Mistuning Analyses of a Bladed Disk: Pole-Zero and Modal Approaches

2008 ◽  
Author(s):  
Alok Sinha
Keyword(s):  
Natural Frequencies ◽  
Peak Amplitude ◽  
Mode Shapes ◽  
Bladed Disk ◽  
Amplitude Maximum ◽  
Excitation Frequencies ◽  
Amplitude Amplification

This paper examines the fundamental aspects of amplitude amplification due to mistuning in a bladed disk. Both pole-zero and modal approaches are used to understand the effects of changes in mode shapes and the natural frequencies on the minimum and maximum values of peak amplitudes among all blades over all excitation frequencies. The nature of variation of this peak amplitude is studied, and algorithms are discussed to determine the statistics of the peak amplitude, maximum and minimum values of the peak amplitude, and corresponding mistuning patterns.

scholarly journals High-Fidelity Sensitivity Analysis of Modal Properties of Mistuned Bladed Disks Regarding Material Anisotropy

2018 ◽  
Author(s):  
Adam Koscso ◽  
Guido Dhondt ◽  
E. P. Petrov
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Coordinate Systems ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Material Orientation

A new method has been developed for sensitivity calculations of modal characteristics of bladed disks made of anisotropic materials. The method allows the determination of the sensitivity of the natural frequencies and mode shapes of mistuned bladed disks with respect to anisotropy angles that define the crystal orientation of the monocrystalline blades using full-scale finite element models. An enhanced method is proposed to provide high accuracy for the sensitivity analysis of mode shapes. An approach has also been developed for transforming the modal sensitivities to coordinate systems used in industry for description of the blade anisotropy orientations. The capabilities of the developed methods are demonstrated on examples of a single blade and a mistuned realistic bladed disk finite element models. The modal sensitivity of mistuned bladed disks to anisotropic material orientation is thoroughly studied.

Flutter and Forced Vibration Characteristics of a Turbo Fan Bladed Disk Rotor

2013 ◽  
Author(s):  
Madhavan Srinivasan ◽  
Sankarkumar Jeyaraman ◽  
Rajeev Jain ◽  
Sujatha Chandramohan ◽  
Sekhar AnandaRao Seshadri
Keyword(s):  
Forced Vibration ◽  
Natural Frequencies ◽  
Fluid Dynamic ◽  
Mode Shapes ◽  
Blade Vibration ◽  
Engine Operation ◽  
Bladed Disk ◽  
Blade Flutter ◽  
Loss Of Thrust

Aero-elastic excitation can result in excessive blade vibration, which can cause blades to fail in high cycle fatigue (HCF). A severe aero-elastic failure can result in a complete blade separation and loss of thrust and loss of a blade can mean the loss of an aircraft. The primary aeromechanical design concerns are blade flutter and forced vibration that need to be quantified at the early part of engine tests. This paper details the experimental investigation carried out on a transonic shroudless low aspect ratio fan bladed disk that experienced subsonic/transonic stall flutter and forced vibration excitation. Experiments are performed on a full scale engine using tip timing sensors flush mounted on the fan casing to characterize the vibratory responses during flutter and forced vibration conditions during engine operation. Numerical simulations are performed using computational fluid dynamic (CFD) analysis. Blade natural frequencies and mode shapes are obtained from finite element (FE) modal analysis. The experimental data captured from engine tests are used to validate the predicted results.

Multistage Coupling of Eight Mistuned Bladed Disk on a Solid Shaft: Part 1—Free Vibration Analysis

2012 ◽  
Author(s):  
Romuald Rzadkowski ◽  
Artur Maurin
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Free Vibration Analysis ◽  
Free Vibrations ◽  
Rotor Blades ◽  
Mode Shapes ◽  
Bladed Disk ◽  
Centrifugal Stiffening

Considered here was the effect of multistage coupling on the dynamics of a rotor consisting of eight mistuned bladed discs on a solid shaft. Each bladed disc had a different number of rotor blades. Free vibrations were examined using finite element representations of rotating single blades, bladed discs, and the entire rotor. In this study the global rotating mode shapes of eight flexible mistuned bladed discs on shaft assemblies were calculated, taking into account rotational effects such as centrifugal stiffening. The thus obtained natural frequencies of the blade, shaft, bladed disc and entire shaft with discs were carefully examined to discover resonance conditions and coupling effects. This study found that mistuned systems cause far more intensive multistage coupling than tuned ones. The greater the mistuning, the more intense the multistage coupling.

scholarly journals High-Fidelity Sensitivity Analysis of Modal Properties of Mistuned Bladed Disks Regarding Material Anisotropy

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Adam Koscso ◽  
Guido Dhondt ◽  
E. P. Petrov
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Coordinate Systems ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Material Orientation

A new method has been developed for sensitivity calculations of modal characteristics of bladed disks made of anisotropic materials. The method allows the determination of the sensitivity of the natural frequencies and mode shapes of mistuned bladed disks with respect to anisotropy angles that define the crystal orientation of the monocrystalline blades using full-scale finite element models. An enhanced method is proposed to provide high accuracy for the sensitivity analysis of mode shapes. An approach has also been developed for transforming the modal sensitivities to coordinate systems (CS) used in industry for description of the blade anisotropy orientations. The capabilities of the developed methods are demonstrated on examples of a single blade and a mistuned realistic bladed disk finite element models. The modal sensitivity of mistuned bladed disks to anisotropic material orientation is thoroughly studied.

Optimal Stiffness Parameters of the Turbine Bladed Disk Computational Model

2013 ◽  
Author(s):  
Pavel Polach
Keyword(s):  
Computational Model ◽  
Steam Turbine ◽  
Topical Application ◽  
Natural Vibration ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Centrifugal Forces ◽  
Bladed Disk ◽  
Real Contact ◽  
Optimal Stiffness

Motivation for introducing this paper is the topical application of the method using the rotational periodicity of the structure at calculating natural vibration characteristics of the steam turbine bladed disk with continuous binding, in this case in the form of integral shrouding and in the middle of the blade with the tie-boss connection. Part of the shroud and the part of the tie-boss are the integral parts of the blade. Blades are free at non-rotating bladed disk. Blades of the advanced design are continuously coupled in the zone of the shroud and in the tie-boss zone by the blades untwist caused by the centrifugal forces acting at turbine rotation. The method used for the calculation of natural frequencies and mode shapes of the bladed disk with the continuous binding does not enable to model the real contact properties. The contact must be modeled by the flexible connection. The stiffness of the connection in the zones of adjoining blades contact is “tuned” at turbine operational speed (i.e. at 3000 rpm) in such a way that the values of calculated natural frequencies may come as near as possible to the values of the measured natural frequencies.

An Investigation of Dual Mode Phenomena in a Mistuned Bladed Disk

1983 ◽  
Vol 105 (3) ◽  
pp. 402-407 ◽  
Author(s):  
W. A. Stange ◽  
J. C. MacBain
Keyword(s):  
Strain Gage ◽  
Holographic Interferometry ◽  
Rotational Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Dual Mode ◽  
Disk Model ◽  
Bladed Disk ◽  
Mode Splitting ◽  
Modes Of Vibration

This paper presents the results of an investigation addressing the effects of mistuning on the lower modes of vibration of a simple bladed-disk model. The phenomena of dual modes, also known as mode splitting, is studied using holographic interferometry and strain gage measurements under nonrotating and rotating conditions. Resonant amplitudes, mode shapes, and natural frequencies of the disk model were determined, without deliberately mistuning the disk. The tests were then repeated with the disk deliberately mistuned to varying degrees, paying particular attention to the second diameter (2N) dual modes. Additionally, tests were conducted on the disk at a rotational speed of 2000 rpm, in an effort to gain insight as to the vibratory characteristics of the disk under rotating conditions.

Reliability Evaluation of Shrouded Blading Using the SAFE Interference Diagram

1989 ◽  
Vol 111 (4) ◽  
pp. 601-609 ◽  
Author(s):  
M. P. Singh ◽  
J. J. Vargo
Keyword(s):  
Natural Frequencies ◽  
Reliability Evaluation ◽  
Mode Shapes ◽  
Design Evaluation ◽  
Campbell Diagram ◽  
Bladed Disk ◽  
Design Reliability

The SAFE Interference Diagram is shown to be useful in the design reliability evaluation of shrouded blading, including long-arc shrouding construction. This method provides an alternate method to the widely used Campbell diagram and also brings in more information for easier design evaluation. The SAFE diagram uses the natural frequencies of an entire bladed disk rather than individual blade or packet frequencies. In addition, it compares frequencies, mode shapes, and speed to evaluate whether a resonance occurs. Theoretical arguments are provided for the validity of the SAFE Diagram and its usefulness is shown by practical examples. This method provides an easier means to show why long-arc shrouding works and also when it might not.

High Fidelity Transient Forced Response Analysis of Mistuned Bladed Disks Under Complex Excitation and Variable Rotation Speeds

2020 ◽  
Author(s):  
Jing Tong ◽  
Chaoping Zang ◽  
Evgeny Petrov
Keyword(s):  
Large Scale ◽  
Rotation Speed ◽  
Dynamic Properties ◽  
Spectral Composition ◽  
Forced Response ◽  
Mode Shapes ◽  
Response Analysis ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Amplitude Amplification

Abstract An effective method is developed for the efficient calculation of the transient vibration response for mistuned bladed disks under complex excitation and varying rotation speeds. The method uses the large-scale finite element modelling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks. The realistic distributions of the excitation forces are considered, which resulted in the multiharmonic excitation loads. The transient response calculation is based on the analytically derived expressions for the transient forced response and the effective method used for the model reduction. The effects of the varying rotation speed on the natural frequencies and mode shapes of the mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are allowed for. The different functions of the rotation speed variation can be analyzed. Numerical studies of the transient forced response and the amplitude amplification in mistuned bladed disks are performed when the resonance regimes are passed during gas-turbine engine acceleration or deceleration. The effects of different types of excitation force and mistuning on transient amplitude amplification are illustrated by a large number of the computational results and comparative analysis. These results and analysis of transient forced response are shown on an example of a realistic mistuned bladed disk.

Experiments and Calculations on the Vibrations of Rotating Radial Impellers

1988 ◽  
Vol 110 (2) ◽  
pp. 137-142 ◽  
Author(s):  
Horst Irretier
Keyword(s):  
Rotational Speed ◽  
Natural Frequencies ◽  
Numerical Results ◽  
Mode Shapes ◽  
Resonance Excitation ◽  
Rotating Waves ◽  
Excitation Frequencies ◽  
Run Up

Experimental and numerical results on the vibrations of a rotating radial impeller are presented. They show natural frequencies as a function of rotational speed, the mode shapes, the resonance excitation frequencies of the forward and backward rotating waves, and a response diagram during a run-up of the impeller.

scholarly journals High Vibration Problem in Compressor Piping Systems: A Case Study

1997 ◽  
Author(s):  
G. Vijaya Kumar ◽  
S. Raghava Chary ◽  
A. Rajamani
Keyword(s):  
Natural Frequencies ◽  
Excitation Frequency ◽  
Mode Shapes ◽  
Piping System ◽  
Mechanical Responses ◽  
Normal Limits ◽  
Piping Systems ◽  
Vibration Problems ◽  
Excitation Frequencies

High vibration problems resulting in damage to supports, instrument stubs etc. have been experienced in many compressor piping systems installed at different fertilizer plants. Investigations aimed at a solution to the problem included vibration measurements on the suction and discharge piping, and mathematical modeling of the piping. The measurements indicated presence of an excitation frequency in the range of 30–35% of the compressor running speed. Dynamic analysis of the piping system showed the presence of natural frequencies coinciding with or very near to the excitation frequencies. This has been further confirmed by impact tests. Analytical mode shapes clearly show that the antinodes match with high vibration zones observed at the site. The mathematical models were used to determine optimum configurations which would separate mechanical responses from excitation frequencies. These modifications have been implemented at site and the piping vibrations are within normal limits.

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