Influence of Injection Timing on In-Cylinder Flow and Combustion Performance in a Spark-Ignition Direct-Injection (SIDI) Engine

摘要

Particle image velocimetry (PIV) was applied to an optical spark-ignition direct-injection (SIDI) engine in order to analyse various turbulent properties of the flow-field. The engine was motored at 1200 RPM with an intake pressure of 100 kPa, while PIV images were acquired on the horizontal (swirl) plane. The flow was decomposed into mean and fluctuating components via spatial filtering with an 8-mm cut-off length. Five dual-injection timing strategies were analysed, ranging from two injections early in the intake stroke to two injections during the compression stroke. The in-cylinder pressure traces, indicated mean effective pressure (IMEP), and combustion phasing data suggested that engine performance is incredibly sensitive to relatively minor changes in injection timing. An expected global trend of increasing turbulence with retarded injection timing was clearly observed. Relationships between turbulent kinetic energy (TKE) and burn rate were present, but not as obvious as anticipated, as total kinetic energy (KE) and variations in large-scale flow structures were also found to play a significant role.