Fiber Bragg grating sensor for two-phase flow in microchannels

Abstract

A new non-intrusive measurement technique for two-phase flow in microchannels is presented. The development of an evanescent field-based optical fiber Bragg grating (FBG) sensor is described, and experiments coupled with flow visualization demonstrating the performance of this sensor are presented. Two adjacent 1-mm FBGs in etched D-shaped fiber are embedded into the surface of a PDMS microchannel. Experiments are conducted in both droplet and slug flow regimes and highspeed digital video is captured synchronously with the sensor data. The FBGs exhibit an on-off type response to the passage droplets which is shown to correlate precisely with the passage of the liquid phase. This correlation enables the measurement of droplet average velocity and size using only the sensor data. In addition to the use of both FBG signals for the purpose of measuring droplet speed and size, it is shown that for droplets larger than the FBG length, a single FBG can be used to estimate the convection velocity and size of fast moving droplets. This sensing method is potentially useful for monitoring twophase flow in fuel cells and microfluidic applications such as micro-heat exchangers and lab-on-a-chip systems.

Detection of petrol adulteration using TiO2-coated etched clad based FBG sensor

“…This affects the FBGs' net effective index because of the RI of the surrounding medium. For conditions of constant temperature and strain, a slight change in the Bragg wavelength caused by a change in the effective RI can be stated by [22],…”

Recent advances in optical fiber devices for microfluidics integration

“…David et al described an optical fiber sensor format embedded into a microchannel for measuring the size and velocity of droplets in a two phase microflow situation using a “D‐shaped” fiber Bragg grating (FBG), where the cladding has been thinned on one side of the fiber so that the evanescent field can be accessed. The average difference in velocity estimations using the fiber sensor and a traditional imaging technique was estimated to be 11.6% and was dependent upon the accuracy of the periodicity and lengths of the FBGs.…”

Interfacial Phenomena and Heat Transfer in Proton Exchange Membrane Fuel Cells

“…These experiments applied a simplified model to mimic the phenomena during an actual fuel cell operation process. Droplets (Ha et al, 2008;Lee et al, 2010;Colosqui et al, 2011;Venkatramana et al, 2009;Han et al, 2012b;David et al, 2012), together with slug, film, and mist flow patterns (Lu et al, 2009;Grimm et al, 2012;Wu and Djilali, 2012), can be obtained through ex situ experiments. Other patterns like annulus (Adroher and Wang, 2011) or intermittent and chaos flow (Chen, 2010), which are not the principal patterns in an operating PEMFC, can also be obtained through ex situ experiments.…”