火力发电机组汽缸温度场的二维模型

发电机组汽缸的结构比较复杂,汽缸壁比较厚,在机组启动过程中,其热应力及膨胀是影响机组机动性及运行安全的重要因素之一,而实现在线监测的关键在于汽缸温度场分布的计算。在圆筒壁导热的基础上,推导出汽缸内部蒸汽沿轴向按一定分布随时间非线性变化时,内壁为第三类边界条件、外壁为绝热条件的二维汽缸壁温度场分布的解析解。蒸汽温度非线性变化,对时间进行离散,给出了汽缸温度场的迭代公式,适用于汽缸温度场的在线监测。在相同加载及边界条件下对缸体进行了ANSYS有限元计算,有限元计算结果与推导公式计算结果吻合较好。所采用的推导方法和得到的温度场分布计算公式还适用于其它具有类似边界条件的厚壁圆筒部件的瞬态热分析。

Two-dimensional Temperature Model for Steam Turbine Cylinder Casing of Fossil-fired Units

Thermal stress and expansion of steam turbine casing are important factors affecting the flexibility and safety of steam turbine.The key of actualizing on-line monitoring is to calculate the temperature field of cylinder casing.A temperature field model of two-dimensional cylinder in transient condition is established.Its analytical solution is deduced in condition that the non-linear steam temperature distributes along axial direction and with adiabatic external wall and the third boundary internal wall.The iterative formula for on-line monitoring is obtained based on dispersing of time.The simulation for different cylinder casing is carried out with finite element calculation.A good coincidence is achieved compared with the calculation result of the theoretical model.The method can be applied to calculate the thermal state of other thick wall cylinder in transient condition.