三偏心蝶阀热棘轮效应的数值模拟

Numerical Simulation of Thermal Ratcheting of Triple Eccentric Butterfly Valve

为了探讨热棘轮效应对三偏心金属硬密封蝶阀密封副热变形及密封性能的影响,先排除了蝶阀发生塑性垮塌失效、密封结构在数次常温与高温交变循环载荷作用下发生疲劳失效的可能性,然后通过ANSYS Workbench有限元分析软件对三偏心蝶阀进行常温与高温交变循环载荷下的热棘轮效应研究,基于Chaboche非线性随动强化模型对三偏心蝶阀进行10次温度循环加载分析。结果表明:高温工况下阀座内环面与阀体外壁面的最大温差约为60℃,温度降低到常温后阀座的最大塑性应变随循环次数的增加出现渐增性塑性累积;10次温度循环后阀座的最大塑性应变为0.02116,阀座在温度循环载荷的作用下发生热棘轮效应;在第5次温度交变循环之后,阀座与密封圈的最大径向变形分别为0.2844 mm和0.2753 mm;阀座的最大径向变形大于密封圈的最大径向变形,阀座的残余变形导致密封面出现间隙,证明三偏心蝶阀出现密封失效现象是由于阀座发生热棘轮效应导致的。对阀体外壁面进行良好保温后,经有限元计算阀座未发生棘轮效应,可见对阀体进行良好保温是避免因阀座发生棘轮效应而出现密封失效的有效手段。该研究结果揭示了蝶阀在数次常温与高温交变循环载荷作用下出现密封失效的原因,并提出相应的防范措施。这对相同工况下的其他类型阀门和压力管道等设备避免发生热棘轮效应具有十分重要的指导意义。

In order to study the effect of thermal ratcheting on the thermal deformation and sealing performance of the triple eccentric metal hard seal butterfly valve,this paper firstly excluded the possibility of plastic collapse failure of the butterfly valve and fatigue failure of the sealing structure under several alternating cyclic loads at room temperature and high temperature.ANSYS Workbench finite element analysis software was adopted to study the thermal ratcheting effect of the triple eccentric metal hard seated under alternating cyclic loading at room and elevated temperature,and ten times of temperature cyclic loading analysis were performed on the butterfly valve based on Chaboche nonlinear kinematic hardening model.The results show that the maximum temperature difference between the inner ring surface of the valve seat and the outer wall of the valve body is about 60℃under high temperature conditions.After the temperature is reduced to room temperature,the maximum plastic strain of the valve seat increases with the increase of cycle times.The maximum plastic strain of the valve seat after 10 temperature cycles is 0.02116,and the thermal ratcheting effect occurs under the action of temperature cyclic load.After the fifth temperature alternating cycle,the maximum radial deformation of the valve seat and the sealing ring is 0.2844 mm and 0.2753 mm respectively.The maximum radial deformation of the valve seat is greater than that of the sealing ring.The residual deformation of the valve seat leads to the gap of the sealing surface,which proves that the sealing failure of the triple eccentric butterfly valve is caused by the thermal ratchet effect of the valve seat.After applying good thermal insulation on the exterior wall of the valve body,the ratcheting effect of the valve seat does not occur according to finite element calculation,indicating that good thermal insulation on the valve body is an effective means to avoid sealing failure caused by ratcheting effect of the valve seat.The research results reveal the reasons for the sealing failure of the butterfly valve under several alternating cyclic loads at room temperature and high temperature,and this paper puts forward corresponding preventive measures,which is of great guiding significance for other types of valves and pressure pipelines under the same working conditions to avoid thermal ratcheting effect.