Effect of Cycle-to-Cycle Variations in Spray Characteridtics on Hydrocarbon Emission in DI Diesel Engines : Visualization of Sac Inner Flow, Needle Valve Motion and Cycle-to-Cycle Variations in Diesel Spray

Abstract

To study cycle-to-cycle variations in diesel spray direction, images of the spray shape, needle valve motion and sac inner flow of multi-hole-type nozzles were recorded using a high-speed drum camera and two CCD cameras. It was observed that needle valve offset and one-sided sac inner flow during fuel injection induced fluctuation in spray direction and deformation of spray shape.Experiments on the effect of cycle-to-cycle spray variations on emissions under no load conditions and lower engine speeds revealed that when these variations are suppressed, it results in reduced hydrocarbon emission and less white smoke.