带烟气循环的W型辐射管流动传热及NOx排放特性

摘要

In order to solve the large wall temperature difference and high NOx emission of W-shaped radiant tubes, this article in-troduces a kind of W-shaped radiant tube with flue gas circulation. A mathematical model of the radiant tube is established and the ra-diant tube is studied by the method of numerical calculation. On the basis of the model’s reliability, the velocity field, temperature field and NOx emission are compared between the radiant tube and a conventional W-shaped radiant tube. The average gas velocity of the new radiant tube is three times that of the conventional radiant tube, and 57. 6% flue gas is involved in recombustion in the new ra-diant tube. The maximum combustion temperature of the new radiant tube is 2260 K, which is 192 K lower than that of the conventional radiant tube. The wall temperature difference of the new radiant tube is 166 K,which is 76 K lower than that of the conventional radiant tube. The NOx emission of the new radiant tube is 9. 9 × 10 - 5 , but the NOx emission of the conventional radiant tube is 7. 98 × 10 - 4 , nearly seven times higher.%为解决 W 型辐射管温度均匀性差和 NOx 排放过高的问题,提出了一种新型带烟气循环的 W 型辐射管,建立了该辐射管的数学模型,并运用数值计算的方法进行了模拟研究.在验证模型可靠的基础上,对带烟气循环的 W 型辐射管和常规 W型辐射管的流场、温度场和 NOx 排放进行了比较.结果表明：带烟气循环的 W 型辐射管气体平均流速是常规 W 型辐射管气体流速的3倍,有57.6%的烟气参与再循环；带烟气循环的 W 型辐射管中气体燃烧最高温度为2260 K,比 W 型辐射管低192 K；带烟气循环的 W 型辐射管壁面温差为166 K,比常规 W 型辐射管的壁面温差小76 K；带烟气循环的 W 型辐射管的 NOx 排放量9.9×10-5,而 W 型辐射管的 NOx 排放达到7.98×10-4,高出将近7倍.