Experimental Determination of Liquid Spray Drop Morphology Qualitative Information from Laser‐Diffraction Measurements

The Laser-Diffraction Technique (LDT) based on the analysis of the light diffraction pattern forwardly scattered by droplets going through a laser optical probe, reports a drop-diameter distribution. As reported by previous investigations this drop-diameter distribution is sensitive to the shape of the drops and LDT measures an equivalent-diameter whose definition has not been established so far. The experimental investigation presented in this paper tackles this very point. It has been motivated by the recent development of the surface-scale distribution to characterize liquid drops. Being measured from Image Analysis Technique (IAT), the scale distribution contains information on the shape of the drops of the spray. The experimental work consists in analyzing a series of sprays with LDT and IAT to measure the surface-based scale distribution. It is found that the virtual spray composed of spherical drops and whose diameter distribution is the one measured by the LDT has the same scale distribution as the actual spray. This result allows a relationship between the mean-diameter series and the mean-scale series to be established. This relationship is satisfied by the measurements and indicates that information on the droplet shape is available in the mean-diameter series reported by the LDT. The analysis of the LDT mean-diameter series confirms this point. The results reported by this experimental work participate to a better identification of the distribution measured by the LDT.