Numerical Analysis And Investigation Of Low Cycle Fatigue And High Temperature Creep Life Damage For Steam Turbine's High Pressure Rotor

Because of gradually increasing of Peak-Valley difference and total amount of power load in the modern power system, the thermal power unit with high parameters and large capacity will be inevitably participated Peak Regulation in future. So the steam turbine unit must be quickly start-stop in order to meet the needs of power network, and this can reduce heat loss and make the unit operation be more economic. Contradictorily, unit fast start-stop will inevitably make generating equipment subjected thermal shock and increase the unit lifespan loss, which is very unreasonable and unsafe. Therefore we must strengthen management of the turbine life expectancy to ensure the thermal power generation units operating safely and economically.According to the actual conditions of the steam turbine rotor life management, this article investigated on 300MW steam turbine power plant, and the temperature field and stress field in the steam turbine under cold start-up and hot start-up condition were calculated by ALGOR finite element analysis software. Basing on the calculation results, the life of the rotor was further calculated, and according to the fatigue mechanism of metal materials, the hardness changes caused by aging was corrected during calculation, and the coupling calculation between fatigue creep loss were researched. After comprehensive analysis and calculation, reasonable suggestions for turbine rotor life management were put forward. The main job included:(1)the finite element calculation principle of rotor temperature and stress field was researched, then the computational geometry model was determined, after simplifying the model and dividing grid,the grid at the stress concentration parts was refined.(2)The temperature field and stress field in the steam turbine under cold start-up and hot start-up condition were calculated by ALGOR finite element analysis software, and according to the results, researchers analyzed the thermal stress suffered by rotor and investigated the effect of temperature rising rate when the unit started on the thermal stress and life loss of rotor.(3)The performance index of materials hardness was introduced by studying on the fatigue life theory, and according to the practical operation mode of units, the relationship between material hardness and fatigue life loss ,creep life loss, and the effects on the unit life loss were analyzed.(4)Because the units operated in severe environments of high temperature and pressure for long time, materials hardness of the rotor must be weakened. According to the analysis of the relationship between material hardness and fatigue life loss and creep life loss, It is very significant for the unit safe operation to calculate the fatigue life loss and creep life loss resulting from alternating stress basing on the actual changes of materials hardness value during the rotor operation.(5)The temperature rising rate made great effect on the rotor thermal stress and life loss of unit during the start-up process. The lifespan wastage of unit was reduced by adjusting the temperature rising rate when the rotor materials hardness changed.