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.