Vibration-Type Flow Meter Eigenfrequency Correction
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Solution Overview
Problem
Existing flow meters with multiple measuring tube pairs face challenges in accurately determining the density and mass flow of compressible media due to measurement errors caused by compressibility, especially when dealing with gas-containing media and suspended bubbles, which affect the eigenfrequencies of the oscillating modes.
Innovation Solution
A method using a measuring transducer with two independently oscillating measuring tube pairs, where each pair has distinct eigenfrequencies for corresponding modes, allowing for the determination of preliminary density values and correction terms based on eigenfrequencies, velocity of sound, and mass flow errors, to accurately account for the compressibility effects and correct measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two curved measuring tube pairs are mechanically coupled to achieve shared eigenfrequency for greater flow rates, then flow measurement capability is improved, but the ability to excite stable f3 mode is interfered with and measurement precision deteriorates
Solution Approach 1:
The measuring transducer is divided into two independent oscillator systems, each with its own measuring tube pair. The first oscillator has measuring tubes with first eigenfrequency and the second oscillator has measuring tubes with second eigenfrequency. This segmentation allows each oscillator to independently measure different parameters without mutual interference, resolving the contradiction between flow measurement capability and measurement precision.
Solution Approach 2:
The patent introduces an intermediary calculation approach where the ratio of eigenfrequencies from two independent oscillators is used as a mediator to determine the compressibility of the medium. This intermediary method allows accurate density and flow measurement by using the eigenfrequency ratio as an intermediate step to correct for compressibility effects.
2Device complexity
If measuring tubes are mechanically coupled with substantial couplers to achieve same eigenfrequency, then device compactness is improved, but compressibility correction capability is worsened
Solution Approach 1:
Instead of mechanically coupling measuring tubes with substantial couplers, the patent segments the system into two independently oscillating systems. Each oscillator maintains its own eigenfrequency characteristics, allowing the system to remain compact while preserving the ability to measure and correct for compressibility effects through the ratio of eigenfrequencies.
Solution Approach 2:
The patent changes the approach from mechanical coupling (physical parameter) to eigenfrequency ratio comparison (dynamic parameter). By using the ratio of eigenfrequencies from two independent oscillators as the measurement parameter, the system achieves compactness without sacrificing compressibility correction capability.
3Measurement precision
If eigenfrequencies of f1 mode and f3 mode are evaluated to ascertain velocity of sound for compressibility correction, then measurement accuracy for compressible media is improved, but device complexity increases
Solution Approach 1:
The measuring transducer uses its own eigenfrequencies from two independent oscillators to self-determine the compressibility of the medium. The system serves itself by using the ratio of its own eigenfrequencies (f1 and f3 modes) to calculate the velocity of sound and apply compressibility corrections, without requiring external reference measurements or additional complex equipment.
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 enhances the accuracy of density and mass flow measurements by considering the unique eigenfrequencies and compressibility influences, reducing errors and providing precise corrections for compressible media, including gas-containing mixtures and suspended bubbles.
Implementation Method 1
the measuring tube has bending oscillation modes, whose eigenfrequencies depend on the density of the medium
Implementation Method 2
whose eigenfrequencies depend on the density of the medium
Implementation Method 3
Compressible media oscillate relative to an oscillating measuring tube, which leads to a change of the eigenfrequency of the measuring tube
Implementation Method 4
The closer the resonance frequency of the medium approximates the eigenfrequency of the considered bending oscillation mode, the greater is the change of the eigenfrequency
Implementation Method 5
the eigenfrequencies of the f1 mode and the f3 mode are evaluated, to ascertain the velocity of sound in the medium
Data Source
AI summary
A method for determining density and/or mass flow of a compressible medium with a measuring transducer of vibration-type having at least two oscillators, each including a pair of measuring tubes, wherein the pairs of measuring tubes are arranged for parallel flow, wherein the two oscillators have mutually independent oscillator oscillations with mutually differing eigenfrequencies for corresponding oscillation modes. The method includes steps of determining the values of the eigenfrequencies of at least two different oscillator oscillations, determining at least two preliminary density measured values based on the values of the eigenfrequencies, and determining a correction term for one of the preliminary density measured values and/or for a preliminary measured value of flow based on the preliminary density measured values and the values of the eigenfrequencies.