A Subspace Method for Modal Identification of Bladed Assemblies Using Blade Tip-Timing Data

2007 ◽  
Author(s):  
Bendali Salhi ◽  
Marc Berthillier ◽  
Joseph Lardies ◽  
Philippe Voinis ◽  
Charles Bodel
Keyword(s):  
Natural Frequencies ◽  
Standard Procedure ◽  
Modal Identification ◽  
Subspace Method ◽  
Subspace Analysis ◽  
Bladed Disk ◽  
Fast Fourier Transform Analysis ◽  
Timing Data ◽  
Vibration Responses ◽  
Blade Tip

Unknown excitation forces are applied to bladed disk assemblies, such as turbines blades, leading to forced vibration responses. Non contact measurement of such vibrations using blade tip-timing data has become an industrial standard procedure and current research focuses on analysis methods for interpretation of measured vibrations. Our purpose is to develop a method for identification of the blade’s natural frequencies and damping ratios using blade tip-timing data. The method is based on a subspace analysis. Its performance is compared to the traditional Fast Fourier Transform analysis. A detailed description of these methods and results are presented.

Simulation of Tip-Timing Measurements of a Cracked Bladed Disk Forced Response

2010 ◽  
Author(s):  
Vsevolod Kharyton ◽  
Jean-Pierre Laine ◽  
Fabrice Thouverez ◽  
Olexiy Kucher
Keyword(s):  
Dynamic Model ◽  
Harmonic Balance Method ◽  
Time History ◽  
Forced Response ◽  
Bladed Disk ◽  
Crack Behavior ◽  
Timing Data ◽  
History Of ◽  
Blade Tip ◽  
Blade Frequency

The study intends to simulate the process of the blade tip amplitude calculation by the tip-timing method. An attention is focused on tip-timing measurements for detection of a cracked blade from the bladed disk forced response. The cracked blade is considered within frameworks of the bladed disk dynamic model that takes into account mistuning presence. Nonlinear formulation of a crack behavior is done with the harmonic balance method in its combination with the contact analysis that allows simulation of crack breathing. In order to make the cracked blade detection process evident, the crack length and location are set in such a way as to produce the cracked blade frequency localization. Reconstruction of the blade tip amplitudes is attained with the arriving time of measured probes of the blade tips. The results are compared with the blade forced response obtained by the bladed disk dynamic model. A possibility is also considered how to reconstruct time-history of the bladed disk forced response with tip-timing data.

scholarly journals Determination of Simultaneous Steady-State Movements Using Blade Tip Timing Data

2019 ◽  
Author(s):  
Mohamed Mohamed ◽  
Philip Bonello ◽  
Peter Russhard
Keyword(s):  
Previous Method ◽  
Vibration Measurement ◽  
Single Type ◽  
Bladed Disk ◽  
Shaft System ◽  
Axial Movement ◽  
Timing Data ◽  
Blade Tip ◽  
Uncertainty Level

Abstract Blade tip timing (BTT) includes a number of uncertainties that discourage its use. One of the main ones is the shift in the equilibrium position of the blade tip due to steady (non-oscillatory) bending and/or twisting of the blade, and axial movement of the bladed disk (blisk)-shaft system. This results in a shift in the effective measurement position of the probe relative to the blade chord, resulting in errors in the tip vibration measurement which can translate to a huge error in the corresponding stress estimate, which relies on calibration against finite element (FE) models. Previous experimentally validated research by the authors introduced a method for quantifying steady movement of a single type (axial, lean, or untwist), using BTT data from not more than two probes. In this paper, a development of the previous method is presented that provides a solution for the case of simultaneous types of blade steady movements. Additional probes are used for determining the direction, but these can be placed at any angular positions. The developed method is validated using a BTT simulator of a blisk, and accurate results obtained. The simultaneous axial and lean movements can be accurately determined when the untwist is negligible, and an uncertainty level can be specified when the untwist is not negligible. The untwist itself can be calculated accurately in all cases of simultaneous movements. Guidelines for the use of the method in different scenarios are provided.

scholarly journals Active Vibration-Based Condition Monitoring of a Transmission Line

Actuators ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 309
Author(s):  
Liuhuo Wang ◽  
Chengfeng Liu ◽  
Xiaowei Zhu ◽  
Zhixian Xu ◽  
Wenwei Zhu ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Engineering Application ◽  
Vibration Response ◽  
Modal Identification ◽  
Wireless Sensor ◽  
Transmission Tower ◽  
Transmission Towers ◽  
Vibration Responses ◽  
Active Vibration ◽  
Settlement Experiment

In the power system, the transmission tower is located in a variety of terrains. Sometimes there will be displacement, inclination, settlement and other phenomena, which eventually lead to the collapse of the tower. In this paper, a method for monitoring the settlement of a transmission tower based on active vibration response is proposed, which is based on the principle of modal identification. Firstly, a device was designed, which includes three parts: a monitoring host, wireless sensor and excitation device. It can tap the transmission tower independently and regularly, and collect the vibration response of the transmission tower. Then, vibration analysis experiments were used to validate the horizontal vibration responses of transmission towers which can be obtained by striking the transmission towers from either the X direction or Y direction. It can be seen from the frequency response function that the natural frequencies obtained from these two directions are identical. Finally, the transmission tower settlement experiment was carried out. The experimental results show that the third to fifth natural frequencies decreased most obviously, even up to 2.83 Hz. Further, it was found that under different conditions, as long as the tower legs adjacent to the excitation position settle, the natural frequency will decrease more significantly, which is very helpful for engineering application.

scholarly journals Determination of Simultaneous Steady-State Movements Using Blade Tip Timing Data

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Mohamed Elsayed Mohamed ◽  
Philip Bonello ◽  
Peter Russhard
Keyword(s):  
Previous Method ◽  
Vibration Measurement ◽  
Single Type ◽  
Bladed Disk ◽  
Shaft System ◽  
Axial Movement ◽  
Timing Data ◽  
Blade Tip ◽  
Uncertainty Level

Abstract Blade tip timing (BTT) includes a number of uncertainties that discourage its use. One of the main ones is the shift in the equilibrium position of the blade tip due to steady (non-oscillatory) bending and/or twisting of the blade, and axial movement of the bladed disk (blisk)-shaft system. This results in a shift in the effective measurement position of the probe relative to the blade chord, resulting in errors in the tip vibration measurement which can translate to a huge error in the corresponding stress estimate, which relies on calibration against finite element (FE) models. Previous experimentally validated research by the authors introduced a method for quantifying steady movement of a single type (axial, lean, or untwist), using BTT data from not more than two probes. In this paper, a development of the previous method is presented that provides a solution for the case of simultaneous types of blade steady movements. Additional probes are used for determining the direction, but these can be placed at any angular positions. The developed method is validated using a BTT simulator of a blisk, and accurate results obtained. The simultaneous axial and lean movements can be accurately determined when the untwist is negligible, and an uncertainty level can be specified when the untwist is not negligible. The untwist itself can be calculated accurately in all cases of simultaneous movements. Guidelines for the use of the method in different scenarios are provided.

Vacuum Spin Test Series of a Turbine Impeller With Focus on Mistuning and Damping by Comparing Tip Timing and Strain Gauge Results

2015 ◽  
Author(s):  
Thomas Maywald ◽  
Bernd Beirow ◽  
Christoph R. Heinrich ◽  
Arnold Kühhorn
Keyword(s):  
Strain Gauge ◽  
Natural Frequencies ◽  
Forced Response ◽  
Test Series ◽  
Strain Gauges ◽  
Special Focus ◽  
Bladed Disk ◽  
Blade Tip ◽  
Effects Of Rotation ◽  
Turbine Impeller

This paper describes preparation, execution and evaluation of a comprehensive bladed disk spin test series. At the example of an turbine impeller the effects of rotation and temperature are analyzed with special focus on mistuning and damping. The forced response is measured synchronously via 13 identical positioned strain gauges on each blade as well as via blade tip-timing. Subsequently it is possible to compare the results of both systems. During the test series rotational speed varies in the range from 10.000 up to 19.000 RPM. Simultaneously, the wheel is heated up to 820 K by an oven. A number of pre-selected natural frequencies, damping ratios and operating deflection shapes are evaluated and compared with respect to different rotational speeds and impeller temperatures.

scholarly journals Spatially Resolved Experimental Modal Analysis on High-Speed Composite Rotors Using a Non-Contact, Non-Rotating Sensor

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4705
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Juergen Czarske ◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Fiber Reinforced ◽  
Structural Dynamic ◽  
Spatially Resolved ◽  
Glass Fiber Reinforced ◽  
Vibration Responses ◽  
And Performance

Due to their lightweight properties, fiber-reinforced composites are well suited for large and fast rotating structures, such as fan blades in turbomachines. To investigate rotor safety and performance, in situ measurements of the structural dynamic behaviour must be performed during rotating conditions. An approach to measuring spatially resolved vibration responses of a rotating structure with a non-contact, non-rotating sensor is investigated here. The resulting spectra can be assigned to specific locations on the structure and have similar properties to the spectra measured with co-rotating sensors, such as strain gauges. The sampling frequency is increased by performing consecutive measurements with a constant excitation function and varying time delays. The method allows for a paradigm shift to unambiguous identification of natural frequencies and mode shapes with arbitrary rotor shapes and excitation functions without the need for co-rotating sensors. Deflection measurements on a glass fiber-reinforced polymer disk were performed with a diffraction grating-based sensor system at 40 measurement points with an uncertainty below 15 μrad and a commercial triangulation sensor at 200 measurement points at surface speeds up to 300 m/s. A rotation-induced increase of two natural frequencies was measured, and their mode shapes were derived at the corresponding rotational speeds. A strain gauge was used for validation.

Sparse Reconstruction Method of Non-Uniform Sampling and its Application in Blade Tip Timing System

2020 ◽  
Author(s):  
Jie Tian ◽  
Xiaopu Zhang ◽  
Yong Chen ◽  
Peter Russhard ◽  
Hua Ouyang
Keyword(s):  
Compressive Sensing ◽  
Sparse Reconstruction ◽  
Reconstruction Method ◽  
Blade Vibration ◽  
Uniform Sampling ◽  
Blade Vibrations ◽  
Timing Data ◽  
Blade Tip ◽  
Simultaneous Identification ◽  
Multi Mode

Abstract Based on the blade vibration theory of turbomachinery and the basic principle of blade timing systems, a sparse reconstruction model is derived for the tip timing signal under an arbitrary sensor circumferential placement distribution. The proposed approach uses the sparsity of the tip timing signal in the frequency domain. The application of compressive sensing in reconstructing the blade tip timing signal and monitoring multi-mode blade vibrations is explored. To improve the reconstruction effect, a number of numerical experiments are conducted to examine the effects of various factors on synchronous and non-synchronous signals. This enables the specific steps involved in the compressive sensing reconstruction of tip timing signals to be determined. The proposed method is then applied to the tip timing data of a 27-blade rotor. The results show that the method accurately identifies the multi-mode blade vibrations at different rotation speeds. The proposed method has the advantages of low dependence on prior information, insensitivity to environmental noise, and simultaneous identification of synchronous and non-synchronous signals. The experimental results validate the effectiveness of the proposed approach in engineering applications.

scholarly journals A Class of Methods for the Analysis of Blade Tip Timing Data from Bladed Assemblies Undergoing Simultaneous Resonances—Part II: Experimental Validation

2007 ◽  
Vol 2007 ◽  
pp. 1-10 ◽  
Author(s):  
J. Gallego-Garrido ◽  
G. Dimitriadis ◽  
I. B. Carrington ◽  
J. R. Wright
Keyword(s):  
Experimental Test ◽  
Experimental Validation ◽  
Test Rig ◽  
New Techniques ◽  
Analysis Techniques ◽  
Simultaneous Resonances ◽  
Timing Data ◽  
Blade Tip ◽  
Using Data ◽  
Double Resonances

Blade tip timing is a technique for the measurement of vibrations in rotating bladed assemblies. In Part I of this work a class of methods for the analysis of blade tip timing data from bladed assemblies undergoing two simultaneous synchronous resonances was developed. The approaches were demonstrated using data from a mathematical simulation of tip timing data. In Part II the methods are validated on an experimental test rig. First, the construction and characteristics of the rig will be discussed. Then, the performance of the analysis techniques when applied to data from the rig will be compared and analysed. It is shown that accurate frequency estimates are obtained by all the methods for both single and double resonances. Furthermore, the recovered frequencies are used to calculate the amplitudes of the blade tip responses. The presence of mistuning in the bladed assembly does not affect the performance of the new techniques.

Forced Harmonic Response of Grouped Blade Systems: Part II—Application

1996 ◽  
Vol 118 (1) ◽  
pp. 137-145 ◽  
Author(s):  
L. F. Wagner ◽  
J. H. Griffin
Keyword(s):  
Numerical Model ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Turbine Blades ◽  
Modal Identification ◽  
Harmonic Response ◽  
Model Based ◽  
Grouped Blades ◽  
Flexible Disk ◽  
Symmetric Structures

The vibration of grouped blades on a flexible disk should, for purposes of economy and clarity of modal identification, be analyzed using procedures developed for cyclically symmetric structures. In this paper, a numerical model, based on the theory of cyclically symmetric structures, is applied to the vibration analysis, and in particular, the harmonic response, of a flexible disk supporting a number of groups, or packets, of turbine blades. Results are presented to show variations in the modal participation factors as a function of such parameters as disk flexibility, blade density, and the total number of assembled groups. It is also shown that many characteristics of the system spectra of natural frequencies are strongly dependent on the number of blade groups.

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