Research On The Deformation And Creep Life Of The High Temperature Parts Of Steam Turbine Of The Thermal Generating Unit

In China, coal was the major one time resource, the installed gross capacity of thermal generation was over 75 percent of the installed gross capacity of the whole nation, and the gross generation of thermal generation was over 80 percent of gross generation of the whole nation. The safety operation of thermal generating units is important to industry development and the people's livelihood. High parameter, large capacity and automatization demand not only for electrical grid but also for power generating units will become a tendency in order to increase economics. To ensure the stability of electrical grid running the Automatic Generation Control technology has to be improved. To improve automatic generation control and to realize on-line monitor have the great significance in theory and practical application. The steam turbine is one of the most important parts in thermal generating units. This work is involved in the deformation and creep life of the high temperature parts of steam turbine.An equivalent coefficient of convective heat transfer was defined. Based on heat transfer differential equation for cylinder, two dimensional transient analytical solution along radial and axial direction with respect to the boundary conditions of outer and inner wall with third type non-homogeneous temperature boundary is achieved, which can be used in on-line temperature monitoring system for the steam turbine casing. In order to demonstrate the expansion ability of irregular finite sub-structure, a new characteristic value, called expansion characteristic temperature, is defined. And an appropriate algorithm which can be used to calculate the deformation of different parts is also proposed. Owing to such a definition, it is possible to evaluate deformation between casing and rotor.The Axial deformation Margin was defined. The value of the axial deformation margin was calculated on-line, which was used to control the steam temperature changing rate. It ensured the faster start-up of steam turbine with allowable axial deformation. And it improved the operation safety of the grid and the power stations. The axial deformation on-line monitor and automatic changing temperature-speed control system was closed loop control.Using UPFs (User Programming Features) of ANSYS, the creep of notched bar under high temperature was implemented based on the experimental data of uniaxial and multiaxial specimen. The stress redistribution in the throat cross section of the notch induced by high-temperature multiaxial creep and the creep control stress- Equivalent Skeletal Stress (ESS) were founded. The rupture time of the multiaxial creep was estimated according to the uniaxial creep life curve or the rupture life equation based on ESS. The relationship of the skeletal stress and the notch geometry has been established.Creep damage model was improved by inducting strain threshold value based on Norton-Kachanov creep model, which was more exact to describe creep process. Creep behavior of bolt was simulated by reworking ABAQUS subroutine based on improved creep damage model. It is indicated that creep rupture of bolt is not taking place at screw thread where the stress concentrated, but taking place at the position of screw shaft. A good coincidence comparing the result calculated according to the theoretical model presented in this paper with finite element calculation can be observed.