Vibratory Transducer Eigenmode Correction for Two-Phase Flow
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Solution Overview
Problem
Conventional inline measuring devices with vibratory transducers, such as Coriolis mass flow meters, face significant measurement errors when dealing with two-phase or multi-phase media, as the presence of gas bubbles or solid particles leads to fluctuations in oscillation measurement signals, making it difficult to accurately measure mass flow rate, density, and viscosity.
Innovation Solution
The method involves tracking and exciting specific natural eigenmodes of the measuring tube that are not directly excited by the exciter arrangement, allowing the mixture to dominate the vibration, and using eigenmode parameters to correct measurement errors, rather than relying on the classical bubble theory, which assumes direct coupling between density and mass flow errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional inline measuring devices use classical bubble theory to correct measurement errors, then the measurement process is simplified, but measurement precision deteriorates because the theory assumes direct coupling between density and mass flow errors which is not accurate for two-phase mixtures
Solution Approach 1:
The patent changes the fundamental parameters used for error correction from density-based corrections to eigenmode-based corrections. By monitoring parameters of natural eigenmodes (frequency, amplitude, phase) and using these to correct mass flow and density measurements, the system achieves higher precision without oversimplified assumptions about error coupling between density and mass flow.
2Duration of action of moving object
If the exciter arrangement directly excites the measuring tube, then the measuring tube vibration is maintained, but the ability to accurately detect mixture phase composition deteriorates because the exciter dominates the vibration signal
Solution Approach 1:
The patent segments the vibration signal into different eigenmode components. By separating the excitation frequency from the natural eigenmode frequencies, the system can monitor the natural modes that carry information about the mixture phase composition while the exciter maintains the overall vibration. This segmentation allows simultaneous vibration maintenance and accurate phase detection.
Solution Approach 2:
The natural eigenmodes act as intermediaries between the exciter and the mixture. The exciter provides energy to maintain vibration, while the natural eigenmodes respond to the mixture properties and carry the measurement information. This intermediary approach allows the system to maintain vibration without the exciter directly dominating the measurement signal.
3Ease of manufacture
If traditional classifiers are used to correct measurement errors in two-phase mixtures, then the correction method is established, but reliability deteriorates due to lack of transparency and difficulty in explaining the correction logic
Solution Approach 1:
The system uses the natural eigenmodes of the measuring tube itself to perform the correction, rather than relying on external classifiers or complex algorithms. The physical system's own characteristics (eigenmodes) provide the correction information, making the process more transparent and reliable while remaining easy to implement.
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
This approach allows for accurate measurement of mass flow rate and density in two-phase mixtures with errors less than 10% and corrects for both positive and negative errors, providing a more reliable and transparent method compared to traditional classifiers, with minimal changes required to the vibratory transducer and measurement circuit.
Implementation Method 1
the measuring tube is caused to vibrate, driven by an electromechanical exciter arrangement
Implementation Method 2
Coriolis mass-flow/density measuring device... by means of a transducer of the vibratory-type inserted into the course of the pipeline carrying the medium... which bring about reaction forces in the medium, such as e.g. Coriolis forces corresponding to the mass flow rate
Implementation Method 3
For registering vibrations of the tube segment, particularly at its inlet and outlet ends, the vibratory transducers additionally include an electrophysical sensor arrangement reacting to motions of the tube segment
Data Source
AI summary
The measuring device comprises, for measuring multi phase mixture, a vibratory-type transducer and a measuring device electronics electrically coupled with the vibratory-type transducer. The transducer includes at least one measuring tube inserted into the course of the pipeline. An exciter arrangement acts on the measuring tube for causing the at least one measuring tube to vibrate. A sensor arrangement senses vibrations of the at least one measuring tube and delivers at least one oscillation measurement signal representing oscillations of the measuring tube. Further, the measuring device electronics delivers an excitation current driving the exciter arrangement. The measuring device is adapted to compensating measurement errors, induced due to the presence of multi phase mixture, based on a movin resonator model (MRM).