Optimization of Interblade Friction Damper Design

2000 ◽  
Author(s):  
Lars Panning ◽  
Walter Sextro ◽  
Karl Popp
Keyword(s):  
Equations Of Motion ◽  
Turbine Blades ◽  
Relative Displacement ◽  
Contact Forces ◽  
Hertzian Contact ◽  
Computation Method ◽  
Friction Damper ◽  
Friction Dampers ◽  
Advantages And Disadvantages ◽  
Bladed Disk

The vibration amplitudes of bladed disk assemblies can be reduced significantly by means of friction damping devices such as shrouds, damping wires and interblade friction dampers. In practice, interblade friction dampers are applied in rotating arrangements with various geometries showing curved or flat surfaces like so-called wedge-shaped dampers. This paper is focusing on a computation method to predict the dynamical behaviour of turbine blades with friction dampers including both, curved and wedge-shaped dampers with Hertzian and non-Hertzian contact conditions, respectively. The presented computation method uses a 3D contact model to calculate the contact forces, including normal and tangential stiffnesses, roughness and microslip effects. The relative displacements in the contact area can be expressed by means of 6 DOF of the blade platforms and 6 rigid body DOF of the damper including translational and rotational displacements. The relative displacement of the friction damper with respect to the adjacent blades can be derived from the contact kinematics of the blade-damper-blade system and the equations of motion of the friction damper. Thus, the model can be applied to investigate spatial motions of the bladed disk assembly including bending and torsional vibrations. A comparison of different friction damper designs with respect to an optimal damper geometry and damper mass is presented. The advantages and disadvantages of each design will be discussed. Experimental results are shown to validate the developed computation method.

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

Equivalent Linearization of Bladed Disk Assemblies with Friction Nonlinearities Under Random Excitation

2020 ◽  
Author(s):  
Alwin Förster ◽  
Lars Panning-von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Degrees Of Freedom ◽  
Turbine Blades ◽  
Random Excitation ◽  
Linearization Method ◽  
Equivalent Linearization ◽  
Friction Damper ◽  
Bladed Disk ◽  
Stationary Stochastic Processes ◽  
Bladed Disk Assembly ◽  
Equivalent Linearization Method

Abstract The present article addresses the vibrational behaviour of bladed disk assemblies with nonlinear shroud coupling under random excitation. In order to increase the service life and safety of turbine blades, intense calculations are carried out to predict the vibrational behaviour. The use of friction dampers for energy dissipation and suppression of large amplitudes makes the mechanical system nonlinear, which complicates the calculations. Depending on the stage, different types of excitation can occur in a turbine, from clearly defined deterministic to random excitation. So far, the latter problem has only been dealt with to a limited extent in the literature on turbomachinery. Nevertheless, there are in general different approaches and methods to address this problem most of which are strongly restricted with regard to the number of degrees of freedom. The focus of this paper is the application of an equivalent linearization method to calculate the stochastic response of an academic model of a bladed disk assembly under random excitation. The nonlinear contact is modelled both with an elastic Coulomb-slider and a Bouc-Wen formulation to reproduce the hysteretic character of a friction nonlinearity occurring in the presence of a friction damper. Both the excitation and the response are limited to mean-free, stationary stochastic processes, which means that the stochastic moments, do not change over time. Unlike previous papers on this topic, the calculations are performed on a full bladed disk assembly in which each segment is approximated with several degrees of freedom.

A Resonance Tracking Algorithm for the Prediction of Turbine Forced Response With Friction Dampers

2000 ◽  
Author(s):  
C. Bréard ◽  
J. S. Green ◽  
M. Vahdati ◽  
M. Imregun
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Case ◽  
Friction Damper ◽  
Blade Vibration ◽  
Frequency Shifts ◽  
Friction Dampers

This paper presents an iterative method for determining the resonant speed shift when non-linear friction dampers are included in turbine blade roots. Such a need arises when conducting response calculations for turbine blades where the unsteady aerodynamic excitation must be computed at the exact resonant speed of interest. The inclusion of friction dampers is known to raise the resonant frequencies by up to 20% from the standard assembly frequencies. The iterative procedure uses a viscous, time-accurate flow representation for determining the aerodynamic forcing, a look-up table for evaluating the aerodynamic boundary conditions at any speed, and a time-domain friction damping module for resonance tracking. The methodology was applied to an HP turbine rotor test case where the resonances of interest were due to the 1T and 2F blade modes under 40 engine-order excitation. The forced response computations were conducted using a multi-stage approach in order to avoid errors associated with “linking” single stage computations since the spacing between the two bladerows was relatively small. Three friction damper elements were used for each rotor blade. To improve the computational efficiency, the number of rotor blades was decreased by 2 to 90 in order to obtain a stator/rotor blade ratio of 4/9. However, the blade geometry was skewed in order to match the capacity (mass flow rate) of the components and the condition being analysed. Frequency shifts of 3.2% and 20.0% were predicted for the 1T/40EO and 2F/40EO resonances in about 3 iterations. The predicted frequency shifts and the dynamic behaviour of the friction dampers were found to be within the expected range. Furthermore, the measured and predicted blade vibration amplitudes showed a good agreement, indicating that the methodology can be applied to industrial problems.

Investigation of Damping Potential of Strip Damper on a Real Turbine Blade

2016 ◽  
Author(s):  
M. Afzal ◽  
I. Lopez Arteaga ◽  
L. Kari ◽  
V. Kharyton
Keyword(s):  
Boundary Conditions ◽  
Dynamic Properties ◽  
Equations Of Motion ◽  
Iterative Solution ◽  
Element Model ◽  
Forced Response ◽  
Contact Forces ◽  
Response Analysis ◽  
Bladed Disk ◽  
Different Types

This paper investigates the damping potential of strip dampers on a real turbine bladed disk. A 3D numerical friction contact model is used to compute the contact forces by means of the Alternate Frequency Time domain method. The Jacobian matrix required during the iterative solution is computed in parallel with the contact forces, by a quasi-analytical method. A finite element model of the strip dampers, that allows for an accurate description of their dynamic properties, is included in the steady-state forced response analysis of the bladed disk. Cyclic symmetry boundary conditions and the multiharmonic balance method are applied in the formulation of the equations of motion in the frequency domain. The nonlinear forced response analysis is performed with two different types of boundary conditions on the strip: (a) free-free and (b) elastic, and their influence is analyzed. The effect of the strip mass, thickness and the excitation levels on the forced response curve is investigated in detail.

The Interaction Between Mistuning and Friction in the Forced Response of Bladed Disk Assemblies

1985 ◽  
Vol 107 (1) ◽  
pp. 205-211 ◽  
Author(s):  
J. H. Griffin ◽  
A. Sinha
Keyword(s):  
Gas Turbine ◽  
Turbine Blades ◽  
Forced Response ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Resonant Response ◽  
Friction Dampers ◽  
Bladed Disk ◽  
The Impact ◽  
Slip Force

This paper summarizes the results of an investigation to establish the impact of mistuning on the performance and design of blade-to-blade friction dampers of the type used to control the resonant response of turbine blades in gas turbine engines. In addition, it discusses the importance of friction slip force variations on the dynamic response of shrouded fan blades.

Experimental Study of Dynamic Characteristics of Dry Friction Damping of Turbine Blade Steel

2013 ◽  
Vol 690-693 ◽  
pp. 1979-1982 ◽  
Author(s):  
Peng Fei Zhao ◽  
Qiang Zhang ◽  
Jun Wu ◽  
Di Zhang
Keyword(s):  
Dry Friction ◽  
Turbine Blades ◽  
Initial Pressure ◽  
Relative Displacement ◽  
Radius Of Curvature ◽  
Response Analysis ◽  
Friction Damper ◽  
Friction Damping ◽  
Stick Slip ◽  
Dry Friction Damping

For lot of structures, especially turbine blades, damper can dissipate the vibration energy by friction. Investigating the property of metal dry friction damping can give many usable data for response analysis of damping blade which is important in damped blade designs. The paper constructs an experimental rig and carries out experiment with pieces having radius of curvature 6mm, 12mm and 24mm. The relative displacement between contact surfaces and the friction force changed with time were obtained for different initial pressure and frequency of exciting force. Hysteresis curves of dry friction damper were derived. The variations of friction coefficient of stick-slip area, equivalent stiffness and equivalent damping were calculated based on experimental data.

Experimental Identification of the Nonlinear Parameters of an Industrial Translational Guide

2006 ◽  
Author(s):  
Jaspreet Dhupia ◽  
Bartosz Powalka ◽  
A. Galip Ulsoy ◽  
Reuven Katz
Keyword(s):  
Relative Velocity ◽  
Relative Displacement ◽  
Force Function ◽  
Hertzian Contact ◽  
Design Stage ◽  
Restoring Force ◽  
Weakly Nonlinear ◽  
Advantages And Disadvantages ◽  
Nonlinear Restoring Force ◽  
Receptance Coupling

Prediction of machine dynamics at the design stage is a challenge due to lack of adequate methods for identifying and handling the nonlinearities in the machine joints, which appear as the nonlinear restoring force function of relative displacement and relative velocity across the joint. This paper discusses identification of such a nonlinear restoring force function for an industrial translational guide for use with the Nonlinear Receptance Coupling Approach (NLRCA) for evaluating machine dynamic characteristics. Translational guides are among the most commonly used joints in machine tools. Both a parametric and nonparametric technique has been employed to identify the nonlinearities. A novel parametric model based on Hertzian contact mechanics has been derived for the translational guide. This model includes the effect of joint geometry, material properties and preload. A nonparametric method based on two-dimensional Chebyshev polynomials is also used. The models derived from the two techniques, i.e., parametric and nonparametric, are fitted to the experimental data derived from static and dynamic tests to get the restoring force as a function of relative displacement and relative velocity across the joint. The resulting joint model exhibits a weakly nonlinear stiffness term and a viscous damping term. The results from both techniques are compared in the frequency domain. The advantages and disadvantages of parametric and nonparametric techniques are also discussed. The design of experiments for evaluating the nonlinearities in such industrial machine tool joints is a challenge, requiring careful alignment and calibration, because they are typically very stiff. This constrains the dynamic experiments to be carried out at high frequencies (e.g. 2000-7000Hz) where the experimental readings are very sensitive to errors in geometry and calibration.

Harmonic Balance Vibration Analysis of Turbine Blades With Friction Dampers

1997 ◽  
Vol 119 (1) ◽  
pp. 96-103 ◽  
Author(s):  
K. Y. Sanliturk ◽  
M. Imregun ◽  
D. J. Ewins
Keyword(s):  
Harmonic Balance ◽  
Turbine Blades ◽  
Numerical Test ◽  
Harmonic Balance Method ◽  
Nonlinear Behavior ◽  
Friction Damper ◽  
Friction Dampers ◽  
Equivalent Time ◽  
Time Marching ◽  
Detailed Assessment

Although considerable effort has been devoted to the formulation of predictive models of friction damper behavior in turbomachinery applications, especially for turbine blades, the problem is far from being solved due to the complex nonlinear behavior of the contact surfaces. This paper primarily focuses on analytical and numerical aspects of the problem and addresses the problem in the frequency domain while exploring the viability of equivalent time-domain alternatives. The distinct features of this work are: (i) the modelling of nonlinear friction damper behavior as an equivalent amplitude-dependent complex stiffness via a first-order harmonic balance method (HBM), (ii) the use of sine sweep excitation in time-marching analysis, (iii) the application of the methodology to numerical test cases, including an idealised 3D turbine blade model with several friction dampers, (iv) the verification of the numerical findings using experimental data, and (v) a detailed assessment of the suitability of HBM for the analysis of structures with friction dampers.

scholarly journals COMPARE THE EFFICIENCY OF CONTROLLED STIFFNESS DAMPER WITH VARIABLE FRICTION DAMPER FOR SEISMIC PROTECTION OF BUILDING

2009 ◽  
Vol 12 (8) ◽  
pp. 81-89
Author(s):  
Phuc Quang Bao Nguyen ◽  
Hoa Nhan Pham ◽  
Thang Quoc Chu
Keyword(s):  
Control Method ◽  
Seismic Protection ◽  
Control Law ◽  
Modal Control ◽  
Clamping Force ◽  
Friction Damper ◽  
Vibration Mitigation ◽  
Friction Dampers ◽  
Advantages And Disadvantages ◽  
Variable Friction

The implementation of variable friction dampers (VFD) for vibration mitigation of seismic structures generally requires an efficient semi-active control law. In this paper, a semi-active modal control method is proposed to determine the controllable clamping force of a variable friction damper. A comparative study was performed on a multiple DOF structure controlled by passive friction dampers, variable friction dampers in subsection numerical examples. Finally, this paper also provides preliminary conclusions about the advantages and disadvantages for friction dissipators.

An Overview of Several Formulations for Dry and Lubricated Revolute Joint Clearances in Planar Rigid-Multi-Body Mechanical Systems

2014 ◽  
Author(s):  
Paulo Flores ◽  
Hamid M. Lankarani
Keyword(s):  
Numerical Models ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Contact Forces ◽  
Hertzian Contact ◽  
Revolute Joint ◽  
Coulomb’S Friction ◽  
Revolute Joints ◽  
Joint Clearances ◽  
Multi Body

The influence of the revolute joint model on the dynamic response of planar multibody mechanical systems is studied in this work. In the sequel of this process, under the framework of the multibody formalisms, a general methodology for modeling the main kinematic aspects of dry revolute joint clearances is revisited. The numerical models for normal and tangential contact forces developed at the clearance joints are also discussed, which are based on the Hertzian contact theory and dry Coulomb’s friction law, respectively. The fundamental kinematic and dynamic issues of the modeling lubricated revolute joints are presented in this work in order to compare them with the dry revolute joint approach. In a simple manner, the lubrication forces are obtained by integrating the pressure distribution evaluated with the aid of Reynolds’ equation corresponding to the dynamic regime. The intra-joint forces developed for both dry and lubricated cases are evaluated based on the state of variable of the system and subsequently included into the dynamic equations of motion of the multibody system as external generalized forces. The main assumptions and procedures adopted throughout this work are demonstrated through simulations of a planar slider-crank mechanism, which includes dry and lubricated revolute joint with clearance. Finally, some experimental data is also presented and analyzed.

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