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.

scholarly journals Vibration Measurement of Rotating Blades Using a Root Embedded PZT Sensor

2008 ◽  
Vol 15 (5) ◽  
pp. 517-541 ◽  
Author(s):  
M. Sunar ◽  
B.O. Al-Bedoor
Keyword(s):  
Finite Element ◽  
Experimental Studies ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Rotating System ◽  
Blade Vibration ◽  
Wide Range ◽  
Finite Element Package ◽  
Steady State Responses ◽  
State Responses

Finite element and experimental studies are carried out to test the suitability of a piezoelectric (PZT) sensor in measuring vibrations of blades modeled as beams. The rotating system contains twelve blades mounted to the shaft through a rotor. The PZT sensor is secured in the root between the rotor and blade. First, finite element results are obtained using the finite element package ANSYS. A modal analysis is performed on the system to identify modes and mode shapes. Transient, harmonic and steady-state responses are then computed to test the ability of the PZT sensor in generating signals for blade vibrations. For the experimental part, the blade vibration signals are produced using the PZT sensor and a strain-gage, and the outputs are compared with each other. From both the finite element and experimental results, it is concluded that the root-embedded PZT sensor can be effectively used for blade vibration measurements in a wide range of cases.

Measurement and Analysis of Shipboard Vibrations

1998 ◽  
Vol 35 (01) ◽  
pp. 1-9
Author(s):  
DeBord Frank ◽  
Hennessy William ◽  
McDonald Joseph
Keyword(s):  
Measurement System ◽  
Vibration Response ◽  
Vibration Measurement ◽  
Ship Construction ◽  
Vibration Data ◽  
Construction Specifications ◽  
Analysis Methods ◽  
Measurement And Analysis ◽  
Potential Problems ◽  
Maintenance Requirements

Excessive shipboard vibrations can cause structural and machinery failures, crew discomfort and fatigue, and increased maintenance requirements for shipboard systems. In many cases ship construction specifications require the shipyard to demonstrate "acceptable " levels of vibration using measurements completed during sea trials. This paper provides an overview of standards for these measurements and modern techniques used to collect and analyze the specified vibration data. A brief discussion of the types of vibrations found on ships and their causes is followed by a review of codes, guides and standards for vibration measurement. Instrumentation suitable for measurement of each type of vibration response is described and the design of a typical trial measurement system is presented. Techniques for analyzing and presenting trial results are reviewed and compared with analysis methods specified by SNAME, ISO and NAVSEA. Finally, a discussion of potential problems faced by an owner and shipyard in developing and meeting a vibration measurement specification is offered.

Damping Identification and its Comparison for Various Types of Blade Couplings

2013 ◽  
Author(s):  
Zdenek Kubin ◽  
Vaclav Polreich ◽  
Vaclav Cerny ◽  
Petra Babkova ◽  
Lubos Prchlik
Keyword(s):  
Steam Turbine ◽  
Damping Ratio ◽  
Nonlinear Behavior ◽  
Mode Shapes ◽  
Material Damping ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Linear Behavior ◽  
Disc Rotation ◽  
Identification Technique

Regarding steam turbine blade vibrations, damping of blade as well as bladed disc mode shapes is one of the most important parameters in terms of steam turbine operation. A value of the parameter depends on properties of material used for manufacturing and construction elements of the blades and the discs such as blade roots, shrouds, tiebosses (snubbers) and dampers. This article deals with a comparison of damping of mode shapes for particular blade couplings and shows which methods are suitable for determination of the damping in individual cases. The whole identification procedure of the damping together with its specifics is also presented. At first, an identification technique of material damping ratio is introduced and its results are given for different materials. The material damping ratio is assessed as material strain dependent. Subsequently, damping ratio of bladed disc mode shapes under bladed disc rotation is identified taking into account two alternatives. The alternatives differ in such a way that blades have been free for the first time and then coupled with friction dampers. Outcomes presented in the article illustrate good agreement between damping ratio of bladed disc mode shapes with free blades and material used for manufacturing of the blades. On the other hand, damping ratio of bladed disc mode shapes with friction dampers is significantly different and strongly dependent on blade vibration amplitudes as well as nodal diameters of bladed disc mode shapes. Finally, nonlinear behavior of the bladed disc has been revealed along large blade vibration amplitudes and higher nodal diameters of the disc. The non-linear behavior manifests itself in such a way that values of natural frequencies of the disc have become dependent on blade vibration amplitudes.

Analyses of Temperature Distribution on Steam Turbine Last Stage Low Pressure Buckets at Low Flow Operations

2011 ◽  
Author(s):  
Victor Filippenko ◽  
Boris Frolov ◽  
Andrey Chernobrovkin ◽  
Bin Zhou ◽  
Amir Mujezinovic´ ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Fluid Dynamic ◽  
Low Pressure ◽  
Low Flow ◽  
Experimental Investigations ◽  
Temperature Prediction ◽  
Operation Conditions ◽  
Wide Range ◽  
Last Stage ◽  
Lp Turbine

Steam turbine power plant operations during start up and during operation at high exhaust pressure have the potential to result in an extremely low steam flow through the Low Pressure (LP) turbine. This inevitably leads to windage and results in significant temperature increases in the Last Stage Buckets (LSBs). High steam temperature can also initiate potential thermo-mechanical failure of the LSBs. Temperature prediction for a wide range of operational regimes imposes a significant challenge to modern LSB design. Extensive numerical and experimental investigations on an LP section steam turbine with LSBs of different lengths at typical low flow operation conditions have been conducted with the primary focus on LSB temperature prediction. A Low Pressure Development Turbine (LPDT) test rig was used to help develop and validate Computational Fluid Dynamic (CFD) based temperature prediction methodologies, which later were applied to predict operational temperatures for multiple LP section configurations under development. This article presents some important results of LPDT test measurements as well as CFD predictions of LP turbine flow structures and temperature distributions in last stage buckets.

Some Remarks on the Dynamic Behaviour of Integrally Shrouded Blade Rows

2011 ◽  
Author(s):  
N. Bachschmid ◽  
S. Bistolfi ◽  
S. Chatterton ◽  
M. Ferrante ◽  
E. Pesatori
Keyword(s):  
Steam Turbine ◽  
Natural Frequencies ◽  
Low Pressure ◽  
Contact Forces ◽  
Mode Shapes ◽  
Torsional Vibrations ◽  
Vibration Modes ◽  
Nodal Diameter ◽  
Blade Row ◽  
Pressure Steam

Actual trend in steam turbine design is to use blades with integral shrouds, for high pressure and intermediate pressure steam turbine sections, as well as also for the long blades of the low pressure sections. The blades are inserted with their root into the seat on the shaft in such a way that the blades are slightly forced against each other in correspondence of the shrouds. In long blades of low pressure stages the forcing can be obtained by the untwisting of twisted blades due to the effect of the huge centrifugal forces. The dynamic behavior of these blade rows is difficult to predict due to the nonlinear effect of the contact forces and due to friction. Different models for the contact are proposed and compared. The resulting natural frequencies of the blade row as a function of the different nodal diameter mode shapes are highly depending on the assumed models. For avoiding resonant conditions with engine order excitations, the natural frequencies must be calculated with good accuracy. Some of the modes of the blade row, typically for the last stage of the low pressure steam turbine, can couple with some vibration modes of the rotor: flexural vibrations of the shaft couple with 1 nodal diameter mode shape of the row in axial direction and torsional vibrations of the shaft couple with the 0 nodal diameter mode in tangential direction. Therefore analyses of lateral and torsional vibrations of low pressure steam turbine shafts require also an accurate analysis of the blade row vibration modes.

Blade Vibration Monitoring in a Low-Pressure Steam Turbine

2018 ◽  
Author(s):  
Radosław Przysowa
Keyword(s):  
Embedded System ◽  
Steam Turbine ◽  
Turbine Blades ◽  
Low Pressure ◽  
Vibration Monitoring ◽  
Blade Vibration ◽  
Collaborative Project ◽  
Pressure Steam ◽  
The Embedded System ◽  
Start Ups

A tip-timing system is used in a coal power station to investigate and mitigate excessive blade vibrations in the exit stage of the low-pressure steam turbine. There are presented hardware and software solutions used to monitor blade responses as well as the analyses of amplitude and frequency trends observed during the 5-year collaborative project, including operation at the nominal speed and during the shutdowns and start-ups. The transition from data acquisition to the embedded system with the partial reuse of tip-timing algorithms and LabView code is demonstrated. The proposed system processes the data coming from the turbine blades in real time and operates autonomously or under the supervision of the PC-based client program connected to the network. Acquired data are stored in a cyclic buffer and can be transferred to the host. The stack pattern is used to distinguish blades and calculate rotating reference. Tip deflection is analysed statistically and evaluated against defined reference patterns.

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.

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