Measurements of velocity and size of diesel fuel droplet by semiconductor laser 2-focus velocimeter

Abstract

A laser 2-focus velocimeter with a semiconductor laser as the light source has been developed for the measurements of velocity and size of diesel fuel droplet. Laser beam was concentrated to a small measuring volume for the droplet measurement near the nozzle orifice exit. The effect of needle valve movement on the droplet was clearly seen at 2.5D downstream from the nozzle orifice exit. It is clarified that the droplet size under the transient lift conditon at the needle valve opening is smaller than that under the full lift conditon even if the injection velocity is lower. The velocity fluctuation perpendicular to the nozzle axis is found to be larger under the transient lift condition than under the full lift condition.