Vibratory Flowmeter Phase Fraction Adjustment for Multiphase Accuracy
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Solution Overview
Problem
Coriolis flowmeters face accuracy degradation when measuring multiphase fluids due to fluid decoupling caused by entrained gas and solids, leading to under-reported flow and density errors, and existing methods for compensating drive gain are inadequate, especially in applications with small gas amounts or variable fluid conditions.
Innovation Solution
A vibratory meter system that measures drive gain and total density to determine phase fraction composition, allowing for accurate calculation of flow rates for each liquid phase, with adjustable thresholds to account for varying fluid conditions and minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Coriolis flowmeter is used to measure multiphase fluids, then mass flow and density can be measured, but measurement precision is significantly degraded due to fluid decoupling
Solution Approach 1:
The system changes the measurement approach by introducing a phase fraction measurement parameter. When gas-liquid two-phase flow is detected, the system calculates the liquid phase flow rate using the formula: Liquid Flow Rate = Total Flow Rate × (1 - Gas Volume Fraction). This parameter change allows accurate measurement despite fluid decoupling by compensating for the gas phase presence.
Solution Approach 2:
The system uses an intermediary calculation method that introduces phase fraction determination as a mediator between the total flow measurement and the actual liquid flow calculation. By determining the gas volume fraction through drive gain analysis and density measurements, the system creates an intermediate step that compensates for the decoupling effect of gas bubbles.
2Measurement precision
If drive gain compensation methods are used, then some measurement errors can be reduced, but they are inadequate for applications with small gas amounts or variable fluid conditions
Solution Approach 1:
The system implements dynamic adaptation by continuously monitoring drive gain and density measurements to detect changes in fluid phase composition. The gas volume fraction calculation is dynamically updated based on real-time drive gain deviations and density readings, allowing the system to adapt to varying gas amounts and fluid conditions without requiring manual reconfiguration.
Solution Approach 2:
The system uses feedback from drive gain measurements and density readings to continuously refine the phase fraction determination. The drive gain deviation from expected single-phase values provides feedback that triggers phase fraction calculations, and the resulting gas volume fraction is fed back into the flow rate compensation equation for continuous improvement of measurement accuracy under varying conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves flowmeter accuracy by accurately measuring flow rates and densities in multiphase fluids, reducing errors associated with fluid decoupling and varying gas content, and enabling more precise fluid management in applications like restaurant grease trap recycling.
Implementation Method 1
The driver may comprise one of many well-known arrangements such as a piezo driver or a magnet having an opposing drive coil. An alternating current is passed to the driver for vibrating the conduit(s) at a desired amplitude and frequency.
Implementation Method 2
the pickoffs can use the motion provided by the driver to induce a voltage. The magnitude of the time delay measured by the pickoffs is very small; often measured in nanoseconds.
Implementation Method 3
The relative motion of the gas bubbles with respect to the liquid is driven by a buoyant force that is similar to the force that causes bubbles to rise to the surface under the influence of gravity. However, in a vibrating tube, it is the acceleration of the vibrating tube that causes the bubbles to move more than the acceleration of gravity.
Implementation Method 4
Some types of mass flowmeters, especially Coriolis flowmeters, are capable of being operated in a manner that performs a direct measurement of density to provide volumetric information through the quotient of mass over density.
Data Source
AI summary
A vibratory meter (5) is provided, having a driver (104) and a vibratory member (103, 103′) vibratable by the driver (104). At least one pickoff sensor (105, 105′) is configured to detect vibrations of the vibratory member (103, 103′). Meter electronics (20) comprise an interface (301) configured to receive a vibrational response from the at least one pickoff sensor (105, 10540 ), and a processing system (303) coupled to the interface (301). The processing system (303) is configured to measure a drive gain (306) of the driver (104), and measure a total density (325) of a multiphase process fluid in the vibratory meter (5), and determine whether the drive gain (306) is below a first threshold. A liquid/liquid phase concentration allocation is determined with the measured total density (325) if the drive gain (306) is below the first threshold, and a flow rate for each liquid phase is calculated.