疏水扩容器接管与壳体连接处热应力计算分析

Thermal Stress Calculation and Analysis of Nozzle Connections of Drain Flash Tanks

为避免流体温度突然升高引起疏水扩容器接管与壳体连接处产生过大的瞬时热应力,造成安全事故,以某一300MW机组主蒸汽疏水集管为研究对象,分别采用传统算法和ANSYS-Workbench有限元软件对接管与壳体连接处产生的瞬时热应力进行了强度计算校核。结果表明:在所研究工况范围内,连接处的最大瞬时热应力发生在接管与壳体连接的内表面;在接管与壳体连接处内表面倒圆角,可以有效减小瞬时热应力,避免安全事故发生;当主蒸汽温度在500℃以上时必须对接管与壳体连接处内表面倒圆角,且倒圆半径不小于6mm;建议对于主蒸汽温度在300℃以上的接管内部也进行倒圆。研究结果可以为疏水扩容器的强度设计校核提供理论支持和研究方法。

In order to avoid failures caused by extra thermal stress under sudden temperature raise in the nozzle connections of drain flash tanks,for a main steam drain piping of 300 MW unit,the thermal stress of the nozzle connections was calculated using the traditional method and finite element analysis software ANSYS-Workbench respectively.The results showed that in the research scope,the maximum transient thermal stress emerged at the inner surface of nozzle connection,and the stress could effectively be reduced by chamfering at this part.It is indicated that when the steam temperature is above 500℃,it is necessary to chamfer the inner surface at nozzle connection with the chamfer radius no less than 6 mm.Meanwhile,chamfering at inner connection is also recommended when the main steam temperature is higher than 300℃.The research results can provide theoretical support and research methods for the strength design and check of drain flash tanks.