To solve the problem of high NO_x emission of 600-MWe boilers in power plants, we established a cold gas–solid modeling testbed scaled by 1:5 for two-channel overfire air (OFA). A phase-Doppler anemometer was used to measure the characteristics of the outlet flow field of the two-channel OFA under different OFA rates. We also verified the industrial feasibility of this testbed under loads of 300 and 600 MWe. The influence of the OFA rate on the divergence angle of the outlet jet was small: When the OFA rate was increased from 15% to 35%, the divergence angle only increased by 2.2°. The attenuation of the axial velocity of the outlet jet increases with increasing OFA rate. For OFA rates of 15% and 25%, the jet penetration depth was between 1.5d and 2.5d (where d is the cone diameter of the OFA model in the cold-flow experiments). When the OFA rate was 35%, the jet penetration depth was between 2.5d and 3.5d. The jet maintained about 17% O₂ concentration at 1.4 m (about 11d) in the furnace under different boiler loads, and the concentration of emitted NO_x increased with decreasing load. Based on these findings, we propose the use of two-stage OFA: The jet at the outlet of the first-stage OFA ports should have a larger jet-divergence angle, and the other stage should have a larger jet-penetration depth to realize full mixing with the flue gas and to ensure high burnout and low NO_x emission.

中文翻译：

---

双通道过燃空气的过燃空气率对 600 MWe 锅炉流动和燃烧特性的影响

为解决电厂600MWe锅炉NOx排放高的问题，我们建立了1:5比例的双通道过火空气（OFA）冷气固建模试验台_。采用相位多普勒风速计测量双通道OFA在不同OFA速率下的出口流场特性。我们还验证了该试验台在 300 和 600 MWe 负载下的工业可行性。OFA率对出口射流发散角的影响很小：当OFA率从15%增加到35%时，发散角只增加了2.2°。出口射流轴向速度的衰减随着 OFA 速率的增加而增加。对于 15% 和 25% 的 OFA 率，射流穿透深度介于 1.5 d和 2.5 d之间（其中d是冷流实验中 OFA 模型的锥体直径）。当OFA率为35%时，射流穿透深度在2.5 d ~3.5 d之间。在不同的锅炉负荷下，射流在炉膛1.4 m（约11 d ）处保持约17%的O _{2浓度，并且排放的NO x}浓度随着负荷的降低而增加。基于这些发现，我们建议使用两级OFA：第一级OFA端口出口处的射流应具有较大的射流发散角，而另一级应具有较大的射流穿透深度以实现与烟气充分混合，确保高燃耗和低 NOx_排放。