scholarly journals Vibration Characteristics of a Mistuned Bladed Disk considering the Effect of Coriolis Forces

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Xuanen Kan ◽  
Bo Zhao
Keyword(s):  
Coriolis Force ◽  
Rotational Speed ◽  
Natural Frequencies ◽  
Forced Response ◽  
Vibration Characteristics ◽  
Magnification Factor ◽  
Coriolis Forces ◽  
Rotating Speed ◽  
Bladed Disk ◽  
Coriolis Effects

To investigate the influence of Coriolis force on vibration characteristics of mistuned bladed disk, a bladed disk with 22 blades is employed and the effects of different rotational speeds and excitation engine orders on the maximum forced response are discussed considering the effects of Coriolis forces. The results show that if there are frequency veering regions, the largest split of double natural frequencies of each modal family considering the effects of Coriolis forces appears at frequency veering region. In addition, the amplitude magnification factor considering the Coriolis effects is increased by 1.02% compared to the system without considering the Coriolis effects as the rotating speed is 3000 rpm, while the amplitude magnification factor is increased by 2.76% as the rotating speed is 10000 rpm. The results indicate that the amplitude magnification factor may be moderately enhanced with the increasing of rotating speed. Moreover, the position of the maximum forced response of bladed disk may shift from one blade to another with the increasing of the rotational speed, when the effects of Coriolis forces are considered.

Coriolis Forces in Forced Response Analysis of Mistuned Bladed Discs

2006 ◽  
Author(s):  
M. Nikolic ◽  
E. P. Petrov ◽  
D. J. Ewins
Keyword(s):  
Primary Objective ◽  
Forced Response ◽  
Vibration Characteristics ◽  
Mutual Interaction ◽  
Response Analysis ◽  
Amplification Factors ◽  
Coriolis Forces ◽  
Coriolis Effects ◽  
Representative Model ◽  
Significant Factors

The problem of estimating the mutual interaction of the effects of Coriolis forces and of blade mistuning on the vibration characteristics of bladed discs is addressed in this paper. The influence of different degrees of mistuning on forced response and amplification factors are studied in the presence of Coriolis forces and then compared to their non-Coriolis counterparts using a computationally inexpensive, yet representative, model of a bladed disc. The primary objective of the study reported in this paper is to establish whether current mistuned bladed disc analyses should incorporate Coriolis effects in order to represent accurately all the significant factors that affect the forced response levels.

Investigation of Coriolis Effect on Vibration Characteristics of a Realistic Mistuned Bladed Disk

2011 ◽  
Author(s):  
Jianqiang Xin ◽  
Jianjun Wang
Keyword(s):  
Coriolis Force ◽  
Vibration Characteristics ◽  
Bladed Disks ◽  
Disk Model ◽  
Coriolis Forces ◽  
Response Characteristics ◽  
Bladed Disk ◽  
Damping Matrix ◽  
Disk Rotation ◽  
Speed Effect

Mistuning, which refers to inevitable variations in blades properties, will change the vibration of bladed disks dramatically. Bladed disks are exposed to effects of forces caused by bladed disk rotation, such as centrifugal and Coriolis forces. However, there is little research on the vibration behavior of a realistic bladed disk with Coriolis force. An investigation of the speed effect, i.e., the effects of centrifugal and Coriolis forces, on the vibration characteristics of a realistic mistuned bladed disk model is presented in this paper. Finite element method (FEM) is used to obtain the system mass, stiffness and damping matrix. The effects of Coriolis force and centrifugal force on the modal frequency and harmonic response characteristics of tuned bladed disk are investigated first, then the modal localization and response characteristics of mistuned bladed disk are researched. This investigation indicates that: Coriolis force has efficient influences on the modal and response characteristics of a realistic mistuned bladed disk: it can both increase and decrease the localization of the mistuned bladed disk for different situations.

Coriolis Forces in Forced Response Analysis of Mistuned Bladed Disks

2006 ◽  
Vol 129 (4) ◽  
pp. 730-739 ◽  
Author(s):  
M. Nikolic ◽  
E. P. Petrov ◽  
D. J. Ewins
Keyword(s):  
Primary Objective ◽  
Forced Response ◽  
Mutual Interaction ◽  
Response Analysis ◽  
Bladed Disks ◽  
Coriolis Forces ◽  
Bladed Disk ◽  
Coriolis Effects ◽  
Representative Model ◽  
Significant Factors

The problem of estimating the mutual interaction of the effects of Coriolis forces and of blade mistuning on the vibration characteristics of bladed disks is addressed in this paper. The influence of different degrees of mistuning on forced response and amplification factors are studied in the presence of Coriolis forces and then compared to their non-Coriolis counterparts using a computationally inexpensive, yet representative, model of a bladed disk. The primary objective of the study reported in this paper is to establish whether current mistuned bladed disk analyses should incorporate Coriolis effects in order to represent accurately all the significant factors that affect the forced response levels.

Vibration localization for a rotating mistuning bladed disk with the Coriolis effect by a state-space decoupling method

2017 ◽  
Vol 233 (3) ◽  
pp. 1011-1020 ◽  
Author(s):  
Xuanen Kan ◽  
Zili Xu
Keyword(s):  
State Space ◽  
Natural Frequency ◽  
Coriolis Force ◽  
High Speed ◽  
Forced Response ◽  
Coriolis Effect ◽  
Decoupling Method ◽  
Resonant Amplitude ◽  
Bladed Disk ◽  
Localization Factor

Slight deviations of blades due to manufacturing tolerances can cause mistuning of bladed disk leading to localized vibration, which can accelerate fatigue. Moreover, the rotating blades are subjected to the Coriolis effect and the influence of the Coriolis force on the natural frequencies of high-speed rotational bladed disks such as those of an aero-engine become more apparent. In this paper, the effect of Coriolis force on the forced response localization of a mistuned bladed disk are investigated, for conditions where the natural frequency located in the first and second modal families of the bladed disk. Mistuning is introduced by varying the Young’s modulus of each blade. Due to the asymmetric Coriolis matrix, it is not possible to directly decouple the system. A state-space decoupling method is developed to decouple the system to effectively calculate the forced response of bladed disk with the consideration of the Coriolis effect. The results show that response localization factor is increased by 13.09% considering the Coriolis force compared to the system without considering the Coriolis effect, in the case of where the first modal family is considered. In addition, the response localization factor with the consideration of the Coriolis force is decreased by 30.85% compared to the system without considering the Coriolis force, when the second modal family is considered. It indicates that the forced response localization with the consideration of the Coriolis effect will be changed obviously with the rotational speed increasing, when the concerning natural frequency is located in the first and second modal families. Furthermore, the effect of Coriolis force causes changes in the resonant frequencies and resonant amplitude, but does not introduce additional resonant peaks for the case of the mistuned bladed disk.

scholarly journals On Antiresonance in the Forced Response of Mistuned Bladed Disks

2003 ◽  
Vol 10 (2) ◽  
pp. 135-146 ◽  
Author(s):  
Keith Jones ◽  
Charles Cross
Keyword(s):  
Natural Frequencies ◽  
Critical Factor ◽  
Forced Response ◽  
Turbine Engines ◽  
Response Functions ◽  
Local Response ◽  
Bladed Disks ◽  
Important Conclusion ◽  
Bladed Disk ◽  
Lower Maximum

Mistuning in bladed disks usually increases the forced response of the maximum responding blade leading to shortened component life in turbine engines. This paper investigates mistuning using a transfer function approach where the frequency response functions (FRFs) are described by natural frequencies and antiresonant frequencies. Using this approach, antiresonant frequencies are shown to be a critical factor in determining the maximum blade response. Two insights are gained by formulating antiresonant frequencies as the eigenvalues of reduced system matrices: 1) Mistuning a particular blade has no effect on that blade's antiresonant frequencies. 2) Engine orders N and N/2, where N is the number of blades on the disk, tend to produce the highest maximum local response. Numerical examples are given using a spring-mass-oscillator model of a bladed disk. Pole-zero loci of mistuned bladed disks show that increased maximum blade response is often due to the damping of antiresonant frequencies. An important conclusion is that antiresonant frequencies can be arranged such that a mistuned bladed disk has a lower maximum blade response than a tuned bladed disk.

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.

Probabilistic Vibration Analysis of a Mistuned Integrally Bladed Disk

2014 ◽  
Vol 891-892 ◽  
pp. 726-731
Author(s):  
Guang Xia Chen ◽  
Jian Fu Hou
Keyword(s):  
Dynamic Characteristics ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Probabilistic Approach ◽  
Forced Response ◽  
Computational Time ◽  
Fe Model ◽  
Reduced Order ◽  
Bladed Disk ◽  
Model Size

Abstract. The objective of this paper is to probabilistically evaluate the effects of mistuned sectors on the dynamic characteristics of an integrally bladed disk (blisk). Small blade to blade physical variation in a disk is termed as mistuning. In this study, the dynamic characteristics of the perfectly tuned blisk were firstly analysed as a baseline. Secondly, a probabilistic approach is used for the mistuning analysis of a blisk. A reduced-order method named as the subset of nominal modes (SNM) was used to generate modes for a mistuned blisk from a cyclic perfectly tuned FE model without creating the full model. Furthermore, as only the modes with natural frequencies close to the modes of interest were considered, a relatively shorter computational time and a much smaller model size than a full blisk model is used. Therefore, the dynamic characteristics of the forced response for random mistuned blisks were obtained.

Mistuning Identification of Bladed Disks Utilizing Neural Networks

2010 ◽  
Author(s):  
M. Ersin Yu¨mer ◽  
Ender Cig˘erog˘lu ◽  
H. Nevzat O¨zgu¨ven
Keyword(s):  
Neural Networks ◽  
Mathematical Model ◽  
Case Studies ◽  
Natural Frequencies ◽  
Forced Response ◽  
Response Analysis ◽  
Bladed Disks ◽  
Data Set ◽  
Bladed Disk ◽  
New Methods

Mistuning affects forced response of bladed disks drastically; therefore, its identification plays an essential role in the forced response analysis of realistic bladed disk assemblies. Forced response analysis of mistuned bladed disk assemblies has drawn wide attention of researchers but there are a very limited number of studies dealing with identification of mistuning, especially if the component under consideration is a blisk (integrally bladed disk). This paper presents two new methods to identify mistuning of a rotor from the assembly modes via utilizing neural networks. It is assumed that a tuned mathematical model of the rotor under consideration is readily available, which is always the case for today’s realistic bladed disk assemblies. In the first method, a data set of selected mode shapes and natural frequencies is created by a number of simulations performed by mistuning the tuned mathematical model randomly. A neural network created by considering the number of modes, is then trained with this data set. Upon training the network, it is used to identify mistuning of the rotor from measured data. The second method further improves the first one by using it as starting point of an optimization routine and carries out an optimization to identify mistuning. To carry out identification analysis by means of the proposed methods, there are no limitations on the number of modes or natural frequencies to be used. Thus, they are suitable for incomplete data as well. Moreover, since system modes are used rather than blade alone counterparts, the techniques are ready to be used for analysis of blisks. Case studies are performed to demonstrate the capabilities of the new methods, using two different mathematical models to create training data sets; a lumped-parameter model and a relatively realistic reduced order model. Throughout the case studies, the effects of using incomplete mode families and random errors in assembly modes are investigated.

Systematic Mistuning of Bladed Disk Assemblies With Friction Contacts

2004 ◽  
Author(s):  
Florian Go¨tting ◽  
Walter Sextro ◽  
Lars Panning ◽  
Karl Popp
Keyword(s):  
Monte Carlo ◽  
Weibull Distribution ◽  
Approximate Method ◽  
Natural Frequencies ◽  
Forced Response ◽  
Mean Values ◽  
Friction Dampers ◽  
System Parameters ◽  
Bladed Disk ◽  
Standard Deviations

In turbomachinery, friction contacts are widely used to reduce dynamic stresses in turbine blades in order to avoid expensive damages. As a result of energy dissipation in the friction contacts the blade vibration amplitudes are reduced. In case of so-called friction dampers, which are pressed on the platforms of the blades by centrifugal forces, the damping effect can be optimized by varying the damper mass. This optimization can be done by means of a simulation model applying the so-called component mode synthesis and the Harmonic Balance Method to reduce computation time. It is based on the modal description of each substructure. In a real turbine or compressor blading great differences in the magnitude of the individual blade amplitudes occur caused by unavoidable mistuning of all system parameters like contact parameters and natural frequencies of the blades. It may happen that most of the blades experience only small stresses whereas a few blades experience critical stresses. Therefore, it is necessary to consider mistuning for all system parameters to simulate the forced response of bladed disk assemblies with friction contacts. For a mistuned bladed disk the complete system has to be modeled to calculate the dynamic response. In practice, usually the standard deviations instead of the distributions of the system parameters are known. Therefore, Monte-Carlo simulations are necessary to calculate the forced response of the blades for given mean values and standard deviations of the system parameters. To reduce the computational time, an approximate method has been developed and extended for small and moderate standard deviations of the system parameters to calculate the distribution and the envelopes of the frequency response functions for statistically varying system parameters, in the following called statistical mistuning. The approximate method is based on a sensitivity analysis and the assumption of a Weibull distribution of the vibration amplitudes of the blades. Both, the approximate method and the assumption of a Weibull distribution of the vibration amplitudes are validated by Monte-Carlo simulations. By these investigations the influence of different arrangements of the system parameters for given mean values and standard deviations of the vibration amplitudes of the blades can be determined, too. For the present investigations only a small influence of the arrangement of blades with respect to their natural frequencies has been observed. On the other hand, an intentional mistuning of the damper masses and the natural frequencies of the blades in a systematic way, in the following called systematic mistuning, can be investigated to reduce the amplitudes of the system. The simulation results of a systematic mistuning has been validated by a test rig with a rotating bladed disk assembly with friction dampers. The investigations show a good agreement between the simulations and the measurements but only a slight decrease of the maximum amplitudes in case of a systematic mistuning.

Mistuning Identification of Integrally Bladed Disks With Cascaded Optimization and Neural Networks

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Mehmet Ersin Yumer ◽  
Ender Cigeroglu ◽  
H. Nevzat Özgüven
Keyword(s):  
Neural Networks ◽  
Mathematical Model ◽  
Case Studies ◽  
Natural Frequencies ◽  
Forced Response ◽  
Response Analysis ◽  
Bladed Disks ◽  
Data Set ◽  
Bladed Disk ◽  
New Methods

Mistuning affects forced response of bladed disks drastically; therefore, its identification plays an essential role in the forced response analysis of bladed disk assemblies. Forced response analysis of mistuned bladed disk assemblies has drawn wide attention of researchers but there are a very limited number of studies dealing with identification of mistuning, especially if the component under consideration is an integrally bladed disk (blisk). This paper presents two new methods to identify mistuning of a bladed disk from the assembly modes via utilizing cascaded optimization and neural networks. It is assumed that a tuned mathematical model of the blisk under consideration is readily available, which is always the case for today’s realistic bladed disk assemblies. In the first method, a data set of selected mode shapes and natural frequencies is created by a number of simulations performed by mistuning the tuned mathematical model randomly. A neural network created by considering the number of modes, is then trained with this data set. Upon training the network, it is used to identify mistuning of the rotor from measured data. The second method further improves the first one by using it as a starting point of an optimization routine and carries out an optimization to identify mistuning. To carry out identification analysis by means of the proposed methods, there are no limitations on the number of modes or natural frequencies to be used. Thus, unlike existing mistuning identification methods they are suitable for incomplete data as well. Moreover, since system modes are used rather than blade alone counterparts, the techniques are ready to be used for analysis of blisks. Case studies are performed to demonstrate the capabilities of the new methods by using two different mathematical models to create training data sets a lumped-parameter model and a relatively realistic reduced order model. Throughout the case studies, the effects of using incomplete mode families and random errors in assembly modes are investigated. The results show that, the proposed method utilizing cascaded optimization and neural networks can identify mistuning parameters of a realistic blisk system with an exceptional accuracy even in the presence of incomplete and noisy test data.

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