Calibration of blade tip-timing sensor for shrouded 40″ last stage blade

Kubin, Zdenek; Míšek, T.; Hlous, Jan; Dadáková, Tereza; Kellner, Josef; Bachorec, T.

doi:10.1016/j.ymssp.2018.02.001

Cited by 17 publications

(8 citation statements)

References 5 publications

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“…However, the minimal clearance existing between the moving blades with high speed and the static cabinet is not able to be directly measured by conventional approaches. Recently, quite a number of novel methods for fast and accurate BTC measurement have been developed, such as optical methods [ 13 , 14 , 15 , 16 ] based on the intensity modulation of the reflected light, capacitance method [ 17 , 18 , 19 , 20 ] by constructed capacitance between the cabinet and blade tip, eddy current method [ 21 , 22 , 23 ] by installing the sensor coil probe in the cabinet to form an eddy current on the blade tip surface, and the microwave method [ 24 , 25 , 26 ] based on the principle, which is similar to a short range radar system. At present, optical methods and capacitance methods are widely used [ 27 , 28 , 29 , 30 ], generally at the R&D stage of engine.…”

Section: Introductionmentioning

confidence: 99%

“…This makes that the response frequency of the measurement loop changes with the measured clearance. Actually, as two significant performance indicators, signal-to-noise ratio (SNR) and response frequency are contradictory [ 21 ], specifically, more coil turns determine larger signal amplitude and laggard response, fewer coil turns make the SNR unsatisfactory. Consequently, the measured clearance, SNR and response frequency require being considered comprehensively in ECS design.…”

Section: Introductionmentioning

confidence: 99%

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Eddy Current Sensor System for Blade Tip Clearance Measurement Based on a Speed Adjustment Model

Wen

Zhou

et al. 2019

Sensors

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Blade tip clearance (BTC) measurement and active clearance control (ACC) are becoming crucial technologies in aero-engine health monitoring so as to improve the efficiency and reliability as well as to ensure timely maintenance. Eddy current sensor (ECS) offers an attractive option for BTC measurement due to its robustness, whereas current approaches have not considered two issues sufficiently. One is that BTC affects the response time of a measurement loop, the other is that ECS signal decays with increasing speed. This paper proposes a speed adjustment model (SAM) to deal with these issues in detail. SAM is trained using a nonlinear regression method from a dynamic training data set obtained by an experiment. The Levenberg–Marquardt (LM) algorithm is used to estimate SAM characteristic parameters. The quantitative relationship between the response time of ECS measurement loop and BTC, as well as the output signal and speed are obtained. A BTC measurement method (BTCMM) based on the SAM is proposed and a geometric constraint equation is constructed to assess the accuracy of BTC measurement. Experiment on a real-time BTC measurement during the running process for a micro turbojet engine is conducted to validate the BTCMM. It is desirable and significative to effectively improve BTC measurement accuracy and expand the range of applicable engine speed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Eddy Current Sensor System for Blade Tip Clearance Measurement Based on a Speed Adjustment Model

Wen

Zhou

et al. 2019

Sensors

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“…They also performed MFL testing experiments for steel pipes to confirm the effect of the MIEC. More recently, Kubín et al [30] modelled the magnetic interference between ECS and a blade shroud. They proposed a methodology to choose the size of a BTT sensor and where to place this sensor, and they verified their approach through test rig measurements.…”

Section: Introductionmentioning

confidence: 99%

Modelling and experimental validation of active and passive eddy current sensors for blade tip timing

Jamia

Friswell

El-Borgi

et al. 2019

Sensors and Actuators A: Physical

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To monitor the vibration of blades in rotating machinery, the contactless method called Blade Tip Timing (BTT) is widely used. Blade vibration and clearance are important diagnostic features for condition monitoring, including the detection of blade cracks. To perform the BTT technique, optical sensors were widely used by industry due to their high accuracy, but the main drawback of these systems is their low tolerance to the presence of contaminants. To overcome this downside, eddy current sensors are a good alternative for health monitoring applications in gas turbines due to their insensitivity to contaminants and debris. This type of sensor has been used by many researchers, predominantly on the experimental side to investigate BTT systems and there is a lack of modelling to support the measurement system design. This paper fills the gap between experiments and modelling for the particular case of a blade rotating past eddy current sensors. Hence the novelty of this paper is the simulation of the BTT application using detailed quasi-static finite element models of the electromagnetic field to estimate the outputs from active and passive eddy current sensors. A test rig composed of a bladed disk with 12 blades clamped to a rotating shaft was designed and manufactured in order to validate the proposed models with experimental measurements. Finally, a parametric study is presented to show the effect of the blade tip clearance and the rotational speed on the accuracy of the BTT measurement. This leads to better understanding of the sources of error in the time of arrival of the blades passing the sensor and hence insight into the blade vibration measurement accuracy.

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“…Kubín at the University of West Bohemia in Pilsen, performed BTT measurements in power stations and investigated the calibration of tip timing sensors using passive eddy current sensors for shrouded blades. An optical sensor from HoodTech Corporation was also used in the test rig as reference for a quick overview of exiting [19]. The best sensor axial position was calculated and verified by the FEM model and experiment.…”

Section: Introductionmentioning

confidence: 99%

Synchronous Vibration Measurements for Shrouded Blades Based on Fiber Optical Sensors with Lenses in a Steam Turbine

Duan

Jiang

et al. 2019

Sensors

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It is important to obtain accurate dynamic vibrations of steam turbine blades for safe operation. Strain gauge (SG) measurements cannot fully obtain vibrations of all blades and nodal diameter (ND) details. The blade tip timing (BTT) technique could resolve this problem because it has the advantage of measuring all blades’ vibrations. This article proposed an improved BTT technique for measuring synchronous vibrations of shrouded blades in a steam turbine based on fiber optical sensors with lenses. The newly developed sensor was equipped with a Plano-convex lens, and the optical path was specifically designed to collimate the beam within a large working distance from 4 to 19 mm and improve the measuring accuracy. A method to search the spectra of all peak vibration amplitudes of all the blades was proposed to obtain the ND details of synchronous vibration. Experimental results validated the efficiency and accuracy of the proposed methods and sensors. Comparison results of BTT measurements with SG measurements showed that the relative errors of normalized frequency and strain were small and acceptable.

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Calibration of blade tip-timing sensor for shrouded 40″ last stage blade

Cited by 17 publications

References 5 publications

Eddy Current Sensor System for Blade Tip Clearance Measurement Based on a Speed Adjustment Model

Eddy Current Sensor System for Blade Tip Clearance Measurement Based on a Speed Adjustment Model

Modelling and experimental validation of active and passive eddy current sensors for blade tip timing

Synchronous Vibration Measurements for Shrouded Blades Based on Fiber Optical Sensors with Lenses in a Steam Turbine

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