For achieving the strengthened low-NO_x combustion plus high burnout in W-shaped flame furnaces, a cascade-arch low-NO_x and high-burnout configuration (CLHC) is realized by positioning two burner layers in a 600 MW_e furnace. The gas/particle flow, combustion, and NO_x emission characteristics in the furnace are numerically evaluated at four upper/lower furnace depth ratios of C_W = 0.458, 0.500, 0.529, and 0.558 (C_W signifying the furnace throat shrinkage level) so as to disclose the impact of the furnace throat shrinkage level on the overall furnace performance and meanwhile establish an available C_W setup. Increasing C_W initially updates but then deteriorates the low-NO_x combustion performance. At the narrowest C_W = 0.485 setup, the gained slightly asymmetric combustion shows relatively lower burnout loss but higher NO_x emissions, while the widest C_W = 0.558 setup forms severely asymmetric combustion with apparently raised carbon in fly ash but relatively lower NO_x emissions. At moderate setups of C_W = 0.500 and 0.529, a symmetrical combustion pattern develops, showing the low-NO_x and high-burnout performance characterized as NO_x emissions of 700–707 mg/m³ (6% O₂) and carbon content in fly ash of 5.4–5.5%. In comparison to C_W = 0.500, the larger downward flame penetration, higher flame fullness, and lower CO emission at C_W = 0.529 suggest that a reasonable upper/lower furnace depth ratio prefers C_W = 0.529. Compared with a currently advanced low-NO_x combustion technology, the CLHC lowers again NO_x emissions by about 200 mg/m³ (6% O₂) while maintaining high burnout, which confirms the CLHC's availability.

中文翻译：

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上下炉深比对两段W型火焰炉强化低NOx燃烧性能的影响

为了在 W 型火焰炉中实现强化的低 NO _x燃烧和高燃尽，通过在 600 MW _e炉中放置两个燃烧器层来实现级联拱形低 NO _x和高燃尽配置 (CLHC) 。炉内气体/颗粒流动、燃烧和 NO _x排放特性在四个上/下炉深比C _W  = 0.458、0.500、0.529 和 0.558（C _W表示炉喉收缩水平）下进行数值评估，因此以揭示炉喉收缩水平对整体炉性能的影响，同时建立可用的C _W设置。增加C _W最初更新但随后降低了低 NO _x燃烧性能。在最窄的C _W  = 0.485 设置下，获得的略微不对称燃烧表现出相对较低的燃尽损失但较高的 NO _x排放，而最宽的C _W  = 0.558 设置形成严重的不对称燃烧，飞灰中的碳明显升高但NO _x排放量相对较低. 在C _W  = 0.500 和 0.529 的中等设置下，形成对称的燃烧模式，显示出低 NO _x和高燃尽性能，其特征在于 NO _x排放量为 700–707 mg/m ³(6% O ₂ ) 和飞灰中的碳含量为 5.4-5.5%。与C _W  = 0.500相比，C _W  = 0.529 时更大的向下火焰穿透、更高的火焰丰满度和更低的 CO 排放表明合理的上/下炉深比优选C _W  = 0.529。与目前先进的低NO _x燃烧技术相比，CLHC在保持高燃耗的同时，再次降低了约200 mg/m ³ (6% O ₂ ) 的NO _x排放，这证实了CLHC 的可用性。