Vibration Measurements on Rotating Machinery Using Laser Doppler Velocimetry

1994 ◽  
Vol 116 (3) ◽  
pp. 326-331 ◽  
Author(s):  
S. J. Rothberg ◽  
N. A. Halliwell
Keyword(s):  
Velocity Component ◽  
Laser Doppler Velocimetry ◽  
Rotating Machinery ◽  
Vibration Measurement ◽  
Surface Velocity ◽  
Laser Vibrometer ◽  
Doppler Velocimetry ◽  
Laser Vibrometry ◽  
Vibration Measurements ◽  
Measurement Direction

This paper explores the use of laser vibrometry for vibration measurement directly from a rotating component. The presence of a surface velocity component due to the rotation itself is shown to create a strong measurement dependency on vibration perpendicular to the intended measurement direction. Particular ambiguity results at synchronous frequencies. A mathematical means to resolve the genuine vibration components from two simultaneous laser vibrometer measurements is presented and shown to be effective in the study of nonsynchronous rotor vibrations.

Velocity Fluctuations at the Walls of a Packed Bed of Spheres for Medium Re-Numbers

1987 ◽  
Vol 109 (3) ◽  
pp. 242-247 ◽  
Author(s):  
R. H. Bahnen ◽  
C. G. Stojanoff
Keyword(s):  
Velocity Component ◽  
Laser Doppler Velocimetry ◽  
Convex Surface ◽  
Packed Bed ◽  
Experimental Results ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Cylindrical Container ◽  
Velocity Fluctuations ◽  
Different Diameters

A packed bed which is uniformly filled with equally large spheres is subjected to transpiration flow. The velocity component perpendicular to its surface was measured by means of Laser-Doppler-Velocimetry. Special attention is paid to the velocity fluctuations occurring at the wall of the cylindrical container and at the convex surface of rods of different diameters inserted in the bed center. The Re-numbers were between 800 and 1500. The experimental results are compared with results obtained from the literature.

Redesign of Ultrasonic Block Horns for Improved Vibration Performance

1997 ◽  
Vol 119 (3) ◽  
pp. 410-414 ◽  
Author(s):  
M. Lucas ◽  
A. C. Smith
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Laser Doppler Velocimetry ◽  
Speckle Pattern ◽  
Measurement Techniques ◽  
Theoretical Data ◽  
Vibration Measurement ◽  
Electronic Speckle Pattern Interferometry ◽  
Doppler Velocimetry ◽  
Vibration Performance

Ultrasonic block horns are prone to reliability problems associated with modal activity close to the tuned operating frequency. This paper presents an approach to block horn design, which relies on two laser based vibration measurement techniques, electronic speckle pattern interferometry (ESPI) and laser doppler velocimetry (LDV) modal analysis, to validate finite element (FE) models. Block horn vibration characteristics are interpreted from experimental and theoretical data such that successful horn redesign can be achieved from modifications to the FE models.

Application of Laser Vibrometry to Vibration Measurement on Rotating Components

1995 ◽  
Author(s):  
Steven J. Rothberg ◽  
Neil A. Halliwell
Keyword(s):  
Vibration Analysis ◽  
Laser Speckle ◽  
Vibration Measurement ◽  
Torsional Vibrations ◽  
Radial Vibration ◽  
Laser Vibrometry ◽  
Laser Doppler Vibrometry ◽  
Vibration Measurements ◽  
Speed Fluctuations ◽  
Fundamental Limitation

Abstract This paper describes the application of Laser Doppler Vibrometry to vibration measurements on rotating targets. The noise generating mechanism of the laser speckle phenomenon is first explained before confirmation of the insensitivity of measurements to target shape. The principal focus of the paper is on the fundamental limitation associated with the use of Laser Vibrometers for radial vibration measurements directly on rotating components. In such measurements significant cross-sensitivities to speed fluctuations, including torsional vibrations, and in-plane vibrations are evident, preventing synchronous vibration analysis. Mathematical and electronic means to resolve the correct orthogonal vibration components are presented and shown to be successful in enabling the use of Laser Vibrometry for non-synchronous vibration measurements.

scholarly journals Laser doppler velocimetry and confined flows

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 825-836
Author(s):  
Jelena Ilic ◽  
Slavica Ristic ◽  
Milesa Sreckovic
Keyword(s):  
Velocity Component ◽  
Laser Doppler Velocimetry ◽  
Focal Length ◽  
Cylindrical Tube ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Focal Length Lens ◽  
Cylindrical Tubes ◽  
Set Up ◽  
Confined Flows

Finding the mode, in which two component laser Doppler velocimetry can be applied to flows confined in cylindrical tubes or vessels, was the aim of this study. We have identified principle issues that influence the propagation of laser beams in laser Doppler velocimetry system, applied to flow confined in cylindrical tube. Among them, the most important are influences of fluid and wall refractive indices, wall thickness and internal radius ratio and beam intersection angle. In analysis of the degrees of these influences, we have applied mathematical model, based on geometrical optics. The separation of measurement volumes, that measure different velocity components, has been recognized as the main drawback. To overcome this, we propose a lens with dual focal length ? primary focal length for the measurement of one velocity component and secondary focal length for the measurement of the other velocity component. We present here the procedure for calculating the optimal value of secondary focal length, depending on experimental set-up parameters. The mathematical simulation of the application of the dual focal length lens, for chosen cases presented here, confirmed the accuracy of the proposed procedure.

scholarly journals Application of Laser Vibrometry to Assess Defects in Ship Hull’s Welded Joints’ Technical Condition

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 895
Author(s):  
Adam Szeleziński ◽  
Adam Muc ◽  
Lech Murawski ◽  
Marcin Kluczyk ◽  
Tomasz Muchowski
Keyword(s):  
Optical Sensors ◽  
Welded Joints ◽  
Measurement Data ◽  
Technical Condition ◽  
Laser Vibrometer ◽  
Laser Vibrometry ◽  
Destructive Testing ◽  
Laser Sensors ◽  
Measurement Methodology ◽  
The Mathematical Model

The paper presents the measurement process and test results for six thin-walled plates with different dynamic characteristics caused by different defects of welded joints. The tests were carried out using non-destructive testing (NDT). The authors made an attempt to determine the validity of the use and degree of effectiveness of the tests based on laser vibrometry in detecting defects in welded joints. The tests of welded plates were carried out using displacement laser sensors and piezoelectric accelerometers, while the source of vibration extortion was a modal hammer. In the adopted measurement methodology, the application of accelerometers was to obtain the reference data, which allowed for comparison with the measurement data obtained from the laser vibrometer. The analysis of the obtained measurement data, in the fields of time and frequency, made it possible to verify the correctness of the data obtained by means of laser vibrometry and to determine the requirements which are necessary for the correct performance of NDT tests and in the future structural health monitoring (SHM) system of welded joints with the use of a laser vibrometer. The mathematical model developed in the MSC software Pastran-Nastran was also used in the work. The model was developed for the purpose of mutual verification of the measurement and calculation tests. At the present stage of work, it can be stated that the results obtained by laser vibrometry methods should be treated as a supplement to the research conducted with traditional piezoelectric accelerometers. In certain situations, they can be used as an alternative to accelerometers, due to the fact that laser sensors do not require direct contact with the examined object. Where the object under test may be in a strong electromagnetic field, optical sensors are better suited than contact sensors.

scholarly journals Fiber Bragg Grating Sensors for Underwater Vibration Measurement: Potential Hydropower Applications

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4272
Author(s):  
Oscar de la Torre ◽  
Ignazio Floris ◽  
Salvador Sales ◽  
Xavier Escaler
Keyword(s):  
Fiber Bragg Grating ◽  
Numerical Models ◽  
Vibration Measurement ◽  
Quality Data ◽  
Bragg Grating ◽  
Laser Vibrometer ◽  
Main Concern ◽  
High Expectations ◽  
Fiber Bragg Grating Sensors ◽  
Hydraulic Machinery

The present paper assesses the performance and characteristics of fiber Bragg grating sensors, with a special interest in their applications in hydraulic machinery and systems. The hydropower industry is turning to this technology with high expectations of obtaining high quality data to validate and calibrate numerical models that could be used as digital twins of key assets, further strengthening the sector’s relevant position within industry 4.0. Prior to any validation, fiber Bragg grating sensors’ ability to perform well underwater for long periods of time with minimal degradation, and their ease of scalability, drew the authors´ attention. A simplified modal analysis of a partially submerged beam is proposed here as a first step to validate the potential of this type of technology for hydropower applications. Fiber Bragg grating sensors are used to obtain the beam’s natural frequencies and to damp vibrations under different conditions. The results are compared with more established waterproof electric strain gauges and a laser vibrometer with good agreement. The presence of several sensors in a single fiber ensures high spatial resolution, fundamental to precisely determine vibration patterns, which is a main concern in this industry. In this work, the beam’s vibration patterns have been successfully captured under different excitations and conditions.

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