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

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 761 ◽  
Author(s):  
Jiang Wu ◽  
Bin Wen ◽  
Yu Zhou ◽  
Qi Zhang ◽  
Shuiting Ding ◽  
...  
Keyword(s):  
Response Time ◽  
Eddy Current ◽  
Tip Clearance ◽  
Current Sensor ◽  
Data Set ◽  
Eddy Current Sensor ◽  
Adjustment Model ◽  
Blade Tip ◽  
Speed Adjustment ◽  
Blade Tip Clearance

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.

Investigation on the Turbine Blade Tip Clearance Measurement and Active Clearance Control Based on Eddy Current Pulse-Trigger Method

2017 ◽  
Author(s):  
Weimin Wang ◽  
Huajin Shao ◽  
Xing Shao ◽  
Kailiang Song
Keyword(s):  
Experimental Study ◽  
Control System ◽  
Eddy Current ◽  
Axial Displacement ◽  
Tip Clearance ◽  
Current Sensor ◽  
Non Linear ◽  
Blade Tip ◽  
Clearance Control ◽  
Blade Tip Clearance

Blade tip clearance (BTC) measurement and active clearance control (ACC) have been and continue to be a fundamental concern in turbomachinery, which are closely bound up with the efficiency and reliability. This paper addresses the BTC measurement and ACC experimental study based on eddy current pulse-trigger method (ECPTM). And the implementation of ACC by axial displacement of the blisk is novel and this paper is the first to present the technique. The purpose of this paper is three fold. The first portion of this paper addresses the BTC measurement in different rotating speeds based on the larger scale rig, where a high-bandwidth (100 kHz) eddy current sensor (HECS) is employed. The results show that the relative errors of BTC values are not much bigger than 20%. The result indicates that ECPTM is more generally applicable in the condition where the eddy current sensor (ECS) is insufficient sampling caused by the limit of narrow bandwidth, especially under the high linear velocity condition. The second portion of this paper describes the ACC system where an electro-hydraulic proportional position control system (EHPPCS) is employed as the actuator. EHPPCS has the advantages of small size, fast response, resistance to load stiffness, large output and simple operation, which is widely applicable to the automatic control system of industrial power. This system optimizes the geometry shapes of casing and the blade tips to create a linear relationship of BTC values related to the axial displacement of the rotor. The BTC values can be transferred into axial displacement of the rotor, and then a voltage/current-BTC values characteristic can be obtained by employing EHPPCS in different rotating speeds. Unfortunately, one of the core components of EHPPCS is an overflow valve with a non-linear and time-variable voltage/current-pressure characteristic. Besides, the pressure-axial displacement characteristic of tilting pad thrust bearing is also non-linear. All those non-linear characteristics make it unsatisfactory to use the conventional PID control algorithm to achieve effective control of the system, which cause many difficulties in controlling of axial displacement of the rotor. So the last portion of this paper is the experimental study on ACC based on the above system by adopting sliding mode adaptive control of nonlinear system (SMACNS). The BTC values have been obtained under different outlet pressures by changing the current in different rotating speeds. The results indicate that this approach has nice robustness and smooth controlled quantity, and can overcome the difficulty caused by nonlinearity, parameter uncertainty and load disturbance. And then, the precision verification and error analysis are made. However, this work is a proof-of-concept demonstration using a laboratory setup providing the basis for BTC active control and blade health monitoring (BHM) based on ECS.

scholarly journals Simulating eddy current sensor outputs for blade tip timing

2018 ◽  
Vol 10 (1) ◽  
pp. 168781401774802 ◽  
Author(s):  
Nidhal Jamia ◽  
Michael I Friswell ◽  
Sami El-Borgi ◽  
Ralston Fernandes
Keyword(s):  
Eddy Current ◽  
Tip Clearance ◽  
Vibration Measurement ◽  
Current Sensor ◽  
Contactless Method ◽  
Diagnostic Features ◽  
Blade Vibration ◽  
Eddy Current Sensor ◽  
Blade Tip ◽  
Current Sensors

Blade tip timing is a contactless method used to monitor the vibration of blades in rotating machinery. Blade vibration and clearance are important diagnostic features for condition monitoring, including the detection of blade cracks. Eddy current sensors are a practical choice for blade tip timing and have been used extensively. As the data requirements from the timing measurement become more stringent and the systems become more complicated, including the use of multiple sensors, the ability to fully understand and optimize the measurement system becomes more important. This requires detailed modeling of eddy current sensors in the blade tip timing application; the current approaches often rely on experimental trials. Existing simulations for eddy current sensors have not considered the particular case of a blade rotating past the sensor. Hence, the novel aspect of this article is the development of a detailed quasi-static finite element model of the electro-magnetic field to simulate the integrated measured output of the sensor. This model is demonstrated by simulating the effect of tip clearance, blade geometry, and blade velocity on the output of the eddy current sensor. This allows an understanding of the sources of error in the blade time of arrival estimate and hence insight into the accuracy of the blade vibration measurement.

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

2008 ◽  
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.

Investigation on the Turbine Blade Tip Clearance Monitoring Based on Eddy Current Pulse-Trigger Method

2016 ◽  
Author(s):  
Weimin Wang ◽  
Huajin Shao ◽  
Lifang Chen ◽  
Huibin Song
Keyword(s):  
Turbine Blade ◽  
Eddy Current ◽  
Tip Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Rotating Speed ◽  
Laboratory Setup ◽  
Blade Tip ◽  
Scale Test ◽  
Blade Tip Clearance

The efficiency and reliability of turbomachinery will be improved by blade tip clearance (BTC) and blade tip timing (BTT) monitoring. Several types of sensors such as eddy-current, capacitance and optical probes are used to realize this objective. Eddy current sensor (ECS) is an ideal choice with its advantage of durablity and that it is unaffected by gas stream properties such as contamination, water vapor, and moisture. However, the bandwidth of ECS is usually less than 100 kHz, which will limit the resolution of the monitoring result. In this paper, a pulse-trigger technology based BTC method was presented. This method optimizes the static radial and circumferential calibration technology to obtain the sensitivity of the ECS in the different relative locations against the tip of blade. The information from the clearance sensor will be fused with that from the once per revolution (OPR) or key phase sensor. The method is more generally applicable in the condition where the ECS is insufficient sampling caused by the limit of narrow bandwidth, especially under the high blade tip velocity condition. A small scale and larger scale BTC measurement rig are established to validate the feasibility of this method. The small one is easy to calibrate with high accuracy and can be used to illustrate the performance of the method, while the larger scale test rig is close to real industry turbine blade. In this apparatus, the axial displacement and radial displacement of rotor vibration as well as the clearance can be monitored together so that further investigation can be conducted. Experimental research was carried out on both test rig at different rotating speed. The results show that the method presented in this paper can improve the accuracy of tip clearance monitored by ECS very well. Furthermore, this work is a proof-of-concept demonstration using a laboratory setup providing the basis for BTC active control and blade health monitoring (BHM) based on ECS.

Verification and Design of High Precision Eddy Current Sensor for Tip Clearance Measurement

2018 ◽  
Author(s):  
Ziyu Zhao ◽  
Zhenxia Liu ◽  
Yaguo Lyu ◽  
Xinxin Xu
Keyword(s):  
High Precision ◽  
Eddy Current ◽  
High Sensitivity ◽  
Response Speed ◽  
Measurement Range ◽  
Tip Clearance ◽  
Current Sensor ◽  
Eddy Current Sensor ◽  
Planar Coil ◽  
Sensor Coil

A high precision eddy current sensor for tip clearance measurement was proposed to assess the dynamic tip clearance measurement for aero-engine rotator. Based on the Lenz’s law, the eddy current sensor has high sensitivity, quick response speed and strong anti-interference capability, in addition, the simple geometry and easy installation are its main merits. The aim is to study the influence of planar coil structure parameters and excitation signal parameters on the sensor coil measurement, provide the basis for design of practical sensor in turbine tip clearance measurement. The dynamic calibration experiment verified the designed planar sensor coil, the results indicated the sensor resolution was 10μm and the measurement range was not less than 3mm. The dynamic experiment proved the measuring range, resolution, response speed of designed sensor can meet the requirement of turbine blade tip clearance measurement. The work provides experience in eddy current sensor design in different application, not only in turbine. And the future work will focus on the high temperature issues.

scholarly journals High-Precision Extraction Method for Blade Tip-Timing Signal with Eddy Current Sensor

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Ji-wang Zhang ◽  
Ke-qin Ding ◽  
Guang Chen
Keyword(s):  
Measurement Error ◽  
Eddy Current ◽  
Background Noise ◽  
High Speed ◽  
Ensemble Empirical Mode Decomposition ◽  
Tip Clearance ◽  
Mode Decomposition ◽  
Blade Tip ◽  
The Asymmetry ◽  
Blade Tip Clearance

Online monitoring of high-speed rotating blades has always been a hot topic. Of the various methods, the blade tip timing (BTT) technique, based on eddy current sensors, is considered to be the most promising. However, BTT signals are easily influenced by various factors, which means that the accurate extraction of BTT signals remains a challenge. To try to solve this problem, the causes of measurement error were analyzed. The three main reasons for the error were established: the variation in blade tip clearance, the interference of background noise, and the asymmetry of the blade tip shape. Further, pertinent improvement methods were proposed, and a compensation method was proposed for the errors caused by the variation of tip clearance. A new denoising and shaping algorithm based on ensemble empirical mode decomposition (EEMD) was introduced for the errors caused by background noise. Additionally, an optimal installation position of the sensor was also proposed for the errors caused by the asymmetry of the blade tip shape. Finally, simulations and experiments were used to demonstrate the improved methodology. The results show that the measurement error on vibration amplitude and vibration frequency using the proposed method is less than 2.89% and 0.17%, respectively, which is much lower than the traditional method (24.44% and 0.39%, respectively).

The Development of a Hot Section Eddy Current Sensor for Turbine Tip Clearance Measurement

2013 ◽  
Author(s):  
K. S. Chana ◽  
M. T. Cardwell ◽  
J. S. Sullivan
Keyword(s):  
Eddy Current ◽  
Gas Turbines ◽  
High Speed ◽  
Elevated Temperatures ◽  
Tip Clearance ◽  
Test Facility ◽  
Current Sensor ◽  
Integrated Sensor ◽  
Eddy Current Sensor ◽  
Turbine Efficiency

Gas turbine efficiency can be improved with tighter turbine tip clearances. An approach being developed by engine manufacturers deploys active tip clearance monitoring where the turbine casing diameter is actively controlled in-service either mechanically or thermally. Typically current engines operate at about 1% clearance of blade span. With active control this could potentially be reduced significantly. Ideally active tip clearance control requires closed loop feedback measurements to maintain very small clearances without the risk of blade tip contact with the casing liner. Therefore reliable and robust sensors systems are required that can operate at the elevated temperatures found in modern gas turbines. Currently there are limited sensor systems available that can operate at these temperatures and survive typical sensor life requirements of many thousands of hours. This study details development of a high temperature eddy current sensor system for hot section applications. The investigation encompasses development and validation of an integrated sensor design to provide tip clearance measurements. The sensor is designed to withstand temperatures of order 1500 to 1600K. Test facilities used to validate the system include a RB168 Mk 101 Spey engine and a Rolls-Royce VIPER engine. The turbine casings of both engines were modified to fit sensors directly above the rotor. The accuracy of the system was validated in a high speed rotor test facility with engine representative blading. Accuracy of the eddy current sensor was compared and validated against a dynamic laser micrometer system.

Tip-Clearance Measurements on an Engine High Pressure Turbine Using an Eddy Current Sensor

2017 ◽  
Author(s):  
V. Sridhar ◽  
K. S. Chana
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Gas Turbine ◽  
Eddy Current ◽  
Health Monitoring ◽  
Tip Clearance ◽  
Current Sensor ◽  
High Pressure Turbine ◽  
Eddy Current Sensor ◽  
Health Monitoring Systems

Gas turbine health monitoring is an important area of research. As the performance of aircraft and power plants increase, they will require better sensors for health monitoring systems to prevent failures. Health monitoring systems help in preventive maintenance reducing unnecessary downtime and maintenance costs. Gas turbine blades are subjected to dynamic loads caused by rotor imbalances, distortions in the intake flows etc. These loads cause low or high cycle fatigues and the blades can fail over time. Tip-timing and tip-clearance systems makes it possible to assess turbomachinery blade vibration by using non-contact measurement systems such as optical, eddy current, hall effect, capacitve etc. The most widely used systems in industry are optical, however, these systems are still largely prone to contamination problems from dust, dirt, oil, water etc. Further development of these systems for in-service use is problematic because of the difficulty in eliminating contamination of the optics. Other systems, although immune to contamination, may not be able to measure both tip-clearance and tip-timing at the same time due to their operating principle. Another limitation is that they cannot be used in high temperature applications such as in a high pressure turbine where the temperatures can reach 1400°C. Eddy current sensors are found to be quite robust and can measure both tip-timing and tip-clearance. They are currently being used for gas turbine health monitoring applications at low temperatures such as in the compressor stage and last stage of a steam turbine. A new high temperature eddy current sensor has been developed in-house at the University of Oxford for application in gas turbine tip-timing and tip clearance measurements to assess blade vibrations. The current sensor is a modified version of the existing eddy current sensor that is able to operate at high temperatures of about 1400°C. The paper presents the development of the sensor and experimental results of tip clearance measurements in the high pressure turbine stage of a jet engine. In the engine tests, two blades were reduced in height to increase the tip-clearance and the measurements were taken at both idle and max operating speeds. The sensor was found to work in these harsh environments and was sufficiently sensitive to accurately determine the tip clearance at these elevated temperatures. Tests were carried out mainly to demonstrate the technique of obtaining good tip clearance measurements and the survivability of the sensors in the high temperature and pressure environment.

Inspection of Surface Rolled Sintered Gears using Eddy-Current Sensor

2013 ◽  
Vol 133 (5) ◽  
pp. 300-306
Author(s):  
Tsutomu Mizuno ◽  
Yuichi Asato ◽  
Sho Goto ◽  
Takashi Watanabe ◽  
Teruie Takemasu ◽  
...  
Keyword(s):  
Eddy Current ◽  
Current Sensor ◽  
Eddy Current Sensor
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