An error correction blade tip-timing method to improve the measured accuracy of blade vibration displacement during unstable rotation speed

Generally, turbine blade vibration can be divided into asynchronous vibration and synchronous vibration. Comparing to parameters identification of asynchronous vibration, that of the synchronous vibration is more difficult and needs more sensors. The applicability of the synchronous identification method is more stringent than that of asynchronous identification method. A new method is presented to identify the blade synchronous vibration parameters based on the blade tip-timing (BTT) method and previous achievements in this region. Here, the parameters, such as the frequency of harmonic resonance center, blade vibration amplitude and the initial phase, are obtained by the nonlinear least square fitting algorithm based on relationships between the rotation speed and the blade tip displacement. We call this way as sweep frequency fitting (SFF) method. As the blade is operated at a constant speed that is near the frequency of resonance center, the blade vibration displacement can be obtained by the sensors at different positions, so the blade synchronous vibration Engine Order (EO) can be obtained by the global autoregressive with instrumental variables (GARIV) method. Furthermore the Campbell diagram of blade synchronous vibration can be plotted by the parameters obtained by GARIV method and SFF method. In the experimental study, the parameter identification of blade synchronous vibration is completed and the Campbell diagram of blade vibration is accurately plotted under the excitation of six magnets. Meanwhile, the experimental study and analysis on the harmonic vibration of blade with different numbers of excitation are carried out. The relative deviation of the dynamic frequency of blade between the experimental result and simulation result is less than 1%.

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Analysis of blade vibration frequencies from blade tip timing data

10.1117/12.885360 ◽

2010 ◽

Cited By ~ 6

Author(s):

Menglin Li ◽

Fajie Duan ◽

Tao Ouyang

Keyword(s):

Vibration Frequencies ◽

Blade Vibration ◽

Timing Data ◽

Blade Tip

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

Volume 11: Structures and Dynamics: Structural Mechanics, Vibration, and Damping; Supercritical CO2 ◽

10.1115/gt2020-14753 ◽

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.

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Blade Tip-timing Technology with Multiple Reference Phases for Online Monitoring of High-speed Blades under Variable-speed Operation

Measurement Science Review ◽

10.1515/msr-2018-0033 ◽

2018 ◽

Vol 18 (6) ◽

pp. 243-250 ◽

Cited By ~ 2

Author(s):

Zhang Ji-wang ◽

Zhang Lai-bin ◽

Ding Ke-Qin ◽

Duan Li-xiang

Keyword(s):

High Speed ◽

Online Monitoring ◽

Rotation Speed ◽

Experimental Tests ◽

Reference Points ◽

Variable Speed ◽

Rotating Shaft ◽

Virtual Reference ◽

Blade Tip ◽

Multiple Reference

Abstract High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.

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An Improved Circumferential Fourier Fit (CFF) Method for Blade Tip Timing Measurements

Applied Sciences ◽

10.3390/app10113675 ◽

2020 ◽

Vol 10 (11) ◽

pp. 3675

Author(s):

Zhibo Liu ◽

Fajie Duan ◽

Guangyue Niu ◽

Ling Ma ◽

Jiajia Jiang ◽

...

Keyword(s):

Development Program ◽

Time Of Arrival ◽

Blade Vibration ◽

Vibration Measurements ◽

Rotating Speed ◽

Resonance Analysis ◽

Rotating Blade ◽

Negative Effect ◽

Frequency Identification ◽

Blade Tip

Rotating blade vibration measurements are very important for any turbomachinery research and development program. The blade tip timing (BTT) technique uses the time of arrival (ToA) of the blade tip passing the casing mounted probes to give the blade vibration. As a non-contact technique, BTT is necessary for rotating blade vibration measurements. The higher accuracy of amplitude and vibration frequency identification has been pursued since the development of BTT. An improved circumferential Fourier fit (ICFF) method is proposed. In this method, the ToA is not only dependent on the rotating speed and monitoring position, but also on blade vibration. Compared with the traditional circumferential Fourier fit (TCFF) method, this improvement is more consistent with reality. A 12-blade assembly simulator and experimental data were used to evaluate the ICFF performance. The simulated results showed that the ICFF performance is comparable to TCFF in terms of EO identification, except the lower PSR or more number probes that have a more negative effect on ICFF. Besides, the accuracy of amplitude identification is higher for ICFF than TCFF on all test conditions. Meanwhile, the higher accuracy of the reconstruction of ICFF was further verified in all measurement resonance analysis.

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On Possibilities of Using Relative Shaft Vibration Signals for Rotating Blades Monitoring

Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines ◽

10.1115/gt2018-76565 ◽

2018 ◽

Author(s):

Jindrich Liska ◽

Vojtech Vasicek ◽

Jan Jakl

Keyword(s):

Steam Turbine ◽

Operating Conditions ◽

Vibration Monitoring ◽

Monitoring Systems ◽

Blade Vibration ◽

Vibration Signals ◽

Rotating Blades ◽

Timing Measurement ◽

Blade Tip ◽

Shaft Vibration

Ensuring the reliability of the steam turbine is the key for its long life. For this purpose monitoring systems are standardly used. Early detection of any failure can avoid possible economical and material losses. A monitoring of rotating blades vibration belongs to the very important tasks of the turbomachinery state assessment. Especially in terms of the last stages of low-pressure part, where the longest blades are vibrating at most. Commonly used methods for blade vibration monitoring are based on contact measurement using strain gauges or non-contact approach based on blade tip timing measurement. Rising demand for low-cost monitoring systems has initiated development of a new approach in blade vibration monitoring task. The presented approach is based on usage of relative rotor vibration signals. Its advantage is in using of standardly installed sensors making this approach economically interesting for the turbine operators compared to the traditionally used methods, mentioned above. This paper summarizes the symptoms of blade vibration phenomenon in relative shaft vibration signals, the impact of operating conditions on the blade vibration amplitude and its comparison to blade tip-timing measurement results. In addition of several examples, the article also describes an evaluation of proposed method in operation of steam turbine with power of 170MW.

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Rotating blades monitoring using standard turbine instrumentation

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406219889084 ◽

2019 ◽

Vol 233 (23-24) ◽

pp. 7447-7458

Author(s):

Jindrich Liska ◽

Jan Jakl ◽

Vojtech Vasicek

Keyword(s):

Steam Turbine ◽

Low Cost ◽

Actual State ◽

Blade Vibration ◽

Stress Evaluation ◽

New Approach ◽

Rotating Blades ◽

Low Pressure Turbine ◽

Blade Tip ◽

Proper Operation

Ensuring the reliability of the steam turbine is fundamental task for its proper operation. Early detection of any failure avoids material and financial losses. A very important task in turbomachinery diagnostics is monitoring of rotating blades vibration, especially in terms of the last stages of low-pressure turbine parts, where, in general, the vibration can reach the important level due the blades length. The commonly used methods are based on stress evaluation using strain gauges or on the non-contact measurement of blade tips – blade tip-timing (BTT) method. Rising demand for low-cost monitoring systems suitable for blade monitoring has led to development of a new approach based on signal processing of standard turbine instrumentation. The symptoms of blade vibration could be also visible in signals from relative shaft vibration (SV) sensors, which are standardly installed in turbine journal bearings. This paper illustrates the principles and possibilities of the approach based on processing of SV signals for monitoring of actual state of rotating blades. Finally, the comparison of parallel measurements using SV and BTT in operation of steam turbine reveals the properties and advantages of both methods.

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Numerical Investigation of Tip Clearance Flow Induced Flutter in an Axial Research Compressor

Volume 7B: Structures and Dynamics ◽

10.1115/gt2016-56956 ◽

2016 ◽

Cited By ~ 1

Author(s):

Daniel Möller ◽

Maximilian Jüngst ◽

Felix Holzinger ◽

Christoph Brandstetter ◽

Heinz-Peter Schiffer ◽

...

Keyword(s):

Early Stage ◽

Rotor Blades ◽

Tip Clearance ◽

Blade Vibration ◽

Tip Clearance Flow ◽

Transonic Compressor ◽

Clearance Flow ◽

Fluctuation Pattern ◽

Blade Tip ◽

Pass Through

A flutter phenomenon was observed in a 1.5-stage configuration at the Darmstadt transonic compressor. This phenomenon is investigated numerically for different compressor speeds. The flutter occurs for the second eigenmode of the rotor blades and is caused by tip clearance flow which is able to pass through multiple rotor gaps at highly throttled operating points. The vibration pattern during flutter is accompanied by a pressure fluctuation pattern of the tip clearance flow which is interacting with the blade motion causing the aeroelastic instability. The velocity of the tip clearance flow fluctuation is about 50% of the blade tip speed for simulation and experiment and also matches the mean convective velocity inside the rotor gap. This is consistent for all compressor speeds. From this investigations, general guidelines are drawn which can be applied at an early stage during compressor design to evaluate the susceptibility to this kind of blade vibration.

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A Non-Uniformly Under-Sampled Blade Tip-Timing Signal Reconstruction Method for Blade Vibration Monitoring

Sensors ◽

10.3390/s150202419 ◽

2015 ◽

Vol 15 (2) ◽

pp. 2419-2437 ◽

Cited By ~ 29

Author(s):

Zheng Hu ◽

Jun Lin ◽

Zhong-Sheng Chen ◽

Yong-Min Yang ◽

Xue-Jun Li

Keyword(s):

Signal Reconstruction ◽

Vibration Monitoring ◽

Reconstruction Method ◽

Blade Vibration ◽

Blade Tip

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The Use of Eddy Current Sensors for the Measurement of Rotor Blade Tip Timing: Sensor Development and Engine Testing

Volume 2: Controls, Diagnostics and Instrumentation; Cycle Innovations; Electric Power ◽

10.1115/gt2008-50792 ◽

2008 ◽

Cited By ~ 6

Author(s):

D. N. Cardwell ◽

K. S. Chana ◽

P. Russhard

Keyword(s):

Eddy Current ◽

Rotor Blade ◽

Service Use ◽

Optical Systems ◽

Current Sensor ◽

Blade Vibration ◽

Arrival Times ◽

Eddy Current Sensor ◽

Blade Tip ◽

Engine Testing

The advent of tip-timing systems makes it possible to assess turbomachinery blade vibration using non-contact systems. Currently, the most widely used systems in industry are optical systems. However, these systems are still only used on development engines, largely because of contamination problems from dust, dirt, oil, water etc. Further development of these systems for in-service use is problematic because of the difficulty of eliminating contamination of the optics. Hence, alternatives need to be developed that are immune to contamination but have equivalent resolution and bandwidth as the optical system. Experimental measurements have been carried out using alternative sensors. An eddy current sensor has been developed in a series of laboratory and engine tests to measure rotor blade arrival times. Comparisons are made with an industry standard optical blade tip timing system. The results show that it is possible to acquire high quality blade tip timing data for use in engine condition monitoring using an eddy current sensor. This sensor allows measurements to be taken that do not suffer from flow contamination and allow deployment for hotter flow environments.

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