| The gas turbine which belongs to the representative of the complex rotating machinery is an integration of multiple technologies of high technology product. Since the blade which leads the most accidents is one of the critical component of gas turbine, its performance directly affects the security and stability of the turbine. According to statistics, the damaged blades lead to70%the forced outage rate in the United States of America power plant steam turbine and the accidents caused by blades often account for about half of the total losses. So it is necessary to study the dynamic characteristics of rotor blade and to improve gas turbine’s performance, durability, reliability and life, to avoid accidents and economic losses caused by the damaged blades, which has an important engineering value.In this paper, the natural characteristics and vibration response of blade are studied and analyzed comprehensively by using the numerical analysis methods such as three-dimensional finite element (FEA) method, cyclic symmetry method, contact analysis, prestressed modal analysis.At the beginning, the contact tenon and tenon groove is considered to study on natural characteristics of the blade-disc coupling system which is cyclic symmetry structure, and the natural frequencies and the corresponding vibration modes are obtained. The influence on blade vibration are analyzed because of the coupling effect between the blade and disc; In order to research the natural characteristics of blade-disc coupling system, the Campbell diagram is drawn by using the calculation results and then the resonance speeds are calculated. In this way, the necessary theoretical basis is provided for further study on the design optimization and vibration security of blade-disc coupling system.Then, the dynamic response of rotating blade is studied under the blade-casing’s rub-impact. Based on the characteristics of blade-casing’s rub-impact, a rubbing force model is proposed:a half sine pulse vibration force is simplified as a rubbing force generated by the process of blade-casing rub-impact and the parameters of the pulse excitation force are determined. The transient responses of the rotating blades are analyzed in three working conditions of slight rubbing, moderate rubbing and serious rubbing. And then the influence of rubbing degree on the rotating blades’displacement response and dynamic stress are compared.Finally, the blades forcing response under the stator-rotor wake influence are studied. By using the surface effect element to transform the results of three-dimensional unsteady flow to the load steps which can be loaded directly on the structural finite element model, the numerical calculation method is achieved to convert the flow filed calculation results to structure domain; The response of blades’displacement and the maximum equivalent stress are researched under the stator-rotor wake influence. |
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