Local void fraction measurements in two-phase flow with an optical fibre probe

摘要

We report on an opticla fibre probe and the corresponding electronic equipment for signal processing.this was develoed in order to study local and temeporal changes in structures of gas-liquid flows.Local void fractions and bubble frequencies were measured in vertical flows of ir and water in a transparent tube.In the mising chember the air was introduced through a porous ceramic tube or sveral brass tubes with a different number of holes.Superficial air and water velocities were used as variable parameters.The global void fractin was measured by a #gamma# densitometer just downstream the fibre probe.We observed three different types of bubble flow: most bubbles close to the wall (sliding flow),most bubbles in the tube axis (coring flow) and an intermediate structure.Small bubbles may coalesce to large bubbles.By this,a transition occurs from bubble to slug flow.