孔板管道流动加速腐蚀受温度影响的数值模拟

Numerical simulation of effect of temperature on flow accelerated corrosion in orifice pipeline

电厂汽水管道的运行中,流动加速腐蚀(FAC)普遍存在且威胁着管道系统。为很好预测电厂管道流动加速腐蚀,本文基于电厂管道实际工况,采用流体动力学软件根据温度变化相应地调整水的物性参数,模拟了孔板管道下的流场,观察高速及高湍流动能分布区域,模拟计算得到不同温度下溶解度、速度、壁面剪切力及传质系数的变化,并结合流动加速腐蚀预测模型更精确地分析了温度对流动加速腐蚀的影响。结果显示:温度通过影响速度及黏性系数,进一步影响到壁面剪切力及传质系数,最终影响到FAC速率;传质系数与溶解度均受温度影响,在150℃以下,温度对FAC速率的影响显著且主要是通过传质系数实现的;FAC速率在Z/D≈0.7~1.0达到峰值,在Z/D≈3.8~4.3出现第二峰,这两处为孔板管道高危腐蚀区域。

In the operation of steam pipe of power plant,flow accelerated corrosion(FAC)is widespread and threatens the pipeline system.In order to predict the accelerated corrosion of power plant pipelines,the subject is based on the actual working conditions of power plant pipelines.The fluid dynamics software is used to adjust the physical parameters of water according to the temperature change,simulate the flow field under the orifice pipe,and observe the high speed and high turbulence.In the kinetic energy distribution region,the changes of solubility,velocity,wall shear force and mass transfer coefficient at different temperatures were simulated and compared with the flow accelerated corrosion prediction model to more accurately analyze the effect of temperature on flow accelerated corrosion.The results show that the temperature affects the wall shear force and mass transfer coefficient,and finally affects the FAC rate.The mass transfer coefficient and solubility are affected by temperature.Below 150℃,the effect of temperature on the FAC rate is significant and mainly achieved by mass transfer coefficients;the FAC rate peaks between Z/D≈0.7—1.0,and the second peak appears between Z/D≈3.8—4.3,which is the high-risk corrosion area of the orifice tube.