Under deep peak shaving and variable operating conditions of thermal power units

significant changes in steam temperature have caused a significant increase in thermal stress in some structures of the units

which accelerated structural damage

and resulted in frequent safety accidents. To solve these problems

by taking the regulating stage rotor of a 300 MW steam turbine as the object

and Ansys software is used to analyze the thermal stress

aerodynamic force

and centrifugal force of the blades. Firstly

structural optimization is carried out on root of the blade to significantly eliminate the unreasonable local stress concentration phenomenon commonly found in conventional calculations. Then

the distribution laws of temperature and stress fields in the regulating stage under different conditions such as steady-state and transient during the deep peak shaving process of thermal power units are revealed. Moreover

the effects of the temperature and stress fields on safety performance of the unit are also investigated. The results indicate that

the maximum equivalent stress increases by about 24% under steady-state conditions with temperature difference of different nozzle groups of 50 ℃. The transient load increase rate of 5% THA/min is about three times higher than that of 2% THA/min

causing low cycle fatigue damage to the rotor. Compared with steady-state operating conditions

increasing the load once a day at a rate of 2% THA/min from half load to full load increases the overall damage by about 38%.