Dynamic Characteristics Analysis and Structural Optimization for LP Casing of 600MW Steam Turbine
Aiming at the large vibration of the LP casing of a 600MW condensing steam turbine,the modal analysis of the LP casing structure is conducted using the three-dimensional finite element method.To simulate the rotating excitation of the LP rotor,a two-way simple harmonic force loading method is proposed.The forced vibration response of the LP casing is then determined through numerical calculations.A scheme for optimizing the structure is suggested through analysis of the findings,and the efficacy of this proposed scheme is assessed from various perspectives.The results demonstrate that the natural frequency falls close to 50Hz due to the low stiffness of the lower casing,and the rotor bearing support centre is a considerable distance from the end plate,causing a substantial excitation moment.These factors are the primary contributors to the large vibration of the LP casing.The proposed structural optimization scheme can improve the natural frequency of the LP casing,thereby keeping away from the 50Hz operating frequency,and also effectively reduce the amplitude of the vibration response.
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