Fuel droplet dynamics and cluster formation in an industrial oil burner by Planar Droplet Sizing

An important problem in spray combustion deals with the existence of dense regions of droplets, called clusters, creating rich regions. We have measured droplet characteristics with and without combustion by PDA and PIV. But PDA being a point wise technique does not give any information on the dynamics of clusters and PIV being planar velocity measurement does not help in providing information on the clusters ’ diameters. Hence droplet dynamics and fuel concentration profile are investigated by means of planar laser methods. Therefore, another technique is applied, namely Planer Droplet Sizing. The simultaneous measurement of Mie scattering and Laser Induced Fluorescence (LIF) allows us to get instantaneous measurements of Sauter Mean Diameter (SMD) in a spray if the volumetric dependence of the fluorescence is ensured by using small concentration of dye. When using two different CCD to get the two signals, detailed calibration of the CCD response is required before getting absolute diameters. One CCD is coupled to an intensifier, as fluorescence intensity is very low. Each CCD is 1008 x 1016, 8 bits. Pixels are binned 7 by 7 to obtain final SMD map, being a compromise between spatial accuracy and noise. Furthermore, if the two CCD cameras are coupled to a double-pulsed Nd:YAG laser, two different instantaneous velocities can be measured by applying Particle Image Velocimetry (PIV) algorithms on both set of images. This technique is applied to an industrial gun-type burner. The cameras are placed at 90degrees from the laser sheet and their field of view (which is 10cm by 10cm) of the tw