Dynamic Response Analysis of Blades with Damping Structures of Shroud and Snubber

A method is developed to analyze the influence of friction structural damping on the vibration characteristics of turbine blades. Vibratory responses of a long steam turbine blade with shroud and snubber are studied. Finite element contact analysis of the steam turbine blades modeled in 3-D solid elements is conducted to obtain the normal contact force on the shroud contact surface and snubber contact surface of adjacent blades under a serious of different rotational speeds. The stiffness matrix elements and damping matrix elements are built between dry friction contact surface to simulate the frictional characteristics on the contact surface of damper and blade. The results show that with increases in rotational speed, the resonance amplitude decreases first and then increases when there is only shroud contact. The effects are similar when there are both shroud and snubber contact. Under the certain conditions, the increasing of excitation force can also degrade stiffness and damping of shroud and snubber.