| OCR Text |
Show flux distribution at the glass surface, which is more similar to that predicted for air Case 1 (Compare Fig. 9b with Fig. 9a), and lowere(' Ll.aximum bridgewall temperatures from 272SoF (1769 K) to 2696~F (1753 K). The 02 case with load ratio AS/A6 = 3.71 was consequently defined as baseline 02 Case 3. Further results for the baseline 02 Case 3 are depicted in Figs. 10 through 12. Fig. 10 shows the relative mass flux distribution of the baseline 02 case determined for the horizontal and two vertical cross-sections through the axes of Burners AS and A6. Note, that the mass flux density vectors shown in this figure were plotted in a scale ten times smaller than in corresponding Fig. 5 for the air case. Derivation of the flow patterns displayed in Fig. 10 is based on enclosed jet theory and flow superposition as described earlier. In particular, a recirculation strength of 15 times the inlet jet mass was utilized for both 02 jets. Fig. 10 shows that the jets do not significantly influence each other, however, due to its much higher absolute mass flow, jet AS determines the flow direction in recirculation regions. These features were confirmed in 3-D fluid dynamics calculations carried out independently for the burner configuration of Case 3. Gas temperature distributions (F) predicted for the 02 baseline Case 3 in horizontal and vertical burner planes are depicted in Fig. 11. Due to the high recirculation rates, maximum flame temperatures of 34320 F (2162 K) are only slightly higher than those predicted for air combustion (3364oF = 2124 K) • These gas temperature maxima are found in Flame AS which is hotter t.:·lan Flame A6 due to its much higher load . .f .Ly. 12 shows the refractory temperatures pred i.r-... .:- -r ry for 02 Case 3 at all walls of the furnace end-section. Maximum refractory temperatures of the roof are with 27320 F (1773 K) ' ca. 48 R (27 K) higher than those predicted for air combustion (Fig. 6). There is a clear correlation between the location of the maximum refractory temperatures and the adjacent gas flow. Maximum refractory temperatures are encountered there, where the gas flow vectors, especially in the flame tail, are directed towards the walls. In 02 Case 3, these areas are the breastwall region opposite to the AS burner and the roof section adjacent to this breastwall area. This behavior is less noticeable for Burner A6 due to the shorter high temperature flame zone. A similar correlation can be found between near wall flow direction and maximum heat fluxes, although the heat flux peaks are influenced as well by bulk radiation effects. Fig. 8b shows, that, conpared to 02 Case 2 with burner load ratio A5/A6 = 1 (Fig.7b), maximum heat fluxes to the glass shifted nearer to the 13 |
