In-Cylinder Swirl Flows Characteristics with Variable Valve Lift

摘要

In this paper,the investigation into in-cylinder swirl flow characteristics with reduced Maximum Valve Lifts(MVL)is presented.The experimental work was conducted in the modified four-valve optical Spark-Ignition(SI)test engine with three different MVL of 6.8 mm,4.0 mm and 1.7 mm.Particle Image Velocimetry(PIV)was employed for measuring in-cylinder air motion and measurement results were analysed for examining flow field,swirl ratio variation and fluctuating kinetic energy distribution.Results of ensemble-averaged flow fields show that reduced MVL could produce strong swirl flow velocity,then resulted in very regular swirl motion in the late stage of the intake process and the strong swirl flow can maintain very well until the late compression stage.By comparing swirl ratio for different MVL,it can be found that reduced MLV can significantly increase swirl ratio at all almost measured crank angles and on different measured planes.The reduction of MVL can also increase both high-frequency and low-frequency swirl flow fluctuating kinetic energy remarkably.