气体再燃区冷态流场特性的数值模拟

Numerical Simulation on Cold Flow Field Characteristics in Gas Reburning Zone

以某气体再燃技术改造后的220t/h锅炉为物理模型,采用标准k-ε双方程湍流数学模型对炉内冷态流场进行模拟计算,并用冷态试验结果对数学模型进行验证.结果表明：实测值与模拟计算值误差为5%~10%,该模型能较好地模拟实际流场工况;增加再燃喷口后,旋流区沿炉高方向拉长,提高了炉内火焰充满度;再燃喷口八点布置方式比四角布置方式的假想切圆直径大66%,且在喷口背火侧形成回流区,明显提高了再燃气流对上升气流的覆盖度;再燃量为5%时,再燃气流无法与炉内上升气流混合,最佳再燃量为15%;再燃区高度距离为3 600mm较为合理,增大再燃区距离对流场分布影响不大.

The boiler which uses the gas reburning technology was taken as a physical model to simulate the cold flow field characteristics in the furnace.A standard k-ε two-equation turbulent model was introduced,and the mathematical model was verified by the cold state test results.The results show that the deviation between the cold test results and the simulation value is about 5%~10%.So,the model can well simulate the actual boiler flow field conditions.The cyclone zone will stretch along the direction of furnace height after increasing the reburning spout,which is conducive to lengthen the furnace flame fullness.The diameter of the imaginary inscribed circle of the eight layout reburning jet is 66% larger than that of the corners arrangement.Moreover,by the former layout,a recirculation zone is formed in the fire back side of the vents,and the reburning airflow improves the coverage of the updraft.When the reburning amount is 5%,the reburning airflow can’t be mixed with the furnace updraft fully.The best reburning amount is 15%,and the height of the reburning zone of about 3 600 mm is a reasonable design.Increasing the distance of the reburning zone has little effect on the flow distribution.