Study Of The Thermal Stress And Fatigue Life Of Steam Turbine Rotor

Due to the unit main components bear large temperature difference amplitude variation when the turbine power unit starts, stops or takes part in peak adjustment, the steam cylinder and rotor engender alternate thermal stress. The unit operation experience shows that, alternate thermal stress is a pivotal factor for the rate operating mode and the unit fatigue life. Since the turbine rotor bears complex multiaxial stress, to a certain extent, the low cycle thermal fatigue life of rotor can represent the whole unit life. So it has an important meaning to monitor the thermal stress and fatigue consume of the key components.The FEM method is utilized to analyse actual rotor transient temperature field for different operating mode. Based this foundation, The Indirect Couple FEM method is adopted to compute the transient stress field and obtain the dangerous cross section position used as monitoring emphasis and the transient thermal stress concentration coefficient. Finally the centrifugal force contribution for the equivalent stress is approached.Rotor-to-stationary rub is a serious malfunction in turbo-generator unit that may lead to catastrophe failure during operation. Since higher efficiency and higher parameter requirements lead to the reduction of clearances, the possibility of rotor-to-stationary rub increases. Thermal bending induced by rub plays an important role in the rotor dynamic characteristic, and can't be neglected. Rotor-to-stationary rub and the rub with thermal bending are analysed separately. The result shows that: the dynamic characteristic of rotor-to-stationary rub system considered with thermal bending is far different from the former.The alternate Thermal stress induces low cycle thermal fatigue damage. The Load History Fatigue Method is employed to analyse the low cycle thermal fatigue life, but this method founded on experiment and some theory bases can only obtain an approximate result, which may deviate from practice far and away. Furthermore, Continue Damage Mechanics (CDM) is adopted to analyse damage. The results from CDM model are compared with Equivalent Strain Method and Linear Damage Accumulation Theory.