OCR Text |
Show the gas velocity profiles (28). Figure [7] shows similar temperature profiles made at location 3 for four stoichiometric ratios: 0.85, 0.95, 1.05, 1.15. It is evident that a stoichiometry of 1.05 produces a temperature at the center of the gas stream ~ 100K higher than the other air-fuel mixtures. The preliminary analysis of this data indicates that spectra taken at stoichiometries other than this value are comprised of a greater mixture (presumably temporal) of temperatures than those taken at 1.05 stoichiometry. This is somewhat indicated by the greater scatter of the data around the lower curve of Figure [7]. This would suggest that greater combustion instabilities are seen at this location in the gas stream at non-optimum stoichiometric ratios. The model developed to describe thermal characteristics of the test stand (20) has been updated to include the effects of the refractory lining (29). This model was used to calculate the gas temperature as a function of longitudinal distance from the combustor for the test stand configuration used in this work. The results are shown in Table 1 (30). Although the temperature differences between the measurement positions are basically in agreement, there is major disagreement between the absolute values of the calculated and measured temperatures. The measured temperatures are approximately 350K above the calculated values. Furthermore, the calculated temperatures show a peak value at a lower stoichiometry than seen experimentally. These discrepancies are under investigation. V. Seed and Slag Effects Temperature profiles of the gas stream were taken at the four locations shown in Figure [1] at a combustor stoichiometry of 1.05 when coal flyash (Illinois #6) and an 8:1 mixture of potassium seed (K2SO4) and flyash were injected. The flyash injection rate of 0.045 kg/sec corresponds to a 50 percent ash carryover condition. The seed-slag mixture was injected at a rate of 0.1 kg/sec to yield a 1 percent potassium mass concentration and a 25 percent ash carryover. Although the analysis of this data is not complete, a few aspects of the effect of the seed and ash on the CAR spectra will be discussed briefly. 17 |