Abstract
Layers occur when insoluble liquids meet each other such as water and oil. The monitoring of the interfaces among various liquid layers are of paramount importance for chemistry purifications, liquids storage in reservoirs, oil transportation, and chemical engineering. However, studies for layered liquid detection are limited. Visible examination has been used as a common practice to distinguish liquid layers, which is rough and in most cases hard to operate for chemical processing. In this paper, a long-period fiber grating (LPFG) based optical fiber sensor was investigated to detect the boundaries between layered liquids. The LPFG sensor when placed among the boundary of liquids will respond to the change of the refractive index between various liquid layers. Laboratory experiments showed that the refractive index difference between layers will induce a sudden change of the LPFG’s resonant wavelength if the LPFG sensor is bonded on an object when moving through the layer boundary. The LPFG sensor will have a higher sensitivity to detect the liquid layers when there is a bigger refractive index difference between the layered liquids. With further approval, the LPFG sensors could be potentially use for accurate liquid layer sensing which is highly demanded for chemical processing and liquid storage.
Highlights
Boundary occur between liquid and gas or insoluble liquids such as water-air, and water-oil
The detection of boundary between liquid-gas or insoluble liquids is significant during chemical processing, liquid storage and transportation such as the storage of oil and gas or hazard chemical products
Since these liquid level sensors have been in place for a long time, various technologies are available to detect the boundary between liquid and gas, including mechanical floating devices, hydronic pressure measuring devices [1], magnetic approaches [2], electrical conductivity measurements [3], capacitive sensing technology [4], ultrasonic and acoustic sensors [5], and others
Summary
Boundary occur between liquid and gas or insoluble liquids such as water-air, and water-oil. Every car, truck and motorcycle is equipped with a fuel level sensor to measure the amount of gasoline left in the fuel tank Since these liquid level sensors have been in place for a long time, various technologies are available to detect the boundary between liquid and gas, including mechanical floating devices, hydronic pressure measuring devices [1], magnetic approaches [2], electrical conductivity measurements [3], capacitive sensing technology [4], ultrasonic and acoustic sensors [5], and others. It is known that the effective index of the cladding mode depends on the refractive index of the surroundings, leading the long-period grating to be an effective sensor of the surrounding environments, which can be potentially used to detect liquid level changes. Durability, the proposed optical fiber sensing device could be applied for layered liquid detection in various applications such as fuel storage systems, chemical processing, and aerospace engineering
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