Vibration analysis method for dry frictional damping mistuned blades with tendons and shroud bands

Abstract

The invention discloses a vibration analysis method for dry frictional damping mistuned blades with tendons and shroud bands. The method comprises the steps of for actual mistuned states of the blades of a steam turbine, performing three-dimensional contact finite element analysis firstly to obtain support reactions of nodes of contact surfaces of the tendons and the shroud bands of the entire circle of the blades; secondly establishing a contact surface relationship by adopting spring damping units, considering positive pressures, areas and frictional coefficients at the spring damping units, and building a dry frictional damping mistuned vibration analysis model based on a Mindlin micro-sliding friction model and a harmonic balance method; thirdly considering a pre-stress and adopting harmonic response analysis for obtaining convergency values of vibration responses of the blades through iterative solving; and through cyclic calculation, obtaining vibration amplitude response curves of the dry frictional mistuned blades, and performing further extraction to obtain an inherent frequency and a vibration mode. The method is of important significance for dry frictional damping mistuned analysis of the blades and improvement of mistuned bladed disk vibration.

Description

【Technical field】 [0001] The invention belongs to the field of vibration analysis of steam turbine blades, and in particular relates to a vibration analysis method of dry friction damping detuned blades with tie ribs and shrouds. 【Background technique】 [0002] In the turbomachinery blisk system, detuning phenomenon often occurs due to manufacturing errors, material wear and other factors, and the vibration energy of the system is concentrated in a small number of blade areas, resulting in a much larger vibration response of the blade than other parts, resulting in vibration localization. Vibration localization increases the local blade stress and increases the risk of blade high-cycle fatigue damage. [0003] In the design of steam turbine blades, dry friction damping structure is often used to improve the stiffness and damping of the blades, so as to reduce the vibration level of the blades. The design of the long blade of the last stage of the steam turbine adopts the da...

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Problems solved by technology

The design of the long blade of the last stage of the steam turbine adopts the damping structure combining the ribs of the boss and the overall shroud. Since the contact dry friction damping force is nonlinear, compared with a single form of friction damping structure, no matter in the actual contact state or The friction damping process is more complicated

In the actual blisk system, due to factors such as installation and wear of the dry friction damping structure, the positive pressure load and the contact state of the contact surface of each blade tie and shroud are different, which will lead to detuning of the friction damping characteristics of the entire circle of blades. The difference between the actual friction damping effect and the analysis results of the coordinated blisk brings new difficulties to the research on the vibration characteristics of the blisk system and the design of the dry friction damping structure, so a mature and stable method is required to accurately obtain this Vibration response characteristics of a complex full-circle dry friction damped mistuned blade

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