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Show 5.2.2 Distribution of flow and temperature Fig.9 shows flow and temperature distributions on horizontal cross sections. C a s es 1 (a), 2(a) a n d 3(a) all show cross sections at the height of burners in firing mode. C a s es 1(b), 2(b) a n d 3(b) all show cross sections at the identical height. C a s e s 1(b) a n d 2(b) show ones at the height of burners in flue mode whereas C a s e 3(b) shows that in the center of the height of a pair of burners. In C a s e s 1 (a), 2(a) and 3(a), the low temperature lazy flame is successfully predicted. The maximum temperature is about 1700K and high temperature region over 1500K spread over just a fourth part of the cross sections. The overheating of the muffle near the burners can be avoided by the FDI combustion. Moreover, a strong circulating flow of flue gas is observed in all cases. The muffle is expected to be heated uniformly by the strong circulation of hot flue gas induced by the FDI regenerative burners. C a s e s 1(b), 2(b) a n d 3(b) show a relatively high temperature field on the opposite side of burners in firing mode. Hot combusting flows injected from burners collide with each other at the height in the center of the two burners, creating a relatively hot region on the opposite side in the furnace. In C a s e 2(b), this high temperature region is coincidentally close to the burners in flue mode, resulting in relatively hot flue gas temperature as shown in Table 1. In C a s e 3(a), on the other hand, the burners in flue mode are located at the identical height of the burners in firing mode, presumably leading to a marginally lower flue gas temperature than in C a s e 2. C a s e 1 seems to create the recirculation most effectively, leading to the lowest flue gas temperature. The residence time of flue gas for C a s e 1 should be the longest among the three cases studied. 5.2.3 Heat flux distribution onto muffle surface Fig.10 shows the heat flux distribution onto the muffle surface. One-third of the muffle painted gray in Fig.8 is shown. Vertical and horizontal axes indicate the height and the radial direction of the muffle, respectively. The heat flux is expressed by a contour. To evaluate the heat flux generated by the switch-over operation of the regenerative burner system, two separate calculations were conducted for each of the firing modes by assuming a steady state. The two predicted heat flux distributions were averaged to derive the net heat flux to the muffle. While the uniform heat transfer to the muffle is expected by the FDI regenerative burner system as shown previously, the heat flux distributions show a substantial difference between the cases. In C a s e 1, where all the burners are installed in-line, flames are always generated at the same radial direction (0° in Fig.10), resulting in a relatively nonuniform distribution 7 |