Coriolis Mass Flow Meter Stokes Number Viscosity Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mass flow sensors based on the Coriolis principle face significant relative measurement errors due to cross-sensitivity issues at smaller Reynolds numbers, particularly with increasing miniaturization, which are not effectively addressed by current correction methods using the Reynolds number.
Innovation Solution
The mass flow sensor and method compensate for cross-sensitivity by determining the Stokes number and correcting the provisional measured mass flow value based on the measurement error dependent on the Stokes number, specifically when the Reynolds number falls below a critical value, using a detailed evaluation and compensation process involving exciter signals, sensor signals, and viscosity measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Reynolds number-dependent correction is used, then measurement accuracy is improved for high Reynolds numbers (Re > 500), but measurement accuracy deteriorates at low Reynolds numbers
Solution Approach 1:
The patent changes the correction parameter from Reynolds number to Stokes number. The Stokes number (St = v/(f*D²)) differently characterizes the relationship between viscous forces and inertial forces in the context of vibrating measuring tubes, providing accurate correction for mass flow measurements across the entire Reynolds number range including low Re conditions where previous methods failed
2Volume of moving object
If miniaturization is increased, then device size is reduced, but measurement accuracy deteriorates due to cross-sensitivity to viscosity
Solution Approach 1:
By switching from Reynolds number correction to Stokes number correction, the patent enables accurate measurements in miniaturized sensors. The Stokes number accounts for the specific interaction between vibration frequency, tube dimensions, and fluid viscosity, which becomes increasingly important as sensor dimensions decrease, thereby maintaining measurement precision despite miniaturization
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 significantly reduces relative measurement errors, achieving accurate mass flow measurements even at low Reynolds numbers, with the correction being independent of flow velocity and Reynolds number, thereby improving the sensor's precision and reliability.
Implementation Method 1
Mass flow sensors based on the Coriolis principle
Implementation Method 2
at least two sensors for detecting the vibrations of the measuring tube and for outputting first and second sensor signals
Data Source
Figure 1a~1c
Figure 2~3
Figure 4a~4b
AI summary
The invention relates to a Coriolis mass flow meter (1), comprising: a measuring tube (21, 22) which can vibrate and which is for guiding a medium; at least one exciter (30) for bringing about vibrations in the measuring tube; at least two sensors (31, 32) for detecting the vibrations in the measuring tube (21, 22) and for outputting associated first and second sensor signals; and at least one operating and evaluating unit (90) for driving the exciter (30), in order to detect the sensor signals and to determine a mass flow measurement value based on a phase difference or time difference between the sensor signals, wherein the vibration behaviour of the measuring tube has a cross-sensitivity to the viscosity of the medium, wherein, for Reynolds numbers below a Reynolds number threshold, the cross-sensitivity correlates with a Stokes number, which is a gauge for a depth of penetration of the vibrations into the medium, wherein the operating and evaluating unit is configured to determine a current value of the Stokes number for Reynolds numbers below the lower Reynolds number threshold, and to compensate the influence of the cross-sensitivity according to the current value of the Stokes number in the determining of the mass flow.