Abstract: Reducing thermal stress of rotor during steam turbine start-up and shutdown process is very important for preventing the initiation and propagation of crack in rotor due to thermal fatigue. The finite element method is employed to calculate the transient temperature field of the high-intermediate pressure rotor of a 660 MW steam turbine. An elastic-plastic finite element model is used to determine the transient stress and strain field. The effect of temperature rising distribution on the thermal stress of rotor during steam turbine start-up is investigated. Calculated results show that the maximum thermal stress of rotor is reduced by thirty four percent than before by using different temperature rising model in the same period of start-up. It can be concluded that the appropriate model of the temperature rising during start-up could effectively reduce the thermal stress of the rotor, also shorten the start-up period. The conclusion drawn can be referenced for determining the reasonable curve of start up for steam turbines.

Key words: Rotor, Steam turbine, Temperature rising distribution, Temperature rising rate, Thermal stress