OCR Text |
Show In i o £o 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 /A- 2500 2000 l^--r.1500 U calculated u' calculated ~ B - U experiment •H "~ u' experiment "T calculated ^ • "T experiment 1000 500 50 100 150 200 250 300 350 Position along burner axis [cm] 400 o o !> 3 *-» 2 o> a E 0) Figure 3. Velocity (U), turbulent velocity (u') and temperature profiles along the burner axis, for the refractory-lined furnace equipped with the burner B, as resulted from measurements and calculations. Figure 4 presents the temperature profiles in radial direction, for three different axial locations, namely at 22, 82 and 142 c m from the burner outlet. As in Fig. 3, the numerical simulation leads to higher peak values in the flame, and under-predicts the measured values in the vicinity of the burner. These trends seem to suggest a delayed flame initiation, indicating that the combustion model is not sufficiently accurate in simulating the oxygen-fuel flame, both in the initial and at the peak phases. The temperature variation has a very important impact on the N O emissions. The N O profiles resulted from measurements and from the AL model in Fig. 5 show that the numerical simulation is in good agreement with the measurements. Figure 5 also presents the mixture fraction variation along the axis, specifying the flame length as assumed by the model. 13 |