Resonances Of Coupled Vibration Of Dry-friction Damper Turbine Blades

Blades is the heart of turbine, and it's credibility is responsibility for the safe of the tuibines and the whole power plant. One of the common structural failure of blades is due to excessive stresses caused by large amplitude vibrations. To reduce the vibratory stress of blades, the damped blades with integral wire or shroud are widely used by turbine works. As the vibratory energy is dissipated by the dry friction between the dampers, the vibration of blades is reduced. The dynamic characteristics of dry friction damped blades will be discussed in this paper.Part one, introduction and analysis of the damped mechanism and the excitation force of turbine blades.The comprehensive analysis of the damped mechanism and the excitation force on dry-friction damper are summarized in this paper, and the model of dry-friction is point out.Part two, dynamics of the one-dof model. According to the fact that the friction includes four intervals where the system possesses a different linear vibration characteristic,Fourier Method is used to convert it to a smooth curve. Then, the model is studied by the average method. The influences of the system parameters on the amplitude- frequency curves are discussed.Part three, dynamics of the two-dof model.The coupling of flexion-torsion, the two-dof blade model is studied here. Then, the model is studied by the average method in two stable and nonstable situations. The results in this paper show that the dry friction in blades plays a very important role in reducing vibration amplitude of the blades. The normal force between the rubbing surfaces can influence the damping effect of blades. Through the study we found that there is an optimum value for the normal force, under which the vibration of blades can be damped effectively. The damped blades is a nonlinear dynamic system, so its natural frequency can be influenced by external force. Besides, the influence of shear stiffness of rubbing surfaces, the place of the damper on the blades, and the friction coefficient on dynamic characteristics of blades are also discussed.