scholarly journals Validation of a Modal Work Approach for Forced Response Analysis of Bladed Disks

2021 ◽  
Vol 11 (12) ◽  
pp. 5437
Author(s):  
Lorenzo Pinelli ◽  
Francesco Lori ◽  
Michele Marconcini ◽  
Roberto Pacciani ◽  
Andrea Arnone
Keyword(s):  
Forced Response ◽  
Response Analysis ◽  
Test Case ◽  
Cyclic Symmetry ◽  
Bladed Disks ◽  
Low Pressure Turbine ◽  
Bladed Disk ◽  
Forcing Function ◽  
Bladed Rotor ◽  
Good Agreement

The paper describes a numerical method based on a modal work approach to evaluate the forced response of bladed disks and its validation against numerical results obtained by a commercial FEM code. Forcing functions caused by rotor–stator interactions are extracted from CFD unsteady solutions properly decomposed in time and space to separate the spinning perturbation acting on the bladed disk in a cyclic environment. The method was firstly applied on a dummy test case with cyclic symmetry where the forcing function distributions were arbitrarily selected: comparisons for resonance and out of resonance conditions revealed an excellent agreement between the two numerical methods. Finally, the validation was extended to a more realistic test case representative of a low-pressure turbine bladed rotor subjected to the wakes of two upstream rows: an IGV with low blade count and a stator row. The results show a good agreement and suggest computing the forced response problem on the finer CFD blade surface grid to achieve a better accuracy. The successful validation of the method, closely linked to the CFD environment, creates the opportunity to include the tool in an integrated multi-objective procedure able to account for aeromechanical aspects.

Impact of Turbine Center Frame Wakes on Downstream Rows in Heavy-Duty Low-Pressure Turbine

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Sara Biagiotti ◽  
Juri Bellucci ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Gino Baldi ◽  
...  
Keyword(s):  
Experimental Data ◽  
Low Pressure ◽  
Numerical Approach ◽  
Forced Response ◽  
Operating Conditions ◽  
Response Analysis ◽  
Test Case ◽  
Low Pressure Turbine ◽  
Harmonic Content ◽  
The Impact

Abstract In this work, the effects of turbine center frame (TCF) wakes on the aeromechanical behavior of the downstream low-pressure turbine (LPT) blades are numerically investigated and compared with the experimental data. A small industrial gas turbine has been selected as a test case, composed of a TCF followed by the two low-pressure stages and a turbine rear frame (TRF) before the exhaust plenum. Full annulus unsteady computations of the whole low-pressure module have been performed. Two operating conditions, full (100%) and partial (50%) load, have been investigated with the aim of highlighting the impact of TCF wakes convection and diffusion through the downstream rows. Attention was paid to the harmonic content of rotors’ blades. The results show a slower decay of the wakes through the downstream rows in off-design conditions compared with the design point. The analysis of the rotors’ frequency spectrum reveals that moving from design to off-design conditions, the effect of the TCF does not change significantly. The harmonic contribution of all turbine components has been extracted, highlighting the effect of statoric parts on the last LPT blade. The TCF harmonic content remains the most relevant from an aeromechanic point of view as per experimental evidence, and it is considered for an forced response analysis (FRA) on the last LPT blade itself. Finally, aerodynamic and aeromechanic predictions have been compared with the experimental data to validate the numerical approach. Some general design solutions aimed at mitigating the TCF wakes impact are discussed.

Resonant Response of Mistuned Bladed Disk Expressed by Vibratory Stress

2016 ◽  
Author(s):  
Yasutomo Kaneko ◽  
Kazushi Mori ◽  
Hiroharu Ooyama
Keyword(s):  
Stress Response ◽  
Amplification Factor ◽  
Forced Response ◽  
Response Analysis ◽  
Flat Plates ◽  
Bladed Disks ◽  
Displacement Response ◽  
Bladed Disk ◽  
Excited Vibration ◽  
Blade Flutter

Although bladed disks of turbomachinery are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all blades on a disk are slightly different due to the manufacturing tolerance, the deviation of the material property, the wear during operation, and so on. These small variations break the cyclic symmetry, and split the eigenvalue pairs. The actual bladed disks with the small variations are referred to a mistuned system. In the forced response of a mistuned bladed disk, the responses of all blades become different, and the response of a certain blade may become extremely large due to the split of the duplicated eigenvalues, the distortion of the vibration modes, and so on. On the other hand, many researchers suggest that the mistuning suppresses the blade flutter, because the complete travelling wave mode is not formed in a disk. In other words, the main conclusions of researches on mistuning are that while mistuning has an undesirable effect on the forced response, it has a beneficial (stabilizing) effect on the blade flutter (the self-excited vibration). Although such mistuning phenomena of bladed disks have been studied since 1980s, almost all studies focused on the amplification factor of the displacement response, and few studies researched the amplification factor of the vibratory stress response. In this study, first, the frequency response analysis of the mistuned simple bladed disk consisting of flat plates is carried out. Comparing the amplification factor of the displacement response with that of the vibratory stress response, the amplification factor expressed by the vibratory stress is studied in detail. Second, the mistuning analysis of the actual bladed disk used in a steam turbine is carried out. From these results, the mistuning effect expressed by the vibratory stress is clarified.

Analysis of Forced Response for Bladed Disks Mistuned by Material Anisotropy Orientation Scatters

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Chaoping Zang ◽  
Yuanqiu Tan ◽  
E. P. Petrov
Keyword(s):  
Finite Element ◽  
Monte Carlo ◽  
High Accuracy ◽  
Forced Response ◽  
Response Analysis ◽  
High Fidelity ◽  
Fe Model ◽  
Material Anisotropy ◽  
Bladed Disks ◽  
Bladed Disk

A new method is developed for the forced response analysis of mistuned bladed disks manufactured from anisotropic materials and mistuned by different orientations of material anisotropy axes. The method uses (i) sector finite element (FE) models of anisotropic bladed disks and (ii) FE models of single blades and allows the calculation of displacements and stresses in a mistuned assembly. A high-fidelity reduction approach is proposed which ensures high-accuracy modeling by introducing an enhanced reduction basis. The reduction basis includes the modal properties of specially selected blades and bladed disks. The technique for the choice of the reduction basis has been developed, which provides the required accuracy while keeping the computation expense acceptable. An approach for effective modeling of anisotropy-mistuned bladed disk without a need to create a FE model for each mistuning pattern is developed. The approach is aimed at fast statistical analysis based on Monte Carlo simulations. All components of the methodology for anisotropy-mistuned bladed disks are demonstrated on the analysis of models of practical bladed disks. Effects of anisotropy mistuning on forced response levels are explored.

scholarly journals Sensitivity and Forced Response Analysis of Anisotropy-Mistuned Bladed Disks With Nonlinear Contact Interfaces

2019 ◽  
Author(s):  
Adam Koscso ◽  
E. P. Petrov
Keyword(s):  
Harmonic Balance Method ◽  
Computational Effort ◽  
Forced Response ◽  
Response Analysis ◽  
Nonlinear Friction ◽  
Material Anisotropy ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Nonlinear Contact ◽  
Blade Model

Abstract A new method has been developed for the analysis of nonlinear forced response of bladed disks mistuned by blade anisotropy scatter and for the forced response sensitivity to blade material anisotropy orientations. The approach allows for the calculation of bladed disks with nonlinear friction contact interfaces using the multi-harmonic balance method. The method uses efficient high-accuracy model reduction method for the minimization of the computational effort while providing required accuracy. The capabilities of the developed methods are validated and demonstrated using a two-blade model. A thorough study of the influence of the material anisotropy mistuning and its sensitivity on the characteristics of the forced response is carried out using finite element modes of anisotropy mistuned realistic bladed disk with nonlinear friction joints of blade roots and shroud contacts. The dependency of the nonlinear forced response on excitation level and contact pressure values has been carried out for anisotropy mistuned bladed disks.

A Method for Forced Response Analysis of Mistuned Bladed Disks With Aerodynamic Effects Included

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Flow ◽  
Forced Response ◽  
Response Analysis ◽  
Bladed Disks ◽  
Blade Vibration ◽  
Disk Model ◽  
Mechanical Coupling ◽  
Bladed Disk ◽  
Flexible Disk ◽  
Function Matrix

A method has been developed for high-accuracy analysis of forced response levels for mistuned bladed disks vibrating in gas flow. Aerodynamic damping, the interaction of vibrating blades through gas flow, and the effects of structural and aerodynamic mistuning are included in the bladed disk model. The method is applicable to cases of high mechanical coupling of blade vibration through a flexible disk and, possibly shrouds, to cases with stiff disks and low mechanical coupling. The interaction of different families of bladed disk modes is included in the analysis providing the capability of analyzing bladed disks with pronounced frequency veering effects. The method allows the use of industrial-size sector models of bladed disks for analysis of forced response of a mistuned structure. The frequency response function matrix of a structurally mistuned bladed disk is derived with aerodynamic forces included. A new phenomenon of reducing bladed disk forced response by mistuning to levels that are several times lower than those of their tuned counterparts is revealed and explained.

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.

scholarly journals Sensitivity and Forced Response Analysis of Anisotropy-Mistuned Bladed Disks With Nonlinear Contact Interfaces

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Adam Koscso ◽  
Evgeny Petrov
Keyword(s):  
Reduction Method ◽  
Computational Effort ◽  
Forced Response ◽  
Response Analysis ◽  
Nonlinear Friction ◽  
Material Anisotropy ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Nonlinear Contact ◽  
Blade Model

AbstractA new method has been developed for the analysis of nonlinear forced response of bladed disks mistuned by blade anisotropy scatter and for the forced response sensitivity to blade material anisotropy orientations. The approach allows for the calculation of bladed disks with nonlinear friction contact interfaces using the multiharmonic balance method. The method uses efficient high-accuracy model reduction method for the minimization of the computational effort while providing required accuracy. The capabilities of the developed methods are validated and demonstrated using a two-blade model. A thorough study of the influence of the material anisotropy mistuning and its sensitivity on the characteristics of the forced response is carried out using finite element (FE) modes of anisotropy mistuned realistic bladed disk with nonlinear friction joints of blade roots and shroud contacts. The dependency of the nonlinear forced response on excitation level and contact pressure values has been carried out for anisotropy mistuned bladed disks.

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.

Effects of Damping and Varying Contact Area at Blade-Disk Joints in Forced Response Analysis of Bladed Disk Assemblies

2005 ◽  
Vol 128 (2) ◽  
pp. 403-410 ◽  
Author(s):  
E. P. Petrov ◽  
D. J. Ewins
Keyword(s):  
Large Scale ◽  
Normal Load ◽  
Forced Response ◽  
Response Analysis ◽  
Finite Element Models ◽  
Bladed Disks ◽  
Contact Conditions ◽  
New Approach ◽  
Bladed Disk ◽  
Unilateral Contacts

An approach is developed to analyze the multiharmonic forced response of large-scale finite element models of bladed disks taking account of the nonlinear forces acting at the contact interfaces of blade roots. Area contact interaction is modeled by area friction contact elements which allow for friction stresses under variable normal load, unilateral contacts, clearances, and interferences. Examples of application of the new approach to the analysis of root damping and forced response levels are given and numerical investigations of effects of contact conditions at root joints and excitation levels are explored for practical bladed disks.

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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