OCR Text |
Show slight increase in flame temperature over I800K substantially accelerates the thermal NO formation, the FDI combustion appears to be very effective for low NOx combustion. Figs.8(a) and (b) show a predicted flow pattern in the forge furnace for the conventional oil burner system and the FDI-regenerative burner system respectively. Similar to the results in -Figs.6(a) and (b), the FDI-regenerative burner system creates a relatively strong circulation of combustion products between as well as under the two billets compared to the conventional system. Figs.9(a) and (b) show predicted temperature distribution. The effect of the strong circulation on uniform temperature distribution observed previously in the reheating furnace is again identified. The FDI regenerative system generates a relatively low flame temperature, suggesting its superior performance of low NOx combustion. Heat Flux Distribution and Heating Curves of Slabs Figs.l0(a) and (b) show predicted heat flux distribution onto the slab surfaces in the reheating furnace for the conventional burner system and the FDI-regenerative burner system respectively. The heat flux is the sum of radi~tive and convective heat transfer. For the FDIregenerative system, two separate calculations have been conducted to simulate the switch-over firing of the regenerative system. Two sets of predicted heat flux distribution have been averaged, yielding the net heat flux to the slabs. Figs.l0(a) and (b) show incident heat flux distribution when the slabs' surface temperature is 300K (cold charge). As predicted from the temperature distribution shown in Figs.7(a) and (b), the FDI-regenerative system demonstrates more uniform heat flux distribution than the conventional burners. The FDI regenerative burner system, in particular, creates higher heat flux onto the lower surface of the slabs than the conventional burner system, leading to more uniform heat flux distribution between the upper and lower surfaces. Following the heat flux distribution, heating curves of the slabs in the reheating furnace have been predicted. Calculation of one dimensional thermal conduction has been conducted to predict transient temperature increase across the slabs. Temperature inside the slabs as well as on the top and bottom surfaces has been predicted. Figs.l1(a) to (d) show predicted heating curves of selected slabs. The slab selected for Figs.ll(a) and (c) is located near the center of the furnace. The slab is named "CONY -X2-Y3" and "REGE-X2-Y3" for the conventional and the fDI regenerative systems respectively. (Note that X2-Y3 corresponds to the coordinates in Figs.lO(a) and (b).) This slab shows the least uniform temperature across the slab for both of the conventional and the fDI systems. The slab selected for Figs.ll(b) and (d), named "xxxx- 7 |