Comparative Study Between In-Situ Measured Vibration Data at Bearing and BTT on a LP Turbine Last Stage Blades in a Steam Turbo-Generator Set

2013 ◽  
Author(s):  
W. Hahn ◽  
Jyoti K. Sinha
Keyword(s):  
Vibration Measurement ◽  
Blade Vibration ◽  
Vibration Data ◽  
Turbo Generator ◽  
The Status ◽  
Blade Tip ◽  
Last Stage ◽  
Run Up ◽  
Lp Turbine

Cracking of the last stage blades of the low pressure (LP) turbines has been observed after 2007 in the 2 steam turbo-generator (TG) units out of the 4 units at the West Burton Power Plant UK. These 2 units were retrofitted with the new design LP rotor including blades in 1995 and 1997. Recent vibration measurements during machine transient and steady state operations confirms that the TG sets are running close to the machine critical speed and the blades are expected to have high vibration. Now the Unit 3 is fitted with the blade tip timing (BTT) system to monitor the LP1 last stage blades. Hence the present effort to compare the vibration of the blades by the BTT system with the bearing vibration to establish the correlation such that the status of the blade vibration can be accessed even without BTT measurement and the correlation may be used for other units with similar dynamics. The paper presents the comparison of the in-situ vibration measurement on bearings during machine run-up with online BTT data, observations, and possible correlation.

Experience With the Non-Contacting Blade Vibration Measurement Method Using Two Sensors in a Low Pressure Model Steam Turbine

2002 ◽  
Author(s):  
Zechun Hu ◽  
Gerhard Eyb ◽  
David Regnery
Keyword(s):  
Steam Turbine ◽  
Measurement System ◽  
Low Pressure ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Blade Vibration ◽  
Vibration Data ◽  
Operation Conditions ◽  
Excited Vibration ◽  
Extended Operation

This paper presents an application of a non-contacting blade tip timing measurement system using two-sensor method (so-called BSSM) at a low-pressure model steam turbine to investigate dynamic blade stress in extended operation conditions (so-called windage). An analysis method to identify the vibration frequencies and to determine the response amplitudes for the first few excited vibration mode shapes is described in detail. Objective of this paper is to discuss the performance and inherent limitations of the non-contacting measurement system. For that the BSSM results were compared with the blade vibration data obtained from strain gauges. Some experiences and suggestions are also made to improve the reliability and accuracy of this measurement system.

Vibration Investigation for Low Pressure Turbine Last Stage Blade Failure in Steam Turbines of a Power Plant

2012 ◽  
Author(s):  
Jyoti K. Sinha ◽  
W. Hahn ◽  
K. Elbhbah ◽  
G. Tasker ◽  
I. Ullah
Keyword(s):  
Power Generation ◽  
Power Plant ◽  
Steam Turbines ◽  
Cause Analysis ◽  
Low Pressure Turbine ◽  
Root Cause ◽  
Turbo Generator ◽  
Last Stage ◽  
Blade Failure

West Burton Power Plant, UK owned by EDF energy has 4 steam turbo-generator (TG) units for power generation. These units were installed and commissioned between 1967 and 1969 and have since operated smoothly without any major problems up to 2007. In 1995 and 1996, two TG sets, namely units 2 and 3, were retrofitted with the new design LP rotors and in 2005, retrofitting of HP rotor for all four TG units was commenced. The retrofitting was done without changing the foundation, but only with the aim to enhance the power output by 20MW (10 MW through LP retrofit and 10MW through HP retrofit). Cracking of the last stage blades of LP1 and LP2 turbine, steam-end blades has been observed in TG units 2 and 3 only. Hence the in-situ vibration measurements have been carried out on TG unit 3 and compared with healthy TG unit 1 to understand the dynamics of both units. This paper presents observations made on the dynamics of TG units 1 and 3, and results from the root cause analysis which may possibly lead to the solution to the blade failure problem in TG units 2 and 3.

A blade tip-timing method without once-per-revolution sensor for blade vibration measurement in gas turbine engines

2020 ◽  
Author(s):  
Chengwei Fan ◽  
Yadong Wu ◽  
Pete Russhard ◽  
Can Ruan ◽  
Anjenq Wang
Keyword(s):  
Gas Turbine ◽  
Resonance Region ◽  
Operating Conditions ◽  
Vibration Measurement ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Rotor Speed ◽  
Blade Vibration ◽  
Reference Probe ◽  
Blade Tip

The blade vibration measurement is crucial for gas turbine engines in order to ensure safe operations. One of the techniques is blade tip-timing (BTT), which is under the assumption that rotor speed is constant and depends on a once-per-revolution (OPR) timing reference to calculate the blade tip displacement, and identifying the blade sequence. However, this assumption is incorrect for transient conditions, and the installation of OPR sensor sometimes is not allowable and reliable. These reasons greatly limit the application of BTT technique. This paper proposes a self-correcting (SC) BTT method to realize the blade vibration measurement under different operating conditions without using the OPR sensor, which is based on the polynomial fitting and a reference probe is used to correct high-order fitting coefficients. Numerical results show that the SC-BTT method can greatly reduce the fitting error caused by blade pitch and vibrational parameters. Experimental results demonstrate that the proposed technique is capable of removing the limitation of the lack of OPR sensor and overcoming the drawbacks of OPR system, such as the failure of OPR sensor or low-speed resolution. For three investigated cases, the relative errors of derived rotor speed are below 0.12%. The relative error of blade peak-to-peak amplitude (PPA) and the initial phase angle are around 3% at the resonance region with engine order (EO) 2.

scholarly journals A Torsional Vibration Measurement Method for Rotating Blades Based on Blade Tip Timing

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Haonan Guo ◽  
Yongmin Yang ◽  
Fengjiao Guan ◽  
Haifeng Hu ◽  
Guoji Shen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Torsional Vibration ◽  
Measurement Method ◽  
Optimization Method ◽  
Vibration Monitoring ◽  
Vibration Measurement ◽  
Stable Operation ◽  
Blade Vibration ◽  
Blade Tip ◽  
Types Of Faults

During the working process of the turbine, some types of faults can cause changes in the vibration characteristics of the blades. The real-time vibration monitoring of the blades is of great significance to the stable operation and state-based maintenance. Torsional vibration is a kind of blade vibration modes and results in failures such as cracks easily. Thus, it is important to measure it due to the harmfulness of torsional vibration. Firstly, the principle of blade tip timing (BTT) is introduced, and the models of the blade are built to analyze the characteristics of torsional vibration. Then, the compressed sensing theory is introduced, and its related parameters are determined according to the measurement requirements. Next, based on the condition that the blade rigidity axis is not bent and bent, respectively, the layout method of sensors is proposed and the numerical simulation of the measurement process is performed. The results of the above two types of numerical simulation verify the proposed measurement method. Finally, by analyzing the influencing factors of measurement uncertainty, the optimization method of sensors’ layout is further proposed. This study can provide important theoretical guidance for the measurement of blade torsional vibration.

scholarly journals New blade tip-timing system for measuring rotor blade vibration of steam and gas turbines

2019 ◽  
Vol 137 ◽  
pp. 01040
Author(s):  
Piotr Kowaleczko ◽  
Romuald Rządkowski ◽  
Leszek Kubitz ◽  
Paweł Troka ◽  
Paweł Kowaleczko ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
Low Cost ◽  
Blade Vibration ◽  
Measurement Systems ◽  
Timing System ◽  
Blade Vibrations ◽  
Blade Tip ◽  
Run Up ◽  
Ethernet Interface

One of the crucial issues regarding turbine maintenance is registering blade vibrations. These vibrations can cause serious damage to the engine. Turbine blade vibrations were measured during nominal speed as well as during run up and run down. A new, low cost Blade Tip Timing (BTT) is presented in this paper. It composes of two main modules: the FPGA unit and PC unit. The system is based on the TerasIC DE0-CV development board controlled by the Cyclone V 5CEBA4F23C7 chip. Units communicate via an Ethernet interface. The system measures a signal for every revolution as well as up to three signals coming from independent rotor blade sensors. The PC unit records these data in .csv files. The system can be adapted to process the signals of additional sensors. The measurements of the 1st stage compressor blade vibrations in an SO-3 engine prove that the system works correctly, with no data loss during transmission between system units, and compares well with other measurement systems as well as numerical results.

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.

Vibrations of the LH2 Turbine Rotor During the Vinci Engine Test: Tip Timing Measurements and Predictions

2010 ◽  
Author(s):  
Clas Andersson ◽  
Peter Grasbon ◽  
Simon Merchant
Keyword(s):  
Test Data ◽  
Measurement System ◽  
New Technologies ◽  
Turbine Rotor ◽  
Design Tool ◽  
Vibration Measurement ◽  
Successful Implementation ◽  
Blade Vibration ◽  
Blade Tip ◽  
Large Amplitude Vibrations

A test campaign with the purpose of demonstrating new technologies introduced in the Vinci engine was performed in 2008. One of these new technologies is the blisk technology included in the LH2 fuel and LOX oxidizer pump turbines, for which Volvo Aero Corporation has the design responsibility. A challenge with blisks in rotating machinery is the risk of large amplitude vibrations due to low damping. To address the mechanical integrity of the Vinci LH2 turbine rotor blisk with respect to vibrations, an advanced blade vibration measurement system using the blade tip timing method was designed and implemented in close cooperation with the subcontractor AGILIS. The implementation of tip timing for measuring the blade vibrations of the Vinci LH2 blisk was recognized as a challenging application for this kind of measurement system. The conditions in the LH2 turbine are harsh with temperatures down to about 80 K with high pressure and hydrogen environment. Nevertheless, these challenges were systematically investigated rendering a successful implementation. The detailed analysis of the tip timing test data provided unique information for validation. More resonances than expected were confirmed. The responses, however, were modest rendering a low risk for HCF in the test. The most severe resonance in the test with respect to HCF was excited by the second stator harmonics. It was excited several times in the test campaign at about 69200 rpm. This resonance was also pointed out in the design process as being the worst one with respect to HCF. Hence, even though the test data revealed more resonances than expected, the most critical one was identified by the VAC design tool prior to the test. The agreement in predictions and test results for the critical mode was very good with respect to both frequency and response. This statement of very good agreement also applies to the frequencies associated with the other resonances in the test.

Tip-Timing Data Analysis for Mistuned Bladed Discs Assemblies

2008 ◽  
Author(s):  
Cyrille Ste´phan ◽  
Marc Berthillier ◽  
Joseph Lardie`s ◽  
Arnaud Talon
Keyword(s):  
Spectral Analysis ◽  
Optical Sensors ◽  
Fundamental Problem ◽  
Spectral Estimation ◽  
Minimum Variance ◽  
Vibration Measurement ◽  
Blade Vibration ◽  
Autocorrelation Matrix ◽  
Timing Data ◽  
Blade Tip

In turbomachine industry, bladed assembly vibration measurements are very important for blades behaviour estimation. These measurements are generally obtained from strain gauges. However, one of the most promising methods for the analysis of blade vibrations in rotating bladed assemblies is the Blade Tip Timing or Optical Blade Vibration Measurement method. A set of optical sensors is mounted on an engine casing, in front of a disc, and measures the times of arrival of each blade. These timings are then used to compute the vibrations of the blades. However the fundamental problem for spectral analysis of blade tip timing data is that the signals are undersampled and aliased. We propose here a new method for spectral estimation of blades responses from tip timing data that overcome these difficulties. The method proposed in this communication is based on the use of a minimum variance filter associated with an iterative updating of the autocorrelation matrix. That allows to process correctly a signal even if the number of known signal samples is less than equivalent Nyquist criterion. This approach is suitable for spectral analysis of undersampled and aliased signals. Perfomances of the spectral estimator have been evaluated for one simulated and one experimental test cases. The method seems very promising for the monitoring of mistuned bladed discs.

scholarly journals Status of the Ex Situ and In Situ Conservation of Brazilian Crop Wild Relatives of Rice, Potato, Sweet Potato, and Finger Millet: Filling the Gaps of Germplasm Collections

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 638
Author(s):  
Marcelo B. Medeiros ◽  
José F. M. Valls ◽  
Aluana G. Abreu ◽  
Gustavo Heiden ◽  
Suelma Ribeiro-Silva ◽  
...  
Keyword(s):  
Finger Millet ◽  
Ex Situ Conservation ◽  
Gap Analysis ◽  
In Situ Conservation ◽  
Germplasm Collection ◽  
Crop Wild Relatives ◽  
Wild Relatives ◽  
Ex Situ ◽  
The Status

This study presents the status of ex situ and in situ conservation for the crop wild relatives of rice, potato, sweet potato, and finger millet in Brazil, and the subsequent germplasm collection expeditions. This research is part of a global initiative entitled “Adapting Agriculture to Climate Change: Collecting, Protecting, and Preparing Crop Wild Relatives” supported by the Global Crop Diversity Trust. Species of the primary, secondary, and tertiary gene pools with occurrences reported in Brazil were included: Oryza alta Swallen, O. grandiglumis (Döll) Prod., O. latifolia Desv., O. glumaepatula Steud., Eleusine tristachya (Lam.) Lam., E. indica (L.) Gaertn., Solanum commersonii Dunal, S. chacoense Bitter, Ipomoea grandifolia (Dammer) O’Donell, I. ramosissima (Poir.) Choisy, I. tiliacea (Willd.) Choisy, I. triloba L., and I. cynanchifolia Meisn. The status of the ex situ and in situ conservation of each taxon was assessed using the gap analysis methodology, and the results were used to plan 16 germplasm collection expeditions. Seeds of the collected material were evaluated for viability, and the protocols for seed germination and cryopreservation were tested. The final conservation score, resulting from the gap analysis and including the average of the ex situ and in situ scores, resulted in a classification of medium priority of conservation for all the species, with the exception of I. grandifolia (high priority). The total accessions collected (174) almost doubled the total accessions of these crop wild relatives incorporated in Embrapa’s ex situ conservation system prior to 2015. In addition, accessions for practically absent species were collected for the ex situ conservation system, such as Ipomoea species, Eleusine indica, and Solanum chacoense. The methods used for dormancy breaking and low temperature conservation for the Oryza, Eleusine, and Ipomoea species were promising for the incorporation of accessions in the respective gene banks. The results show the importance of efforts to collect and conserve ex situ crop wild relatives in Brazil based on previous gap analysis. The complementarity with the in situ strategy also appears to be very promising in the country.

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