Steam Turbine Rotor Damage Analysis And Startup Process Optimization Study

Gas-steam combined cycle power generation has developed rapidly in recent years due to its advantages of high efficiency and low pollution.Steam turbines are important equipment in power plants.During start-stop process and rated operation of the unit,alternating stress fatigue and high-temperature creep effects have great impacts on the strength and service life of the rotor,which is the key component of the turbine.It is necessary to analyze and calculate the damage during the use of the rotor,and optimize and improve the existing turbine start-up process to meet the safety requirements of the unit while meeting the peak-shaving performance of the unit.In this paper,the steam turbine in a combined cycle unit is taken as the research object.A two-dimensional axisymmetric finite element model of the rotor is established,and the temperature and stress distribution of the rotor during the typical startup process and rated steady operation are solved.Combined with the related theory of continuous damage mechanics,the damage of the rotor under the interaction of fatigue and creep is calculated,and is compared with the results obtained by the linear damage accumulation law.It is found that the interaction effect of fatigue caused by different stress levels and the coupling effect of fatigue-creep will exacerbate the rotor damage.The nonlinear damage accumulation law can describe the rotor damage cumulative process more reasonably than the linear damage accumulation law.By adjusting the heating and load-raising methods,the existing unit startup process is improved and optimized.In order to improve the optimization efficiency,save trial calculation time,and enhance the rationality of the optimization plan selection,this study writes an optimization program,sets a certain parameter range to change the load and steam temperature rise rate and warm-up time,solves the rotor temperature field and stress field cyclically,and compare the temperature and stress changes in the critical area of the rotor in various schemes.According to various optimization goals of reducing stress,speeding up startup,and both,various optimization schemes suitable for each situation are proposed.The multi-objective start-up optimization scheme has good flexibility.During unit peak-shaving operation,the schemes that can shorten the start-up time and increase benefits are able to be chosen more.As the performance of the material deteriorates,the schemes with less stress during the starting process and longer rotor life can be selected.This can meet the diverse start-up requirements of the unit,obtain more economic benefits and ensure the safe operation of the unit.