Fuel Effects on Spatial Variation of AFR in an SI Engine

A novel arrangement of four fibres was used to probe the fuel concentration at 4 different positions along the longitudinal axis of a transparent engine cylinder at 5 different times during the induction and compression strokes. By using a reference calibration experiment we derived variations in the air/fuel ratio at times in the engine cycle when the inlet and exhaust valves are closed. We used this technique to examine the effects of inlet-port swirl and injection timing for a number of fuels including 2 refinery streams. We also traced the different spatial distributions of spectrally resolved aromatic and paraffinic components from the same fuel during engine operation.