scholarly journals Reconstructed Order Analysis-Based Vibration Monitoring under Variable Rotation Speed by Using Multiple Blade Tip-Timing Sensors

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3235 ◽  
Author(s):  
Zhongsheng Chen ◽  
Jianhua Liu ◽  
Chi Zhan ◽  
Jing He ◽  
Weimin Wang
Keyword(s):  
High Speed ◽  
Rotation Speed ◽  
Reconstruction Algorithm ◽  
Vibration Monitoring ◽  
Reconstruction Algorithms ◽  
Monitoring Method ◽  
Vibration Signals ◽  
Order Analysis ◽  
Blade Tip ◽  
Sensor Configuration

On-line vibration monitoring is significant for high-speed rotating blades, and blade tip-timing (BTT) is generally regarded as a promising solution. BTT methods must assume that rotating speeds are constant. This assumption is impractical, and blade damages are always formed and accumulated during variable operational conditions. Thus, how to carry out BTT vibration monitoring under variable rotation speed (VRS) is a big challenge. Angular sampling-based order analyses have been widely used for vibration signals in rotating machinery with variable speeds. However, BTT vibration signals are well under-sampled, and Shannon’s sampling theorem is not satisfied so that existing order analysis methods will not work well. To overcome this problem, a reconstructed order analysis-based BTT vibration monitoring method is proposed in this paper. First, the effects of VRS on BTT vibration monitoring are analyzed, and the basic structure of angular sampling-based BTT vibration monitoring under VRS is presented. Then a band-pass sampling-based engine order (EO) reconstruction algorithm is proposed for uniform BTT sensor configuration so that few BTT sensors can be used to extract high EOs. In addition, a periodically non-uniform sampling-based EO reconstruction algorithm is proposed for non-uniform BTT sensor configuration. Next, numerical simulations are done to validate the two reconstruction algorithms. In the end, an experimental set-up is built. Both uniform and non-uniform BTT vibration signals are collected, and reconstructed order analysis are carried out. Simulation and experimental results testify that the proposed algorithms can accurately capture characteristic high EOs of synchronous and asynchronous vibrations under VRS by using few BTT sensors. The significance of this paper is to overcome the limitation of conventional BTT methods of dealing with variable blade rotating speeds.

scholarly journals Compressed Sensing-Based Order Analysis for Blade Tip Timing Signals Measured at Varying Rotational Speed

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Suiyu Chen ◽  
Yongmin Yang ◽  
Haifeng Hu ◽  
Fengjiao Guan ◽  
Guoji Shen ◽  
...  
Keyword(s):  
Compressed Sensing ◽  
Rotational Speed ◽  
High Speed ◽  
Blade Vibration ◽  
Vibration Signals ◽  
Order Analysis ◽  
Sensor Arrangement ◽  
Bandwidth Limitation ◽  
Blade Tip ◽  
The Mathematical Model

Monitoring the vibrations of high-speed rotating blades is significant to the security of turbomachineries. Blade tip timing (BTT) is considered as a promising technique for detecting blade vibrations without contact online. However, extracting blade vibration characteristics accurately from undersampled BTT signals measured at varying rotational speed (VRS) has become a big challenge. The existing two methods for this issue are restricted within the order bandwidth limitation and require prior information and precise sensor installation angles, which is often unpractical. To overcome these difficulties, a compressed sensing-based order analysis (CSOA) method was proposed. Its feasibility comes from the sparsity of BTT vibration signals in the order domain. The mathematical model for the proposed method was built, and the optimizing principles for sensor number and sensor arrangement were given. Simulated and experimental results verified the feasibility and advantages of the proposed method that it could extract order spectrum accurately from BTT vibration signals measured at VRS without the drawbacks in the existing two methods.

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

2018 ◽  
Vol 18 (6) ◽  
pp. 243-250 ◽  
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.

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

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.

Blade tip timing vibration monitoring method based on fiber Bragg

2013 ◽  
Author(s):  
Fei Wu ◽  
Lei Liang ◽  
Junya Xing ◽  
Lin Wang ◽  
Lang Jia
Keyword(s):  
Vibration Monitoring ◽  
Monitoring Method ◽  
Blade Tip

scholarly journals Undersampled Blade Tip-Timing Vibration Reconstruction under Rotating Speed Fluctuation: Uniform and Nonuniform Sensor Configurations

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Zhongsheng Chen ◽  
Jing He ◽  
Chi Zhan
Keyword(s):  
Signal Reconstruction ◽  
Reconstruction Error ◽  
Reconstruction Method ◽  
Reconstruction Algorithms ◽  
Rotating Speed ◽  
Rotating Blade ◽  
Reconstruction Methods ◽  
Speed Fluctuation ◽  
Blade Tip ◽  
Sensor Configuration

Blade tip-timing (BTT) is a promising method of online monitoring rotating blade vibrations. Since BTT-based vibration signals are typically undersampled, how to reconstruct characteristic vibrations from BTT signals is a big challenge. Existing reconstruction methods are mainly based on the assumption of constant rotation speeds. However, rotating speed fluctuation is inevitable in many engineering applications. In this case, the BTT sampling process should be nonuniform, which will cause existing reconstruction methods to be unavailable. In order to solve this problem, this paper proposes a new reconstruction method based on nonlinear time transformation (NTT). Firstly, the effects of rotating speed fluctuation on BTT vibration reconstruction are analyzed. Next, the NTT of BTT sampling times under rotating speed fluctuation is presented. Then, two NTT-based reconstruction algorithms are derived for uniform and nonuniform BTT sensor configurations, respectively. Also several evaluation metrics of BTT vibration reconstruction under rotating speed fluctuation are defined. Finally, numerical simulations are done to verify the proposed algorithms. The results testify that the proposed NTT-based reconstruction method can reduce effectively the influence of rotating speed fluctuation and decrease the reconstruction error. In addition, rotating speed fluctuation has more bad effects on the reconstruction method under nonuniform sensor configuration than under uniform sensor configuration. For nonuniform BTT signal reconstruction under rotating speed fluctuation, more attentions should be paid on selecting proper angles between BTT sensors. In summary, the proposed method will benefit for detecting early blade damages by reducing frequency aliasing.

scholarly journals Blade tip timing vibration monitoring method based on fiber Bragg grating

2014 ◽  
Vol 4 (2) ◽  
pp. 188-192 ◽  
Author(s):  
Fei Wu ◽  
Lei Liang ◽  
Junya Xing ◽  
Lin Wang ◽  
Lang Jia
Keyword(s):  
Fiber Bragg Grating ◽  
Vibration Monitoring ◽  
Bragg Grating ◽  
Monitoring Method ◽  
Blade Tip

Blade damage prognosis based on kernel principal component analysis and grey model using subsampled tip-timing signals

2014 ◽  
Vol 228 (17) ◽  
pp. 3178-3185 ◽  
Author(s):  
Chen Zhongsheng ◽  
Yang Yongmin ◽  
Guo Bin ◽  
Hu Zheng
Keyword(s):  
Principal Component Analysis ◽  
High Speed ◽  
Damage Index ◽  
Principal Component ◽  
Component Analysis ◽  
Vibration Monitoring ◽  
Grey Model ◽  
Kernel Principal Component Analysis ◽  
Damage Prognosis ◽  
Blade Tip

Damage prognosis of high-speed blades is very important for industrial turbomachinery. Nowadays, vibration monitoring using blade tip-timing methods is becoming promising. However, its main drawback is blade tip-timing signals are subsampled. Very few works have been done on damage prognosis using subsampled blade tip-timing signals. This paper investigates a novel method of blade damage prognosis based on kernel principal component analysis and grey model. Firstly, a nonaliasing reconstruction algorithm of subsampled blade tip-timing signals is proposed based on the Shannon theorem and wavelet packet transform. Secondly, kernel principal component analysis is done on the damage feature space and a damage index is defined by Mahalanobis distance. Then a grey model (1) model is proposed for damage prognosis. In the end, an experimental setup is built and a long time testing is done for collecting samples. The experimental results validate the superiority of the proposed method.

Reconstruction of Three-Dimensional Gas Metal Arc Weld Pool Surface From Reflected Laser Pattern

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
XiaoJi Ma ◽  
YuMing Zhang
Keyword(s):  
Weld Pool ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Three Dimensional ◽  
Reconstruction Algorithm ◽  
Reconstruction Algorithms ◽  
Surface Geometry ◽  
Pool Surface ◽  
Metal Arc Welding ◽  
Weld Pool Surface

A system has been developed to measure the three-dimensional weld pool surface geometry in the gas metal arc welding (GMAW) process. It utilizes the specular nature of the weld pool surface by projecting a five-line laser pattern onto the surface and imaging its reflection. Specifically, the laser reflection is intercepted by an imaging plane and captured using a high speed camera. The reflected pattern is used to reconstruct the weld pool surface based on the law of reflection. Two reconstruction algorithms, referred to as center-points reconstruction and piece-wise weld pool surface reconstruction algorithm, are applied to sequentially reconstruct the weld pool height and three-dimensional surface geometry. Reconstructions has been conducted using simulated weld pool surface to provide a method to compare the reconstruction result with a known surface and evaluate the reconstruction accuracy. It is found that the proposed method is capable of reconstructing weld pool surface with acceptable accuracy. The height error of reconstructed center-points is less than 0.1 mm and the error of estimated weld pool boundary is less than 10%. Reconstruction results from images captured in welding experiments are also demonstrated.

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