1000MW超超临界旋流燃烧锅炉稳燃特性数值模拟与优化

使用realizable k-双方程模型,对一台1 000 MW超超临界机组对冲旋流燃烧锅炉的燃烧过程进行数值模拟,研究燃烧器一、二次风口形状对燃烧器热态流场、温度场分布的影响,并考虑了NO的排放量,对燃烧器3个改进方案进行了比较。数值模拟结果表明,二次风扩口角度及轴向长度较大时,火焰形状短而宽,NO排放浓度较低,煤质较差时燃烧不稳定;二次风扩口角度减小及轴向长度缩短后,中心给粉与原始结构燃烧器燃烧稳定性均增强,同时,锅炉NO排放量有所增加。二次风扩口轴向长度减少1/2,可以有效增加燃烧稳定性,且NO排放量无明显增加,为最佳改进方案。并与改进后试验结果进行对比,获得比较一致的结果。为大容量旋流燃烧锅炉燃烧劣质煤的燃烧不稳定问题提供参考和依据,为HT-NR3燃烧器的设计和运行提供一定的理论基础。

Numerical Simulation and Optimization on Stable Combustion of a 1 000 MW Ultra Supercritical Unit Swirl Combustion Boiler

The combustion process of a 1 000 MW ultra supercritical boiler was numerically studied with realizable k-model.The influences of burner heat flow field and temperature field distribution on different primary air and secondary air outlet structure shape were studied,and emission of NO was considered.Three improving programs of the burner were compared.The results of numerical simulation show that,when the secondary air outlet expanding angle and the axial length are large,the flame shape is short and wide,emission concentrations of NO is low.Combustion is unstable when the quality of coal is bad.When the secondary air outlet expanding angle is small and the axial length is short,combustion stability of coal center and original structure burner are both increased.At the same time,NO emission of the boiler increases.The combustion stability could increase effectively when the axial length of secondary air expanding outlet is reduced to 1/2 with the NO emission not being improved obviously,which was the best improvement program.That was compared with the improved test results,consistent results were obtained.It provides a reference and basis for large-capacity swirl boiler instability combustion,and a theoretical basis for the design and operation of the HT-NR3 burner.