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超临界直流锅炉实际运行中,炉膛蒸发管爆漏多发生在热偏差管或水动力偏差管。采用改进的炉膛传热计算法,以理想的均值管为纽带,将偏差管工作状态和炉膛燃烧参数关联在一起,建立了偏差管流动和传热模型。根据均值管和偏差管两端压力相等,通过迭代计算确定偏差管工质流量,采用该模型考察了炉膛燃烧强度和工质冷却流量的匹配性,对蒸发管吸热不均、阻力偏差、异物堵塞或节流孔设计欠合理等引起的超温问题进行了模拟,并选用合理的换热系数关联式,对超临界锅炉全负荷变压运行蒸发管的壁温场进行了计算。结果表明,对于某1 000 MW超超临界锅炉,锅炉最大连续工况负荷运行时,当偏差管热偏差系数达到1.45,炉膛下辐射区受热面出现超温;锅炉100%汽轮机热耗验收工况负荷运行时,当局部阻力偏差达到0.292 MPa,偏差管工质的冷却流量降低到平均流量的57%,超温随即出现。
In the actual operation of the supercritical once-through boiler, the blast of the evaporation tube of the furnace mostly occurs in the hot deviation tube or the hydrodynamic deviation tube. By using the improved method of heat transfer in furnace, an ideal mean pipe is taken as a link, and the working status of the deviation pipe is correlated with the combustion parameters of the furnace. The flow and heat transfer model of the deviation pipe are established. According to the equal pressure at both ends of the mean pipe and the deviation pipe, the working fluid flow of the deviation pipe was determined through iterative calculation. The matching between the combustion intensity of the furnace and the working fluid cooling flow was investigated by this model. Blockage or orifice design is not reasonable and so on caused by over-temperature simulation of the problem, and use a reasonable correlation coefficient of heat transfer coefficient of the supercritical boiler full load transformer operation of the evaporation wall temperature field were calculated. The results show that for a 1 000 MW ultra-supercritical boiler, when the maximum continuous operating load of the boiler is running, when the thermal deviation coefficient of the deviation pipe reaches 1.45, the heating surface of the radiant area under the furnace appears over-temperature; During the load operation, when the partial resistance deviation reaches 0.292 MPa, the cooling flow of the working fluid of the deviation tube is reduced to 57% of the average flow rate, and the over-temperature occurs immediately.