The study and measurement of two-phase flow is very important in industry, since the components, contents and distributions of the flow have great influence on the produce involving its quality, cost and even safety. Many methods have been perused including electrical capacitance tomography (ECT), electrical impedance tomography (EIT) and ultrasonic computed tomography (UCT), while optical fiber process tomography (OFPT) is a new one, which owns all the advantages of the optical fiber sensors, such as small, safety, free of electromagnetic interference and having high sensitivity in the measurement of low-density transparent media. In this paper, a practical optical fiber process tomography system is developed, which can be used in the industry filed to measure the medium distributions and contents. The liquid-solid samples are measured and reconstructed and the results show that positions of the solid objects are reoccurred exactly. The crude oil with opaque performance can be regarded as the solid, so that the oil-water two-phase flow can be measured the same as liquid-solid two-phase flows by the new OFPT system. The relative reconstructed resolution is 1.67 from experimental results.
KEYWORDS: Optical fibers, Optical tomography, Fiber optics sensors, Tomography, Signal attenuation, Signal processing, Process control, Sensors, GRIN lenses, Computing systems
The measurement of the concentration distribution is always important in industry. Many researches on image reconstruction of the two phase-flow field have been made in recent years. Various methods have been used such as capacity CT, resistance CT, x-ray CT and so on. When the flow has low concentration, however, measurement accuracy of these methods is poor. In addition, it needs the measurement to be free of charge in some case. In this paper, we have a pilot study for the two-phase flow utilizing the optical fiber sensors. Two turbidity samples with different attenuation have been used to simulate the cross section distribution of the two-component flow. The graded-index fiber lens in the end of the optical fiber has been used in order to improve the coupling efficient and decrease the cross talk of the adjacent channel s. Finally, we make use of the linear back projection arithmetic (LBP) to reconstruct the image of the sample. A filtering method has been used to eliminate the star noise owing to the LBP arithmetic. We find that the reconstructed images are very well consistent with the cross-section distribution of the samples.
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