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Show 4.4.4 T in Staging-Jet Region The characteristic mean temperature (T)c ~ 1600K in the staging-jet region is obtained by comparing in-flame measurements among all burner scales tested under fuel staging conditions. Consistent with the modeling of this as a free jet diffusion flame, the mean temperature is independent of staging ratio. Within this torroidal volume in the furnace, the r'ms temperature fluctuation level is taken as (7 == O.I(T)c, consistent with that in the furnace region. 5. RESULTS ASSUMING PERFECT SIMILARITY The relatively simple scaling model described in §4 predicts flue gas NOx emissions at any burner scale and under any operating conditions. However since this is a scaling model, it is not intended to give the absolute NOx emission level, but only the NOx emissions relative to a given baseline. This baseline NOx level can be obtained from a single baseline measurement, which might typically be conducted at much smaller scale. The model then allows the measured baseline emission level from such a small-scale test to be scaled-up to yield the performance at any other scale and at other operating condi tions. To assess the validity of the model for this purpose, in this section it is applied to predict the NOx emissions performance over the full range of SCALING 400 burners and furnaces, with the only input being the absolute EINOx level from the 300 kW burner at baseline conditions (i.e. full thermal load, no preheat, no staging, no FGR, 0.56 swirl number). All parameters in the scaling model are determined from geometry or from the baseline in-flame measurements. In this section, all parameters remain unchanged over the entire range of burner scales and operating conditions. This assumes that perfect geometric, aerodynamic, and thermal similarity was actually achieved among all the burners and furnaces tested. In reality, the in-flame data show that the constant-velocity principle on which these tests were designed led, in some cases, to significant departures from perfect similarity. These departures will be accounted for in §6. However even under the assumption in this section of perfect similarity, results from the model will be seen to correctly predict most major trends in the data, suggesting that the model as formulated accounts for the essential NOx-producing sources relevant to this broad class of burners and furnaces. 5.1 Scaling with Burner Size Figure 11 compares the predicted and measured NOx emissions performance at baseline full-load conditions for all five primary burner sizes. The top left panel shows the contribution from each of the NO production sources in (6) to the total NOx emissions. The solid lines give the scaling for each of these sources as predicted by the scaling model under the assumption of perfect similarity, with the solid symbols representing the predicted contribution at each of the five test scales. (The open symbols account for departures from perfect similarity, and will be discussed in §6.) Note that the near-burner and furnace regions both -15how "ap ipcreasing contribu_t!on to the total NOx with increasing 14 |
