温度梯度对金属波纹管力学性能影响分析

高温熔盐调节阀中金属波纹管是保证其正常运行的重要部件,波纹管外侧被熔盐介质包围,承受外压、轴向位移及高温载荷,且波纹管轴向存在较大温度梯度,为调节阀中薄弱元件。本文应用有限元软件ANSYS,材料模型选择理想塑性材料模型,计算单元为热固耦合单元,对比分析了U形和V形波纹管在各设计工况下的应力分布,结果表明,位移载荷是两种波纹管失效的主要原因。位移载荷在两种波纹管中引起的应力大小基本一致,但V形波纹管在设计压力、温度载荷作用下的应力显著小于U形,故调节阀中使用波纹管类型选择为V形。此外,对V形波纹管在多工况下的应力分布、塑形应变及极限位移载荷进行了计算,对比分析了设计温度载荷、阀体存在保温层时温度载荷及常温温度载荷对波纹管的影响,结果显示,高温下波纹管极限位移载荷约为常温的三分之一,但阀体外部添加保温层,虽然使得波纹管温度升高,但对波纹管极限压缩载荷影响并不大。

Effect Analysis of Temperature Gradient on Metal Bellow Mechanical Performance

The bellow in molten salty control valve is essential to ensure the valve safe operation. Surrounding by molten salt, the control valve bellow loads external pressure,axial displacement and high temperature with large temperature gradient, which is error-prone part. In this paper,U-shape and V-shape bellows mechanical performances have been compared by means of ideally plastic material model and structural-thermal coupling element in ANSYS. Results show that axial displacement load is the main reason for bellows failure,and stress magnitude remains the same in both structures,while,stress in V-shape bellow is much smaller than U-shape bellow under the same pressure and temperature,so V-shape bellow has been chosen for molten salty control valve. In addition,a study on stress distribution,plastic strain and limit displacement load have been carried out under multiple temperature gradients, which is design temperature load,temperature load when the valve is covered with heat preservation and room temperature. As can be seen from the results,limit displacement load under high temperature is only equivalent to one-third compared with limit load under room temperature, and heat preservation has little effect on bellows limit displacement load even though temperature on bellow has increased.