Tip-Timing Data Analysis for Mistuned Bladed Discs Assemblies

2008 ◽  
Author(s):  
Cyrille Ste´phan ◽  
Marc Berthillier ◽  
Joseph Lardie`s ◽  
Arnaud Talon
Keyword(s):  
Spectral Analysis ◽  
Optical Sensors ◽  
Fundamental Problem ◽  
Spectral Estimation ◽  
Minimum Variance ◽  
Vibration Measurement ◽  
Blade Vibration ◽  
Autocorrelation Matrix ◽  
Timing Data ◽  
Blade Tip

In turbomachine industry, bladed assembly vibration measurements are very important for blades behaviour estimation. These measurements are generally obtained from strain gauges. However, one of the most promising methods for the analysis of blade vibrations in rotating bladed assemblies is the Blade Tip Timing or Optical Blade Vibration Measurement method. A set of optical sensors is mounted on an engine casing, in front of a disc, and measures the times of arrival of each blade. These timings are then used to compute the vibrations of the blades. However the fundamental problem for spectral analysis of blade tip timing data is that the signals are undersampled and aliased. We propose here a new method for spectral estimation of blades responses from tip timing data that overcome these difficulties. The method proposed in this communication is based on the use of a minimum variance filter associated with an iterative updating of the autocorrelation matrix. That allows to process correctly a signal even if the number of known signal samples is less than equivalent Nyquist criterion. This approach is suitable for spectral analysis of undersampled and aliased signals. Perfomances of the spectral estimator have been evaluated for one simulated and one experimental test cases. The method seems very promising for the monitoring of mistuned bladed discs.

A Discussion on the Advancement of Blade Tip Timing Data Processing

2017 ◽  
Author(s):  
Vsevolod Kharyton ◽  
Grigorios Dimitriadis ◽  
Colin Defise
Keyword(s):  
Digital Signal ◽  
Minimum Variance ◽  
Rotating Stall ◽  
Blade Vibration ◽  
Variable Threshold ◽  
Engine Order ◽  
Timing Data ◽  
Large Scope ◽  
Blade Tip ◽  
Frequency Aliasing

The Blade Tip Timing method (BTT) is a well-known approach permitting individual blade vibration behavior characterization. The technique is becoming increasingly popular among turbomachinery vibration specialists. Its advantages include its non-intrusive nature and its capability of being used for long-term monitoring, both in on-line and offline analysis. However, the main drawback of BTT is frequency aliasing. Frequency aliasing effects in tip timing can be reduced by means of the application of different methods from digital signal analysis that can exploit the non-uniform nature of the data sampled by BTT. This non-uniformity is due to the fact that an optimization of the circumferential distribution of BTT probes is usually required in order to improve the data quality for targeted modes of blade vibration and/or orders of excitation. The BTT data analysis methods considered in this study are the non-uniform Fourier transform, the minimum variance spectrum estimator approach, a multi-channel technique using in-between samples interpolation, the Lombe-Scargle periodogram and an iterative variable threshold procedure. These methods will be applied to measured data representing quite a large scope of events occurring during gas-turbine compressor operation, e.g. synchronous engine order resonance crossing, rotating stall, suspected limit-cycle oscillations. Finally, the frequency estimates obtained from all these methods will be summarized.

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 Standard Sine Fitting Algorithms Applied To Blade Tip Timing Data

2014 ◽  
Vol 30 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Krzysztof Kaźmierczak ◽  
Radosław Przysowa
Keyword(s):  
A Priori ◽  
Measurement Data ◽  
Time Of Arrival ◽  
Blade Vibration ◽  
Indirect Methods ◽  
Non Linear ◽  
Timing Data ◽  
Blade Tip ◽  
Vibration Parameters ◽  
Signal Processing Methods

Abstract Blade Tip Timing (BTT) is a non-intrusive method to measure blade vibration in turbomachinery. Time of Arrival (TOA) is recorded when a blade is passing a stationary sensor. The measurement data, in form of undersampled (aliased) tip-deflection signal, are difficult to analyze with standard signal processing methods like digital filters or Fourier Transform. Several indirect methods are applied to process TOA sequences, such as reconstruction of aliased spectrum and Least-Squares Fitting to harmonic oscillator model. We used standard sine fitting algorithms provided by IEEE-STD-1057 to estimate blade vibration parameters. Blade-tip displacement was simulated in time domain using SDOF model, sampled by stationary sensors and then processed by the sinefit.m toolkit. We evaluated several configurations of different sensor placement, noise level and number of data. Results of the linear sine fitting, performed with the frequency known a priori, were compared with the non-linear ones. Some of non-linear iterations were not convergent. The algorithms and testing results are aimed to be used in analysis of asynchronous blade vibration.

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.

A blade tip-timing method without once-per-revolution sensor for blade vibration measurement in gas turbine engines

2020 ◽  
Author(s):  
Chengwei Fan ◽  
Yadong Wu ◽  
Pete Russhard ◽  
Can Ruan ◽  
Anjenq Wang
Keyword(s):  
Gas Turbine ◽  
Resonance Region ◽  
Operating Conditions ◽  
Vibration Measurement ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Rotor Speed ◽  
Blade Vibration ◽  
Reference Probe ◽  
Blade Tip

The blade vibration measurement is crucial for gas turbine engines in order to ensure safe operations. One of the techniques is blade tip-timing (BTT), which is under the assumption that rotor speed is constant and depends on a once-per-revolution (OPR) timing reference to calculate the blade tip displacement, and identifying the blade sequence. However, this assumption is incorrect for transient conditions, and the installation of OPR sensor sometimes is not allowable and reliable. These reasons greatly limit the application of BTT technique. This paper proposes a self-correcting (SC) BTT method to realize the blade vibration measurement under different operating conditions without using the OPR sensor, which is based on the polynomial fitting and a reference probe is used to correct high-order fitting coefficients. Numerical results show that the SC-BTT method can greatly reduce the fitting error caused by blade pitch and vibrational parameters. Experimental results demonstrate that the proposed technique is capable of removing the limitation of the lack of OPR sensor and overcoming the drawbacks of OPR system, such as the failure of OPR sensor or low-speed resolution. For three investigated cases, the relative errors of derived rotor speed are below 0.12%. The relative error of blade peak-to-peak amplitude (PPA) and the initial phase angle are around 3% at the resonance region with engine order (EO) 2.

Efficient Generation of Engine Representative Tip Timing Data Based on a Reduced Order Model for Bladed Rotors

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Felix Figaschewsky ◽  
Benjamin Hanschke ◽  
Arnold Kühhorn
Keyword(s):  
Real Data ◽  
Data Generation ◽  
Simulation Environment ◽  
Blade Vibration ◽  
Compressor Rotor ◽  
Positioning Errors ◽  
System A ◽  
Sample Data ◽  
Timing Data ◽  
Blade Tip

In modern compressors, the assessment of blade vibration levels as well as health monitoring of the components are fundamental tasks. Traditionally, this assessment is done by the application of strain gauges (SG) to some blades of the assembly. In contrast to SGs, blade tip timing (BTT) offers a contactless monitoring of all blades of a rotor and there is no need of a telemetry system. A major issue in the interpretation of BTT data is the heavily undersampled nature of the signal. Usually, newly developed BTT algorithms are tested with sample data created by simplified structural models neglecting many of the uncertainties and disturbing influences of real applications. This work focuses on the creation of simulated BTT datasets as close as possible to real case measurements. For this purpose, a subset of nominal system modes (SNM) representation of a compressor rotor is utilized. This model is able to include a large number of features present in real measurements, such as mistuning, static blade deflections due to centrifugal loads, aerodynamic damping, and multiple mode resonances. Additionally, manufacturing deviations of the blade geometry, probe positioning errors (PPEs) in the BTT system, and noise in the time of arrivals (TOAs) are captured by the BTT simulation environment. The main advantage of the created data is the possibility to steadily increase the signal complexity. Starting with a “perfect” signal the simulation environment is able to add different uncertainties one after the other. This allows the assessment of the influence of different features occurring in real measurements on the performance and accuracy of the analysis algorithms. Finally, a comparison of simulated BTT data and real data acquired from a rig test is shown to validate the presented approach of BTT data generation.

scholarly journals A Torsional Vibration Measurement Method for Rotating Blades Based on Blade Tip Timing

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Haonan Guo ◽  
Yongmin Yang ◽  
Fengjiao Guan ◽  
Haifeng Hu ◽  
Guoji Shen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Torsional Vibration ◽  
Measurement Method ◽  
Optimization Method ◽  
Vibration Monitoring ◽  
Vibration Measurement ◽  
Stable Operation ◽  
Blade Vibration ◽  
Blade Tip ◽  
Types Of Faults

During the working process of the turbine, some types of faults can cause changes in the vibration characteristics of the blades. The real-time vibration monitoring of the blades is of great significance to the stable operation and state-based maintenance. Torsional vibration is a kind of blade vibration modes and results in failures such as cracks easily. Thus, it is important to measure it due to the harmfulness of torsional vibration. Firstly, the principle of blade tip timing (BTT) is introduced, and the models of the blade are built to analyze the characteristics of torsional vibration. Then, the compressed sensing theory is introduced, and its related parameters are determined according to the measurement requirements. Next, based on the condition that the blade rigidity axis is not bent and bent, respectively, the layout method of sensors is proposed and the numerical simulation of the measurement process is performed. The results of the above two types of numerical simulation verify the proposed measurement method. Finally, by analyzing the influencing factors of measurement uncertainty, the optimization method of sensors’ layout is further proposed. This study can provide important theoretical guidance for the measurement of blade torsional vibration.

Comparative Study Between In-Situ Measured Vibration Data at Bearing and BTT on a LP Turbine Last Stage Blades in a Steam Turbo-Generator Set

2013 ◽  
Author(s):  
W. Hahn ◽  
Jyoti K. Sinha
Keyword(s):  
Vibration Measurement ◽  
Blade Vibration ◽  
Vibration Data ◽  
Turbo Generator ◽  
The Status ◽  
Blade Tip ◽  
Last Stage ◽  
Run Up ◽  
Lp Turbine

Cracking of the last stage blades of the low pressure (LP) turbines has been observed after 2007 in the 2 steam turbo-generator (TG) units out of the 4 units at the West Burton Power Plant UK. These 2 units were retrofitted with the new design LP rotor including blades in 1995 and 1997. Recent vibration measurements during machine transient and steady state operations confirms that the TG sets are running close to the machine critical speed and the blades are expected to have high vibration. Now the Unit 3 is fitted with the blade tip timing (BTT) system to monitor the LP1 last stage blades. Hence the present effort to compare the vibration of the blades by the BTT system with the bearing vibration to establish the correlation such that the status of the blade vibration can be accessed even without BTT measurement and the correlation may be used for other units with similar dynamics. The paper presents the comparison of the in-situ vibration measurement on bearings during machine run-up with online BTT data, observations, and possible correlation.

New Possibilities for Analyzing Complex Asynchronous Blade Vibrations From Tip-Timing Data Using a Sparse Spectral Analysis Method

2019 ◽  
Author(s):  
Antoine Bouchain ◽  
José Picheral ◽  
Elisabeth Lahalle ◽  
Agathe Vercoutter ◽  
Bertrand Burgardt ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Spectral Estimation ◽  
Estimation Methods ◽  
Measurement Technology ◽  
Test Case ◽  
Engine Operation ◽  
Time Frequency ◽  
Mechanical Responses ◽  
Blade Vibrations ◽  
Timing Data

Abstract Measurements in engine operation provide key information for understanding the blades vibrating behaviors, especially while observing complex asynchronous vibrations, such as flutter. The studied vibration is performed by the spectral analysis of the measured vibrating mechanical responses. In this context, tip-timing measurement technology enables to get a large amount of information as it monitors all the blades. However, tip-timing technology generates sub-sampled and non-uniform sampled signals. Thus, conventional spectral estimation methods lead to aliased frequency components on the spectrum. Therefore, specific estimation methods have been developed to overcome this issue. This paper presents the tip-timing measurements analysis of a non synchronous vibration test case. It uses a new sparse method with block-OMP algorithm in order to estimate time-frequency diagrams of each blade separately. The results are compared to the results of the well-known asynchronous tip-timing method, called All Blade Spectrum. This real test case highlights the limitations of the latter method, as it involves too much uncertainty, while the sparse method with block-OMP enables to characterize these complex asynchronous blade vibrations.

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