| OCR Text |
Show assumptions in the data reduction method, uncertainties are introduced in the measured drop size distribution. An absolute size measureme K is possible with the optical defraction methods, but calibration of the instrument against a spray of known drop/particle distribution at comparable droplet density and velocity is necessary. In the case of relative comparison between data obtained under the same or at least similar conditions, the need for elaborate calibration is eliminated, assuming the error occurs in both sets of data, since only trends and relative changes are analyzed to identify a specific atomization mechanism present in one data set and not in the other. Figure 3 illustrates the optical system [10] used to determine the particle size distribution at one axial location (z = 10 c m ) and several radial positions in the spray. Mnt«r Cool Vour Slurry Sproy, L_ J Fooutlng L«ns Sly.*! Proc€?c >,„ Elecir-cr. I CL PanloU FUld lCD D O Otapuur Mulil-EtMsni Photo Olode Deiecaar Figure 3: Malvern 2200/3300 Particle Sizer Schematic. The spray nozzle was mounted on a 3-D traverse mechanism which allowed the positioning of the nozzle relative to the fixed optical system. The receiving lens was focused at the center of the spray and the defraction pattern was recorded by the ring-diode system of the receiving system. The Malvern instrument measures a light defraction pattern and fits a theoretical calculated pattern which depends on the drop size distribution to the measurement. Optimizing an assumed two-parameter Rosin-Rammlcr [11.12] size distribution of the droplets the S M D is obtained for the given conditions as plotted in the figures. Several experiments have been repeated to test the reproducibility of the data and minor discrepancies were observed. A typical data sheet is shown in Figure 4. 5 |
