding of cyclic variation. Measurements of the fluid motion at engine speeds of 1500 rpm and capture rates of 5 kHz, equating to a separation of 1.8 crank angle degrees between fields, was achieved. Results show the development of an initial high velocity jet during the intake valve opening period. A complex interaction with the cylinder geometry and piston crown is recorded, with the presence of a bulk motion recirculation and small scale turbulence. Comparison of individual cycles highlights the variation in small scale structures generated leading up to the point of ignition.