Abstract
In turbomachinery bladed disks are typical cyclic symmetric structures where high-cycle fatigue of the blades can easily occur. Increasing the shroud structure is an effective blade vibration reduction method using the dry friction of the shroud contact surface to dissipate vibration energy. During one vibration cycle of the blade, the contact surface of the shroud may have one or several states of stick, slip, and separation due to the different amplitude of blade, which affects not only the damping, but also the stiffness of the system. This paper proposes a method to analyze the damping characteristics of blades with shroud considering the change of equivalent contact stiffness of the shroud by using the finite element method. With a 2D contact model, this method calculates the equivalent damping and obtains the damping characteristic curve to evaluate the damping of shroud. During the design phase, the objective is that when resonance occurs, the shroud can provide the optimal damping ratio under the allowable vibration stress of the blade. The parameter sensitivity of the damping characteristic for one bladed disk with parallel shroud is investigated. It is shown that vibration phase angle, contact stiffness, contact force, friction coefficient significantly influence the damping characteristics.
Highlights
Turbine rotor blades in aero-engines are subjected to high centrifugal loads, static stresses caused by thermal loads, and vibration stresses caused by varying loads, which are likely to cause high-cycle fatigue (HCF) of the blades
The matrix 27 elements are established between several pairs of nodes on the contact surface of the shroud, and their stiffness value are the contact stiffness, and the prestress modal analysis is carried out, which can be directly calculated with the help of commercial software, such as ANSYS®
Contact model with variable normal force is adopted, and the bine blades isofproposed, which takesratio intowith account thestress variation of thebycontact equ the relationship the equivalent damping vibration is calculated the influence of separation state on equivalent stiffness is considered
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In order to describe contact more effectively, Cameron and Griffin [13] prop reduced order models (ROM) suitable for different situations to calculate the nonlinear ternating frequency-time where mode after converting the frequency domain displ forced response [14,15,16], such (AFT), as component synthesis (CMS). The goal in design stage is to provide greater damping ratio under vibration by an equivalent linearization method [21] and rub-dynamic character macroslip friction model [22] of bladed disks were studied. Symmetry 2021, 13, 413 the allowable vibration stress of the blade In this method, the equivalent damping ratio is calculated by the proportional relationship between friction energy consumption and the max vibration kinetic energy of the bladed disk. The suggestions in the design stage are given, and the parameter sensitivity analysis of damping characteristics is carried out from four aspects: normal and tangential vibration phase angle, contact stiffness, initial contact force and friction coefficient
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