高低齿汽封表面换热系数计算方法研究

Research on calculation method of heat transfer coefficient of stepped seal surface

为探索汽轮机关键部件换热系数的计算方法,以某高压转子轴端高低齿汽封为例,对比分析了表面换热系数的4种常用经验公式,同时采用数值模拟方法研究了不同结构参数汽封的表面换热系数并得到拟合公式。结果表明:美国西屋公司、南京工学院-哈尔滨汽轮机厂和苏联采用的经验公式在结构上具有相似性,均与汽封间隙、汽封室高度、齿数、蒸汽导热系数和雷诺数相关。根据数值模拟结果得到的汽封表面换热系数与近壁面雷诺数和普朗特数正相关;换热系数呈周期性变化,在齿间隙出口处达到极值,且短齿出口处表面换热系数较大;当汽封间隙减小、汽封室高度或齿数增加时,换热系数减小;根据数值模拟结果得到的换热系数拟合公式,具有较好的适应性。拟合公式可用于叶顶汽封、隔板汽封、轴封等高低齿汽封表面换热系数的计算,同时该方法提供了一种计算大容量高参数汽轮机关键部件换热系数的思路,可为其设计和安全性校核提供依据。

In order to explore the calculation method of heat transfer coefficient of steam turbine key components,by taking the stepped seal at shaft end of a high-pressure rotor as an example,four commonly used empirical formulas for calculating the heat transfer coefficient of seal surface were analyzed,and the heat transfer coefficient of stepped seals surface with different structural parameters were studied by numerical simulation,and the fitting formula of heat transfer coefficient was obtained.The results show that,the empirical formulas used by Westinghouse,Nanjing Institute of Technology-Harbin Steam Turbine Plant and the Soviet Union are similar in structure,and both are related to parameters like seal gap,height of seal chamber,number of seal teeth,steam thermal conductivity and Reynolds number.The heat transfer coefficient of stepped seal surface is positively correlated with Reynolds number and Prandtl number near the surface.The heat transfer coefficient of the seal teeth surface changes periodically,reaching an extreme value at teeth gap exit,and the heat transfer coefficient of the short tooth exit surface is larger.The heat transfer coefficient decreases with the decrease of seal gap,the increase of seal chamber height and number of seal teeth.The fitting formula of heat transfer coefficient obtained according to the numerical simulation results has good adaptability.The fitting formula can be used to calculate the heat transfer coefficient of stepped seal surface,such as blade top seals,diaphragm seals,shaft end seals,and so on.Moreover,the method provides a way for calculating the heat transfer coefficient of key components of steam turbine with large capacity high-parameter,and provides a basis for design and safety check.