Optical fiber probe to measure local void fraction profiles

A fiber optic probe for measuring the local void fraction in a two-phase (air-water) flow has been developed. The liquid-gas and gas-liquid interfaces are detected by the normal reflections of IR laser light at the tip of a multimode fiber. The probe and its associated electronic circuitry were calibrated by using the averaged void fraction measured by a quick closing valve system. The void profiles obtained by this method were compared with those obtained by a conductivity local probe. The proposed optical system shows a better sensitivity at high void fractions.