Fuel Droplet Size Measurements in the Combustion Chamber of a Motored SI Engine via Laser Mie Scattering

An experimental study was made of the time and space resolved measurements of the diameter of the fuel droplets inside the combustion chamber which were resultant from the timed injection of liquid fuel into the intake port of a motored automotive spark ignition engine. The determination of the individual droplet diameter during the intake and the compression strokes was based on the intensity of the light scattered from the droplet which was subjected to the monochromatic irradiation of He-Ne laser with uniform intensity profile. A theoretical analysis was also done to simulate the evaporation history of a fuel droplet subjected to the highly transient environments in the combustion chamber of the engine. The results showed that the droplets survived at the last stage of the compression stroke while their diameters decreased with crank angle elapsed due to evaporation. The effects of engine parameters on the droplet diameter were extensively discussed.