Analysis of the In-Cylinder Flow Field / Spray Injection Interaction within a DISI IC Engine Using High-Speed PIV 2011-01-1288
This study presents measurements of transient flow field and spray structures inside an optically accessible DISI (direct-injection spark-ignition) internal combustion engine. The flow field has a direct effect upon mixture and combustion processes. Given the need to increase the efficiency and performance of modern IC engines and thus reduce emissions a detailed understanding of the flow field is necessary. The method of choice was high-speed two-component particle image velocimetry (PIV) imaging a large field of view (43 x 44 mm₂). To capture the temporal evolution of the main flow features the repetition rate was set to 6 kHz which resolves one image per 1° crank angle (CA) at 1000 rpm. The crank angle range recorded was the latter half of the compression stroke at various engine speeds as well as various charge motions (neutral, tumble and swirl). Moreover, consecutive cycles were recorded allowing a detailed investigation of cycle-to-cycle variations. This was done by comparing the kinetic energy distribution for individual and ensemble averaged cycles. Here, the tumble charge motion showed a much greater intensity in kinetic energy than the neutral or swirl charge motion. The interaction of the tumble charge motion and the spray injection were investigated in detail. Properties of the spray injection such as penetration depth and spatial drift caused by in-cylinder flows were analyzed. A correlation between the flow field structures and the subsequent spray momentum of different injector types was deduced.