Gas-Liquid Flow Measurement Using Annular Slip Correction
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Solution Overview
Problem
Current methods for measuring gas and liquid flow rates in gas-liquid mixed fluids are prone to errors due to gas-liquid slip, lack precision, and are not suitable for automation, especially in challenging environments like oil fields in deserts or oceans, as they require complex separators and rely on empirical models that are not universally applicable.
Innovation Solution
A method involving a vertically arranged circular pipe to form a stable gas-liquid two-phase annular flow, where the gas surrounds the pipe axis and liquid is distributed between the gas and the pipe wall, allowing for precise measurement of total volume flow rate, temperature, pressure, and gas volume fraction, and subsequent calculation of gas and liquid flow rates using specific equations to correct for gas-liquid slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separator is used to separate gas and liquid phases for measurement, then the volume flow rates of both phases can be measured, but the device becomes complex, occupies large space, and requires complex control and maintenance
Solution Approach 1:
The patent extracts the measurement function from the complex separator system and implements it directly in the mixed flow using a probe. The probe measures parameters (pressure differential, temperature, sound velocity) of the mixed gas-liquid flow, and the gas volume fraction is calculated from these parameters, eliminating the need for physical separation and complex measurement equipment.
2Device complexity
If theoretical calculation methods are used assuming equal gas and liquid velocities, then the measurement process is simplified, but measurement errors increase due to gas-liquid slip
Solution Approach 1:
The patent introduces a feedback mechanism by using measured parameters (pressure differential, temperature, sound velocity) to calculate the gas volume fraction, which then corrects the flow rate measurements. This feedback loop compensates for the gas-liquid slip effect without requiring complex additional equipment, thereby improving measurement precision while maintaining relatively simple device structure.
3Measurement precision
If empirical models are used to correct gas-liquid slip, then measurement precision can be improved, but the models lack universal applicability and depend strongly on experimental data
Solution Approach 1:
The patent changes the measurement parameters from direct flow rate measurement to measuring fundamental physical parameters (pressure differential, temperature, sound velocity) of the mixed flow. By calculating the gas volume fraction from these fundamental parameters and using it to correct both gas and liquid flow rates, the method achieves universal applicability across different flow conditions while maintaining high measurement precision.
Data Source
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AI summary
A flow metering method for an annular gas and liquid flow comprises the following steps of: first, enabling a gas and liquid mixed fluid to flow through a vertically arranged circular pipe so as to form the annular gas and liquid flow; and then measuring total flow or liquid average velocity or gas average velocity of the gas and liquid mixed fluid; measuring physical quantities, such as temperature, pressure, gas fraction and the like, of the gas and liquid mixed fluid; and finally, accurately figuring out liquid volume flow and gas volume flow according to analysis of a gas and liquid slip factor.