Film thickness and wave velocity measurement using reflected laser intensity

Oliveira, Fábio Santos de; Yanagihara, Jurandir Itizo; Pacifico, Antonio Luiz

doi:10.1590/s1678-58782006000100003

Cited by 15 publications

(7 citation statements)

References 9 publications

(10 reference statements)

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“…In addition to this Oliveira et al (2006) used the technique with fibre-optic cables with receiving sensors set 3mm apart to measure the film of liquid in a trough. They first created a theoretical model of reflected light intensity predicting that films less than 500 µm thick could be measured; however they decided to run the experiment to measure films down to 1.5 mm which accurately matched the model, as well as concentrating on trying to measure thicker films up to 4mm; overall using photons with wavelengths in the visible spectrum as a film measurement technique can be very accurate and allow for measurement of films less than 100 nm (Oliveira et al 2006).…”

Section: Photonsmentioning

confidence: 99%

Wet steam measurement techniques

Walker

Barham²,

Giddings

et al. 2018

Reviews in Chemical Engineering

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Abstract In recent years a greater need for power station efficiency has become evident; improving turbine blade efficiency is one of the methods proposed. This efficiency depends upon the wetness of the steam that comes into contact with the blades of the low-pressure turbine stage in general and all turbines in nuclear power generation. Therefore, measurement of the moisture content of the steam in real time in conjunction with an accurate measure of steam velocity can give an overall mass flow re-entering the turbine, allowing for a feedback control. The system can rely on one technique that can measure suspended droplets and wall-bound liquid film, or a combination of techniques can operate together. This work gives a comprehensive review of the different techniques used to measure the moisture content including the liquid film and moisture content and techniques that can give measurements on both simultaneously. Each technique has its strengths and weaknesses, and they were analysed to see which technique works best overall and which techniques can be used together.

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Section: Photonsmentioning

confidence: 99%

Wet steam measurement techniques

Walker

Barham²,

Giddings

et al. 2018

Reviews in Chemical Engineering

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“…This temporal-to-spatial operation is developed based on Taylor's frozen flow hypothesis [41], which stated that if the turbulence intensity is small compared to the mean flow velocity, the temporal response at a fixed point in space can be regarded as the result of an unchanging spatial pattern convecting uniformly past the point at the mean flow velocity [42]. Taylor's hypothesis assumes that the time-space transformation is linear: , , 0 R r R r U (10) which can be further transformed to relate the time-correlation and space-correlation: 0, , 0 R R U (11) Therefore, the spatial distribution can be constructed simply using Eq. (12).…”

Section: Spatial Expansion Of Temporal Thickness Fluctuationmentioning

confidence: 99%

“…Over the years, various experimental techniques have been developed to measure thin liquid film flows [10][11][12][13][14][15][16]. Among these techniques, fluorescence imaging based, stereoscopic imaging based, density based, and structured light projection techniques are most frequently used.…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of wave features in wind-driven water film flow using ultrasonic pulse-echo technique

Liu¹,

Bond²,

Hu³

2016

AIP Conference Proceedings

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“…The temporal resolution for measuring the liquid film is determined by the bandwidth of the photoelectric sensor of sampling rate of voltage recorder that records the light intensity. Further improvements to this approach have enabled measurement of relatively thick liquid films (up to several millimeters thick) and their wave velocities via increasing the number of fibers or expanding the fiber diameter (Oliveira, 2006). However, the measurement resolution decreases as the film thickness reduces because the light emitted from the fiber has a Gaussian distribution as discussed in the present paper; this distribution is characteristic of the widely used optical fiber (the graded index (GI)-type fiber), designed mainly for long-distance communications.…”

Section: Introductionmentioning

confidence: 99%

Accurate thin-film measurement method based on a distribution of laser intensity emitted from optical fiber: Proposal of step light emitted model for ray-tracing simulation

Yamaguchi

Sanada

Mizushima

2020

Mechanical Engineering Letters

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The accurate measurement of thin liquid films in various environments is essential for several industrial applications. In this regard, measurement procedures involving the use of optical fibers are preferred because such fibers are resistant to heat and pressure. Herein, we propose a high-accuracy method to measure liquid films with thicknesses of <100 μm (about fiber diameter) on the basis of the variation in the intensity distribution of the laser light emitted from the optical fiber; the thickness is measured by using the light reflected from the airliquid interface (called the glare light in this study). First, instead of using light with a Gaussian distribution (characteristic of conventional graded-index fibers), we consider a stepped-index-type optical fiber with a step distribution. We model the distribution of the light emitted from the optical fiber and analyze the reflected light, i.e., glare light, via the ray-tracing method. We model three distributions: the Gaussian, point-like, and step distributions, and then we found that the step-distribution-based approach facilitates high-resolution measurements of liquid films with thicknesses less than optical fiber diameter. Moreover, the reflected light intensities for different film thicknesses closely agreed with the experimental results obtained using a steppedindex fiber. Remarkably, the intensity of the reflected light linearly decreases with the increase in the film thickness when using the step distribution. The numerical results quantitatively agreed with experiments; therefore, these results indicate the possibility of numerical calibration for liquid-film measurements with the use of the proposed step distribution model.

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Film thickness and wave velocity measurement using reflected laser intensity

Cited by 15 publications

References 9 publications

Wet steam measurement techniques

Wet steam measurement techniques

Reconstruction of wave features in wind-driven water film flow using ultrasonic pulse-echo technique

Accurate thin-film measurement method based on a distribution of laser intensity emitted from optical fiber: Proposal of step light emitted model for ray-tracing simulation

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