Research

4-Point Optical Fiber (Quartz and Plastic) Probes for gas-liquid and gas-liquid-solid systems(Moses)

Two techniques of 4-point optical probe are available; one for quartz glass fibers and another for plastic tubes. This technique measures bubble cord length, velocity, frequency, direction, local gas velocity in axial direction, specific interfacial area, and local gas velocity. It consists of four tips; three of which are of the same length and form an equilateral triangle. The fourth central tip is positioned through the inertial center of this triangle and is about 2.0 mm longer than the others. Each fiber consists of three layers: a quartz glass core of 200 µm in diameter having a refraction index of 1.45, a silicon cladding of 380 µm in diameter and a protective layer of Teflon of 600 µm in diameter. The light is sent into each fiber by an LED via standard glass fiber connectors and is detected by a photodiode. Due to the difference in the refractive index, the fiber tip reflects different amounts of light when the tip is in liquid or gas phase. The reflected light finally transforms the light photons into a voltage signal which can be analyzed to get the required measurements.

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