Remanufacturing Design Of Fractured Blade Stage And Reconstruction Study Of Stages In Steam Turbine

Steam turbine is widely used in our country's electric power and industrial manufacture, and plays a very important role in the whole civil production. As important components, the blades running securely are one of important guarantees of a power plant's survival. Owing to the working environment very bad, the accidents of blades account for more than one third of one of the whole steam turbine accidents, among of which, blade fracture is the most familiar and serious.The performance of an extraction condensing steam turbine (ECST) in a power plant becomes bad after long-term operating, including the fracture accident of nearly one third length of moving blades in last stage. The broken blades are just truncated and finished simply by the plant, after being balanced dynamically, the unit then is brought into operation again, but the steam rate increases evidently and the performance becomes worse. In the case of mentioned above, based on the static strength calculation, the fracture reason was examined for the last stage moving blades, and the calculations revealed that the original blade design had shortage. The study was focused on redesigning the broken moving blade by means of three-dimensional design on the premise of satisfying the static strength requirement. Furthermore, by using commercial CFD (Computational Fluid Dynamics) software - NUMECA, the flow field was simulated and analyzed for both the last stage and the penultimate stage under the circumstances of unbroken and broken, so was it for the redesigned last stage. Detailed discussion was given to the influence of the broken blades on the performance of the whole stage, and feasible conclusions were drawn on the improved moving blades. It was shown that the redesigned moving blades produced a good performance under practical operation.Moreover, the capacity of the last two stages in an ECST is enlarged in this paper. Firstly, the new blade dimensions are determined after reconstruction with aerodynamic accounting routine. Secondly, the new blade is redesigned using modeling design method, and the intensity is verified. Finally, the new flow field is simulated with NUMECA, it is shown that the new blade is feasible and meets the requirements of reconstruction performance.