Turbine On-site Repair The Mobile Cnc Milling Structure Studies

As the important equipment in the thermal power, steam turbine with the large geometric size, operates under long period of harsh environments, such as high temperature, high pressure, which results in grooves in the joint surface easily caused by deflation; this seriously damages the safety of steam turbine. Currently the main approaches to repair the joint surface consist of manual grinding and brush plating, which are not only inefficient with long repairing cycle, but also difficult to assure the repairing quality. The steam turbine field repair mobile CNC milling machine is the ideal repairing tool for steam turbine and other large structures:a wide range of processing, efficiency, easy to ensure accuracy. Compared with the fixed milling machine, its greatest merit is the ability to assemble the modular machine components on site and adjust the processing datum to the optimal datum of the parts to be processed quickly according to the installation state of parts. Because of no domestic research of the milling machine at present, the machine performance must be in accordance with the design requirements at the drawing design stage. This paper takes steam turbine field repair mobile CNC milling machine as the research object, aiming at improving its processing precision and efficiency; the static and dynamics characteristics of the important components and whole machine are investigated by the FEA, and the design weaknesses of parts are also optimized; the analyzing results are verified by experiment in the end.The main research and conclusion are listed as follows:1-, A large-scale milling machine is developed according to the field repair needs of steam turbine. The static and dynamics characteristics are carried out for crossbeam,column and shaft by ANSYS, obtained the distribution of the SEQV and equivalent displacement, then the structural weakness are discussed according to modal result.2,Based on the modeling principle and method of bolted joint and guide joint, dynamic model of spring-damper element are built and characteristic parameters of the joint surface are identified. The static and dynamic results of the whole machine considered the joint characteristics are investigated to obtain the natural frequency and the corresponding vibration mode.3,Based on the previous analysis results of parts and the whole machine, it determines the parts to be improved:crossbeam,column. The optimization design of them are carried out by topology optimization and sensitivity analysis technology. The analysis results after optimization show that the whole machine static stiffness change obviously, the displacement reduce from the original 0.321mm to 0.177mm and the preceding six natural frequency are increased by 7.06%,38.36%,7.41%,6.28%,1.79%,10.1% respectively.4,In order to verify the correctness of the finite element model of the whole machine considered the joint characteristics, the compared results show the whole finite element model is rational after carrying out the natural frequency test.