Multicomponent liquid and vapor fuel measurements in the cylinder of a port-injected, spark ignition engine

Fuel distribution measurements in the cylinder of a port-injected, spark ignition (SI) engine are presented with a discussion of the effects of injection timing, swirl, and engine speed. Planar laser-induced exciplex fluorescence (PLIEF) was used to study the liquid-and vapor-phase fuel distributions. Optical access to the cylinder was provided by placing a fused silica cylinder between the head and block of a production engine and using a Bowditch-type piston extension. Separate measurements were made with fluorescent tracers indicative of the light and heavy components of gasoline. A blend of four pure fuels mixed in proportions to give a distillation curve similar to that of gasoline was used for all measurements to achieve consistency in the base fuel as well as similarity with the vaporization characteristics of gasoline. These measurements indicate that the vapor-phase fuel distribution is strongly affected by the presence of liquid fuel in the cylinder, the amount of which varies with injection timing. The liquid that enters the cylinder is composed mostly of the heavy components of the fuel. Variations in the amount of swirl indicate that the vapor-phase fuel distribution also is affected by the bulk velocity field. Engine speed, over the range from 200 to 1200 rpm, did not exert a significant influence on the fuel distribution.