循环流化床锅炉膜式水冷壁的热应力分析

为研究循环流化床锅炉膜式水冷壁的热应力问题,通过数值模拟的方法对顶棚拐点处水冷壁的温度、变形量和热应力进行分析。研究表明:向火侧到背火侧水冷壁的温度梯度变化较大,水冷壁的变形量极不均匀,在水冷壁管与鳍片接触处出现应力的集中。水冷壁减薄后,最大热应力先减小再增大,在减薄厚度为1.5 mm后热应力迅速增大,鳍片磨损减薄后水冷壁热应力增加速度逐渐变大,当热应力超过材料的许用应力时极易发生爆管。水冷壁减薄量超过自身厚度的21.4%时考虑对水冷壁管进行更换。对水冷壁最大热应力与鳍片减薄量间的规律拟合成函数关系式,对判断水冷壁的热应力是否超限,具有重要意义。

Thermal Stress Analysis of Membrane Wall in Circulating Fluidized Bed Boiler

In order to study the thermal stress of circulating fluidized bed boiler membrane wall,the temperature,deformation and thermal stress of water wall at ceiling inflection point were analyzed by numerical simulation.The results show that the temperature gradient of the water wall changes greatly from the fire side to the back fire side,the deformation of the water wall is extremely uneven,and the stress concentration occurs at the contact between the water wall tube and the fin.After thinning,the maximum thermal stress first decreases and then increases,and then increases rapidly after the thickness is 1.5 mm.After the fin is worn and thinned,the thermal stress of the water wall increases gradually,and when the thermal stress exceeds the allowable stress of the material,it is easy to burst.When the thinning amount of water wall exceeds 21.4% of its own thickness,the water wall tube should be replaced.Fitting the law between the maximum thermal stress of water wall and the thinning amount of fins into a functional relationship is of great significance for judging whether the thermal stress of water wall exceeds the limit.