OCR Text |
Show D Flame length 1.0 0.9 0.8 I 0.7 0.6 0.5 -I- 0.4 0.3 4- 0.2 0.1 0.0 50 100 150 200 250 300 350 Position along burner axis (cm) 400 N O calculated mixture fraction D NO experiment Stoichio. mixture fraction Figure 5. NOx emissions variation as resulted from measurements and from the numerical simulation, for the burner B placed in the refractory-lined furnace, and the calculated mixture fraction. Figure 6 presents the velocity, turbulent velocity and temperature profiles on the burner axis, as resulted from measurements, and from the numerical simulation, for the medium momentum burner fired in the water-cooled furnace. The results in Fig. 6 show that, although the overall variation of the velocity, turbulence and temperature profiles are correctly predicted by the simulation, the peak flame temperature is over-predicted by around 300 K. It is also noted that the simulation under-predicts the temperature in the beginning of the flame. This result is in agreement with the results obtained for the refractory-lined furnace, indicating once again the need for improved oxygen-fuel combustion models. The N O emission predicted by the AL model for the water-cooled furnace, medium burner case is compared with measurements in Fig. 7. The results are similar to the refractory-lined furnace in Fig. 5. Thus the AL model slightly over-predicts the N O emission, when compared to the experimental 15 |