| OCR Text |
Show 6 Both of these functions vary from 0 to 1, with high values indicating low NOx and high efficiency. For NOx concentrations greater than 25 ppm, a linear contribution to f is provided that can be no greater than 25%. Once NOx is below 25 ppm, a steep, fourth order slope contributes to f The [NOxlmax term is the maximum measured NOx for all three nozzles (61 ppm). The efficiency function, g, is zero when the efficiency is below 99.8%. Once the combustion efficiency is higher than this cutoff, g is the difference between the measured efficiency and the efficiency cutoff (99.8%) normalized by the maximum difference in efficiencies. This function is parabolic to provide a steep slope, and large contribution to J, at higher efficiencies. The NOx and efficiency cutoffs are derived from South Coast Air Quality Management District Rule 1146. The functions of f and g are shown in Figure 5. 1.00 0.80 -....... 0.60 )( 0 : 0.40 020 0.00 0 1.00 0.80 0.60 -=- C> 0.40 020 0.00 99.7% 10 20 99.8% 30 NOx ppm 40 99.9% Combustion efficiency 50 60 100.0% Figure 5: f([NOxl) and g(ll) Contributions to J The performance index for the three nozzles is shown in Figure 6 as a function of swirl intensity and excess air. The outline of each plot defmes the nozzle's operating limits and the darker areas identify the better conditions of operation. From this plot, it is much easier to determine where the conditions of good performance occur. The co-swirl nozzle, for example, shows good performance, J ~ 0.6, in the low swirl region from 5-10%. The radial and counterswirl nozzles exhibit better performance, J> 0.6, in the low swirl and high excess air regions close |
