Experimental investigation to study convective mixing, spatial uniformity and cycle-to-cycle variation during the intake stroke in an IC engine

摘要

The work described in this paper focuses on experiments to quantify the initial fuel mixing and gross fuel distribution in the cylinder during the intake stroke and its relationship to the large-scale convective flow field. The experiments were carried out in a water analog engine simulation rig, and hence limited to the intake stroke. The same engine head configuration was used for the 3-D PTV flow field and the PLIF fuel concentration measuremdents. high-speed CCD cameras were sued to record the time evolution of the dye convection and mixing with a 1/4 deg of crank angle rsolution (and were also used for the 3-D PTV measurements). The captured sequences of images were digitally processed to correct for background light non-uniformity and othe rspurious effects. The results are finely resolved evolution fo the dye concentration maps in the center tumble plane. The 3-D PTV measurements show that the flow is characterized by a strong tumble, as well as pairs of cross-tumble, counter-rotating eddies. The results clearly show the advection of a fuel-rich zone along the wall opposite to the intake valves and later along the piston crown. It also shows that strongout-of-plane motions further contribute to the cross-stream mixing to result in a relatively uniform concentration at BDC, albeit slightly stratified by the lean fluid entering the cylinder later in the intake stroke.