| OCR Text |
Show CONCLUSIONS From a combustion standpoint, it would be desirable for the size distribution of the atomized slurry to be essentially the same as that of the coal in the mixture. Then, ignoring the effects of the water in the slurry, it would be anticipated that combustion efficiencies would be essentially the same as for pulverized coal. The data presented above shows that this level of atomization was attained only at high air-to-fuel ratios. At low A/F ratios, there are significant amounts of large drops in the spray although the particle size data appears to indicate the opposite. One possible explanation that reconciles this difference was presented in this paper. The visibility technique has two principle restrictions as applied to coal-water slurry. First, the maximum particle size that can be measured with the technique is insufficient to measure the distribution of the largest droplets in the spray. Without this information, the actual mass represented by the measured size distribution is indeterminate and only inferences can be made. Secondly, the measurement of large size particles with this technique results in a large measurement volume; therefore, a probe or mechanical obstruction is needed to restrict the number density of droplets. To obtain information on the size distribution of large droplets in the atomized spray, we have an imaging measurement technique that is compatible with the existing laser hardware used with the visibility technique. Although the results are not reported in this paper, the imaging method works well and is used to count those particles with diameters in excess of 260 microns. Results obtained with this method appear to support the explanation of data trends given in Figure 8. Thus using both the visibility and imaging techniques, the mass distribution in atomized sprays of coal-water slurry may be obtained over the entire range of particle sizes present. -13- |
