Modifications of the Separationless Oil–Water–Gas Flowmeter with a Dual Isotope Gamma-Densitometer for Particular Cases of Applications

On the basis of a three-phase horizontal flowmeter with a nominal diameter DN 100, options for designing and creating relatively simple two-phase flowmeters without devices for measuring the average density of a mixture of low-viscosity flows, e.g., water–gas, are proposed using only conical narrowing devices (NDs) of various sizes, which are characterized by such features as the crisis of the hydraulic resistance in NDs and various quantitative characteristics that describe this crisis. A calculation and experimental method is proposed that demonstrates the principal possibility of finding the gas volume fraction β using pressure drops ∆Р at both NDs. An unusual calculation model is proposed based on the need to know a pair of measured pressure drops’ ∆P values and preliminary experimental calibration dependences ∆P(β) for both NDs at different volumetric liquid flow rates Q₁, and it is shown that the resulting errors in determining Q₁ and β are quite acceptable for practice in some cases. A universal design of a two-phase flowmeter has been proposed and created, thus allowing the operation with liquid–gas flows not only of relatively low viscosity, but also of comparatively high viscosity, as well as with two-phase liquid flows. This flowmeter is based on a combination of a pair of NDs and a tuning fork densitometer, thus providing a measurement accuracy acceptable for practice. A variant of a three-phase oil–water–gas flowmeter is also presented.