Research On The Calculation Method Of Stiffness And Strength Of Large-size Condenser Tube Sheet And Its Software Developing

The condenser is one of the important auxiliary equipment of steam turbine.It was widely used in thermal power station and nuclear power station which is an important part of the steam turbine unit.The safety and reliability of the condenser is crucial to the whole unit safety,and the good water tightness of water side parts of condenser such as tube sheet,water box,tubes play an important role to ensure the safe and reliable operation of the condenser.In all of these parts,whether the stiffness and strength of tube sheet can satisfy the operating requirement largely determine the water tightness of condenser water side.It related to leakage problems of cooling water and the unit safety.At present,in china,the parameters which have already used in power station was adopted as the main references in designing the tube sheet and determining the tube sheet thickness and other important parameters based on practice experience.The tube sheet of large-size condenser is a perforated sheet.It contains tens of thousands of holes which were used to joint tubes through expanding and welding joint.Tube sheet extended as a flange connecting the water box with bolt,the shell connects tube sheet with expansion joint or integral connection.The stiffness and strength calculation of tube sheet involve the complex interaction between tube sheet,tubes,water box and shell,letting the tube sheet forces appeared more complex.Traditional design method is difficult to ensure that the stiffness and strength of tube sheet can meet the operating requirement and the well water tightness.Thus,the safe and stable operation of the condenser cannot be guaranteed.The structure of the condenser becomes more complex due to the enlargement of condenser.Therefore,it is imperative to research the tube sheet calculation method of large power plant condenser.This thesis combines the project of "Research on the calculation method of stiffness and strength of condenser tube sheet" commissioned by Dongfang Steam Turbine Co.,LTD,Dongfang Electric Group to research the stiffness and strength calculation method of large condenser tube sheet systematically and develop the specialized calculation software of tube sheet.The structure of large power plant condenser is complex,and lots of components have the direct applied forces with the tube sheet,and have different connection type.Reasonable assumptions of tube sheet loads was proposed based on considering the structural features adequately and the method of establishing the beam-strip mechanical model was ascertained according to the connection type of the shell and girder.The equation of end moment and other crucial loads of beam-strip mechanical model were deduced to make sure the main influence factor of end moment.The end moment is not only related to the end corner,but also influenced by the tube sheet thickness,materials,tube arrangement,tube length,elastic constant of tube and other parameters.The finite element method based on matrix displacement method was used to solve the mechanical model and the correctness and validity were proved by the case of standards for steam surface condenser of Heat Exchange Institute and the certification of finite element calculation procedure of ANSYS-APDL.According to the modeling and solving method for stiffness and strength calculation of large power plant condenser tube sheet,object-oriented software development platform VB.net was adopted to develop the specialized software for stiffness and strength calculation of condenser tube sheet of large power plant.The specialized software was used to calculate the tube sheet stiffness and strength of a 1000 MW nuclear power unit.The results indicated that the specialized software can satisfy the calculation requirement of condenser tube sheet of larger power unit,calculating quickly and efficient,and has good man-machine interactive performance.The correctness of modeling method for condenser tube sheet and the reasonability of using the simple support and 50 percent fixed boundary conditions to calculate were illustrated further by the comparison of the results of ANSYS-Workbench and specialized software calculating the same tube sheet.The problem of establishing the mechanical model of tube sheet stiffness and strength calculation and the solving method of the mechanical model was solved through the research in this paper.The specialized software has the characteristics of wide applicability,convenient and flexible which can improve the calculation speed greatly.It is significant to design the tube sheet especially the determination of the tube sheet thickness and other important parameters and also provides the reliable calculation software for stiffness and strength calculation of tube sheet.