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Show A 2000-gallon storage tank equipped with a low-rpm stirrer holds the CWS to be tested. A variable-speed, progressing-cavity pump supplies CWS to the atomizer and is capable of delivering 2 - 2 0 gallons/minute of slurry at a discharge pressure of 400 psig. The system is also equipped with an electric CWS heater that has a 100-kW capacity. With this heater, the CWS can be heated to temperatures in excess of 250°F. Droplet velocity, size distribution, and relative number density at any point in the spray can be obtained from laser diagnostics using particle sizing interferometry (known as the visibility technique). The method requires the same basic optical equipment as the dual-beam laser Doppler velocimeter (LDV) technique. The visibility and LDV techniques can provide non-intrusive local measurements of individual droplet size and velocity. The dual-beam LDV (shown schematically in Figure 3) consists of a laser, beam splitter, focusing lens, collection optics, photodetector, and signal processor. At the intersection of the two beams, which defines the measurement volume, a fringe pattern is formed by the interference of the two coherent beams. As a droplet moves across the measurement volume, it scatters light that is collected and processed by the signal processor. A typical signal is shown in Figure 3 and is known as a Doppler burst. The Doppler burst is made up of two components - an alternating current (ac) signal superimposed on a Gaussian "pedestal." The period of the ac signal and the fringe spacing can be used to determine the droplet's velocity. Droplet size can be determined from the "visibility" defined as : IMAX " "SUN IMAX + IMIN where IWA„ and IWX„T are defined as shown in the figure. Visibility MAX MIN turns out to be a simple function of (D/6) (where D = droplet diameter and 6 = fringe spacing) over a droplet diameter range of about 10:1. By |