Experimental investigation of the effect of pressure and density ratio on the formation of the group-hole nozzle gaseous spray

As for spray-guided direct injection gaseous fueled engines, a few time is available for mixture preparation, exact determination of the gaseous jet characteristics emanating from the injector is very important. The main purpose of the present work is investigation of the effects of pressure and density ratios on the multi hole gaseous jet tip axial and radial penetration lengths and its velocity. For this, ultra high speed Schlieren imaging of the transient jet with high spatial and temporal resolution was utilized. jet images were analyzed using digital image processing method and the jet characteristics were extracted using an in house software which worked based on edge detection approach. Results revealed that regarding to the velocity curves, formation of the multi-hole gaseous jet is comprised of three stages of: emergence of the individual plumes, merging and penetration of the main spray. It was also found that changing the chamber gas density wouldn’t alter the maximum and minimum times in velocity curves and decreasing the density ratio of the injection gas to chamber gas would decrease axial penetration and jet tip velocity and increase jet spreading angle.