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

The work described in this paper focuses on experiments to quantify the ini tial fuel mixing and gross fuel distribution in the cylinder during the int ake stroke and its relationship to the large-scale convective flow field. T he experiments were carried out in a water analog engine simulation rig, an d, hence, limited to the intake stroke. The same engine head configuration was used for the three-dimensional PTV flow field and the PLIF fuel concent ration measurements. High-speed CCD cameras were used to record the time ev olution of the dye convection and miring with a 1/4 deg of crank angle reso lution (ann Mere also used for the three-dimensional PTV measurements). The captured sequences of images were digitally processed to correct for backg round light non-uniformity and other spurious effects. The results are fine ly resolved evolution of the dye concentration maps in the center tumble pl ane. The three-dimensional PTV measurements show that the flow is character ized hp 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 t he wall opposite to the intake valves and later along the piston crown. it also shows that strong out-of-plane motions further contribute to the cross -stream miring to result in a relatively uniform concentration at BDC, albe it slightly stratified by the lean fluid entering the cylinder later in the intake stroke. In addition to obtaining phase-averaged concentration maps at various crank angles throughout the intake stroke, the same data set is processed fbr a large number of cycle to extract spatial statistics of the cycle-to-cycle variability and spatial non-uniformity of the concentration maps. The combination of the three-dimensional PTV and PLIF measurements pr ovides a very detailed understanding of the advective miring properties of the intake-generated flow field.