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).

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.

scholarly journals An Optical Fiber Measurement System for Blade Tip Clearance of Engine

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Jia Binghui ◽  
He Lei
Keyword(s):  
Optical Fiber ◽  
Measurement System ◽  
High Speed ◽  
Dynamic Performance ◽  
Measurement Range ◽  
Tip Clearance ◽  
Processing Unit ◽  
Blade Tip ◽  
Optical Fiber Measurement ◽  
Blade Tip Clearance

The benefits of reducing the tip clearance have been receiving many scholars’ attention all the time, which bring turbine efficiency increasing, emissions reduction, payloads increasing, and mission range abilities extension. In order to gain the blade tip clearance dynamically, a prototype optical fiber measurement system was built and tested based on the rotor test rig. The optical fiber tip clearance measurement system consists of the reflective intensity-modulated optical fiber bundle (sensor), main signal processing unit, high-speed data acquisition card, and a computer. The static performance and dynamic performance experiments were conducted to verify the performance of the system we designed. In addition, the results show that the accuracy of the system is 25 μm or better; the stability of the measurement system was evaluated in room temperature. The clearance measurement range is about 5 mm, and sensitivity of the sensor is 0.0733/mm. Furthermore, the typical tip clearance dynamic measurement experiment results show that the system has good dynamic response characteristics as well. The system will provide a new tool for engine health monitoring or fast active tip clearance control.

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 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 of rotating instability characteristics in an axial compressor with different tip clearances

2021 ◽  
pp. 095441002199362
Author(s):  
Yadong Wu ◽  
Tao Li ◽  
Shengzhi Lai ◽  
Jie Tian ◽  
Hua Ouyang
Keyword(s):  
Flow Field ◽  
Strong Stability ◽  
Tip Clearance ◽  
Dynamic Mode Decomposition ◽  
Field Energy ◽  
Dynamic Mode ◽  
Mode Decomposition ◽  
Blade Tip ◽  
Rotating Instability ◽  
Blade Tip Clearance

It is believed that the rotating instability phenomenon originating in the compressor tip region is due to leakage flow, which is closely associated with the blade tip clearance. In this work, we have studied the correlation between the dynamic characteristics of blade tip flow and the size of tip clearance for a single-stage low-speed compressor rotor, so as to unveil the mechanism of rotating instability. The full-passage numerical simulations were carried out to obtain the variations in frequency, circumferential mode, and spatial flow field associated with rotating instability. The results of spatial mode decomposition with open clearance show the number of predominate instability modes identified are 25 and 30, respectively. By diminishing the blade tip clearance, all these unstable modes greatly diminished. The formation and propagation of the tip leakage vortex were described in detail to show the development of rotating instability. Two flow field reduced-order methods, proper orthogonal decomposition and dynamic mode decomposition, were used to analyze the flow field, energy proportion, and stability of related modes under different tip clearances. The results show that the first several modes with strong stability account for a large proportion of energy and make a major contribution to flow unsteadiness. The energy proportion and stability of rotating instability decrease as the tip clearance becomes smaller. The blade-passing frequency and its multiples emerge as the main components of the flow field.

Blade Tip Clearance Measurement Systems for High Speed Turbomachinery Applications and the Potential for Blade Tip Timing Applications

2020 ◽  
Author(s):  
Jack David Stubbs ◽  
Muhammad Arslan Shahid
Keyword(s):  
Measurement Uncertainty ◽  
High Speed ◽  
Radial Displacement ◽  
Measurement Techniques ◽  
Test System ◽  
Tip Clearance ◽  
Optical Systems ◽  
Measurement Systems ◽  
Blade Tip ◽  
Blade Tip Clearance

Abstract As turbomachinery OEMs focus efforts to further increase reliability, power and efficiencies, the running clearance between blade tips and stator continue to be of the utmost importance. This paper investigates the capability of capacitive tip clearance systems to perform individual blade tip clearance measurements on high speed rotors of up to 90,000rpm. A rotor was designed using finite element analysis; unique blade responses have been predicted. The objective of this investigation was to consider two different approaches to the application of blade tip clearance measurements and the system requirements to accurately measure low levels of radial displacement of a target rotating between 1,000rpm and 90,000rpm. The first uses the standard approach with passive probes and the second, a new technique using active probes that have demonstrated bandwidths of 1.2MHz and increased measuring range with a lower level of measurement uncertainty. Both systems’ approaches are compared, and their capabilities are evaluated for high-speed applications. The higher bandwidth capabilities of the latter system, combined with smaller sensor diameters, produces comparable signal rise times to the optical systems used in blade tip timing measurements. The difference in approach offers the potential of contamination resistant sensors for long term blade tip timing applications and measurement probes that do not require cooling systems to withstand higher temperature applications. The use of different probe configurations, in a number of applications, has demonstrated a two-fold improvement in the measurement range whilst producing lower levels of noise and uncertainty when applied to blade targets made from composites, aluminium and nickel-alloy materials. The measurement data presented includes individual blade’s radial displacement, identified shaft axial displacement, effects of resonance in the test system and the identification of the main drivers of measurement uncertainty along with an achievable value. The capacitive measurement systems’ performance for blade tip clearance is analysed and reported. The capability to perform other measurement techniques such as blade tip timing with a dual use measurement probe is also analysed and reported. This is done by correlating measurement results between the capacitive systems with that of a repeat measurement of the same target using an optical BTT system.

Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

2013 ◽  
Author(s):  
Zhaofang Liu ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Stokes Equations ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Blade Tip ◽  
Hot Streak ◽  
Blade Tip Clearance

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5% and 2.5% of the blade span with a flat tip were investigated respectively, and the uniform and non-uniform inlet temperature profiles were taken as the inlet boundary conditions. By solving the unsteady compressible Reynolds-averaged Navier-Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

scholarly journals Measuring Rotor and Blade Dynamics Using an Optical Blade Tip Sensor

1990 ◽  
Author(s):  
Harold R. Simmons ◽  
Douglas L. Michalsky ◽  
Kenneth E. Brewer ◽  
Anthony J. Smalley
Keyword(s):  
Measurement System ◽  
High Speed ◽  
High Performance ◽  
Optical Measurement ◽  
Tip Clearance ◽  
Calibration Data ◽  
Rotor Vibration ◽  
Position Sensing ◽  
Blade Tip ◽  
Blade Tip Clearance

This paper describes an optical measurement system for monitoring combustion turbine blade tips. The sensor measures distance to a blade tip using triangulation of reflected laser light. The system accomplishes triangulation using an optical position sensing device and high speed data acquisition. In this way, it is able to monitor not only average and minimum blade tip clearances, but to monitor the variations of individual blade tip clearances. By appropriate signal processing, it is possible to determine rotor vibration at the probe axial location, variations in shaft DC position, transient losses in blade tip clearance, the potential for tip and seal rubs, vibrations of individual blades in the tangential direction, and rotor torsional vibration at the probe location. Some aspects of blade and torsional vibrations would require more than one probe. The paper presents static calibration data for the measurement system, showing its degree of linearity and range. The paper also presents data obtained on a dynamic blade test rig with tip passing speeds and blade widths comparable to those encountered in high performance industrial combustion turbines. Data from this rig have been processed to show rotor vibration, shift in shaft average position, blade-to-blade tip clearance variation, and variation with speed of minimum blade tip clearance. The measurement system is designed to produce data suitable for use in the monitoring of advanced combustion turbine durability and the diagnosis of turbine functional problems, static and dynamic.

High-Speed Noncontacting Instrumentation for Jet Engine Testing

1980 ◽  
Vol 102 (4) ◽  
pp. 912-917 ◽  
Author(s):  
M. J. Scotto ◽  
M. E. Eismeier
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Tip Clearance ◽  
Jet Engines ◽  
Blade Surface ◽  
Operating Characteristics ◽  
Jet Engine ◽  
Blade Tip ◽  
Engine Testing ◽  
Blade Tip Clearance

This paper discusses high-speed, noncontacting instrumentation systems for measuring the operating characteristics of jet engines. The discussion includes optical pyrometers for measuring blade surface temperatures, capacitance clearanceometers for measuring blade tip clearance and vibration, and optoelectronic systems for measuring blade flex and torsion. In addition, engine characteristics that mandate the use of such unique instrumentation are pointed out as well as the shortcomings of conventional noncontacting devices. Experimental data taken during engine testing are presented and recommendations for future development discussed.

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