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Show A Malvern 2200 particle size analyzer was used to measure the droplet size distribution of the sprays. This analyzer utilizes diffractive scattering of laser light to determine particle size distribution. The transmitter section of the instrument houses a 5 mW He-Ne laser, which is optically filtered and expanded to ~9 mm light beam. The laser was directed through the open windows of the spray chamber, to the receiver located on the opposite side. The 9 mm cylinder of light, of length equal to the width of the spray chamber, defines the location of the measurement section. The receiver houses a Fourier transform lens, optical alignment adjustments and a light sensitive diode array. The diode array is positioned at the focal point of the lens; therefore, undiffracted light of the laser will be directed at a point in the center of the detector array. The laser light will be diffracted (Franhofer diffraction) by the droplets or particles and the scattering angle is inversely proportional to the particle diameter. This diffracted light is also collected in the lens, and is directed to a concentric ring diode detector. Large diffraction angles will be directed to the outermost rings of the detector element. The solid state detector array contains ~30 rings of detectors, and allows two orders of magnitude range of particle size measurement. The size range depends upon the choice of interchangeable lens. A 300 mm focal length lens was used for this study, and provided a 5.8 to 560 micron particle diameter measurement range. Four drop size distribution models are incorporated in the computer, and can be used to fit the measured data: the Rosin Rammler, Log Normal or Normal Distributions and Model Independent. All data output is in the form of the best fit to the chosen model; therefore, the proper model choice is important. During the early stages of the test program, the slurry drop size distribution was found to be best represented by the Model Independent histogram which consists of 15 separate drop size classes; the shape of the size distribution is not assumed, as in the other three models. 17 KVB72-P327 D1 |