Multi-phase-fluid discrimination with local fibre-optical probes: III. Three-phase flows

Abstract

Local fibre-optical sensors (or `local probes') for immiscible-fluid discrimination are demonstrated in three-phase (oil/water/gas) flows. The probes are made from standard silica fibres with plane oblique facets polished at the fibre tip, with surface treatment for wettability control. They use total internal reflection to distinguish among drops, bubbles and other regions of fluid in multi-phase flows, on the basis of refractive-index contrast. Dual probes, using two sensors each with a quasi-binary output, are used to determine profiles of three-phase volume fraction in a flow of kerosene, water and air in a pipe. The individual sensors used discriminate oil from `not-oil' and gas from liquid; their logical combination discriminates among the three phases. Companion papers deal with the sensor designs used and quantitative results achieved in the simpler two-phase cases of liquid/liquid flows and gas/liquid flows.

Sensor‐based flow pattern detection—gas–liquid–liquid upflow through a vertical pipe

“…A survey of the past literature reveals that the most commonly used optical technique in two‐ and three‐phase flows is the optical fiber probe (Piela et al, Fordham et al). It is based on either Fresnel reflectivity or total internal reflection of light emitted from the fiber tip and is a measure of the refractive index contrast.…”

“…It can also identify small fluid elements due to scattering of light at the interface. The past researchers working with fiber optic probe have reported (Fordham et al) that for three‐phase flows, a single sensor often fails to discern the three‐phase distribution and a combination of dual sensors is necessary to distinguish gas–liquid and “oil–not oil” components of the mixture. In the present study, we have used a single probe to identify the flow patterns for water predominant, oil predominant, and air predominant flow conditions.…”

Research Progress of the Optical Fiber Sensors in Process Tomography

“…The method can set the fiber probe to detect gas=liquid containing gas production and identify bubbles. [7][8][9] Hardware Basic Structure of Optical Fiber Process Tomography…”

Multi-Scale Long-Range Magnitude and Sign Correlations in Vertical Upward Oil–Gas–Water Three-Phase Flow

“…Later, some researchers investigated the three-phase flow characteristics by using the pressuregradient technique [2][3][4], computerised tomography [5], and photography [6,7]. The local fluid properties of threephase flows were detected by introducing the local optical probe [8,9], local conductivity probe [10,11], and gammaray densitometry [12,13]. Moreover, the flow pattern transition in oil-gas-water flows has attracted substantial attention [4,7,14].…”