| The supercritical air cooled steam turbine has the hot cycle efficiency to be high, saves the water resources and reduces massive waste water emissions. The supercritical air cooled steam turbine's research and development have the important meaning for realization energy conservation of the power plant. The 518mm leaf blade is designed for the air cooled 600MW steam turbine low pressure inferior last stage. This model leaf blade restores under the tendency with the aid of leaf blade's reverse forms the entire week self-locking damping connection structure. This leaf blade is the brand-new development, so the blade vibration characteristic relations unit's safety in operation. For the entire circle blade vibration frequency be able to avoid the resonance frequency scope in operation, the paper has carried on the detailed computation to the 518mm leaf blade resonance frequency. First uses the nonlinear finite element software's cyclic symmetry algorithm, established the impeller, the root, the airfoil, to the shroud ring forehead, to shroud ring body separately . These 5 sub models are assembled impeller-blade system model. Then using the hexahedron element mesh a great deal of modal analysis of the 518mm leaf blade was carried on for the different configuration type of shroud ring, the different thickness and the different rotational speed. According to leaf blade's sympathetic vibration frequency under different rotational speed, the Interlocked blade vibration Campbell chart was made and the leaf blade-impeller system sympathetic vibration frequency influence rule of the shroud ring form ,the shroud ring thickness under the steady work rotational speed was obtained. Finally through to the 518mm blade sympathetic vibration frequency calculation and the dynamic frequency test confirmation, the best Interlocked blade shroud ring's structure and the best thickness of the shroud ring were obtained finally, caused the new leaf blade design development work completes successfully.
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