Ultrasonic Flowmeter Viscosity Correction
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Solution Overview
Problem
Current ultrasonic flowmeters face challenges in accurately measuring flow rates and compositions of gas mixtures, particularly biogas, due to changing kinematic viscosity and complex composition, leading to inaccuracies and high production costs in multipath systems.
Innovation Solution
A method utilizing transit time difference measurements in a circular-cylindrical measuring tube with ultrasonic transducers to determine average flow velocity and kinematic viscosity, accounting for changing composition by real-time measurement of speed of sound and temperature, and calculating a modified Reynolds number to correct flow rate calculations, enabling accurate flow measurement in gas mixtures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transit-time difference measurement is used for flow rate determination, then the measurement is simple and cost-effective, but measurement precision deteriorates when kinematic viscosity changes due to composition changes in gas mixtures
Solution Approach 1:
The patent introduces an intermediary correction approach by measuring the speed of sound in the gas mixture and using it to calculate a correction factor based on kinematic viscosity changes. This correction factor compensates for the inaccuracies introduced by composition changes without requiring complex multipath systems, thus maintaining simplicity while improving precision.
Solution Approach 2:
The patent changes the measurement parameters by not only measuring transit time but also measuring the speed of sound and temperature. These additional parameters are used to calculate the kinematic viscosity and derive a correction factor, transforming a simple transit-time measurement into a multi-parameter measurement system that compensates for composition variations.
2Measurement precision
If multipath systems with multiple ultrasonic transducers are used, then measurement precision improves for flow profile measurement, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts only the essential information needed for correction - the speed of sound measurement - from a full multipath system. Instead of using multiple transducer pairs to measure flow profile, it uses a single transducer pair for transit-time measurement and separates the viscosity correction function, thereby reducing device complexity while maintaining precision.
Solution Approach 2:
The patent makes the ultrasonic transducer serve multiple functions: it is used both for the primary transit-time flow measurement and for measuring the speed of sound (by sending pulses in both directions). This multi-functionality eliminates the need for additional transducers that would be required in a multipath system, reducing complexity while maintaining measurement precision through the correction factor.
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 method provides highly accurate flow rate measurements in gas mixtures by accounting for changing kinematic viscosity and composition, reducing errors and production costs compared to traditional multipath systems.
Implementation Method 1
The transit-time difference principle evaluates the different transit times of ultrasonic pulses relative to the flow direction of the liquid. For this purpose, ultrasonic pulses are sent at a specific angle to the pipe axis, both with and against the flow.
Implementation Method 2
ultrasonic pulses are sent at a specific angle to the pipe axis, both with and against the flow
Implementation Method 3
In the Doppler principle, ultrasound waves of a specific frequency are coupled into the liquid, and the ultrasound waves reflected by the liquid are analyzed. The flow velocity of the liquid can also be determined from the frequency shift between the coupled and reflected waves.
Implementation Method 4
Ultrasonic transducers typically consist of an electromechanical transducer element, such as a piezoelectric element, and a coupling layer. The ultrasonic waves are generated in the electromechanical transducer element
Implementation Method 5
Between the piezoelectric element and the coupling layer, another coupling layer, a so-called matching layer, can be arranged. The matching layer performs the function of transmitting the ultrasound signal and simultaneously reducing reflections caused by differing acoustic impedances at interfaces between two materials.
Data Source
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AI summary
A method for determining the flow rate of a fluid, which is a gas mixture, wherein at least one component of the gas mixture is a hydrocarbon, through a circular cylindrical measuring tube with a straight measuring tube longitudinal axis and an internal diameter DI, characterized by the following method steps: determining a first average flow velocity vL by measuring the propagation time difference of acoustic signals along a signal path; determining a modified Reynolds number Remod according to the formula Remod = (vL*DI)/vkin, wherein vkin, the kinematic viscosity of the fluid, is known; determining a second average flow velocity vA using a known function vA = f(Remod) on the basis of the modified Reynolds number Remod, wherein the method step of determining the modified Reynolds number Remod is preceded by the method step of determining the kinematic viscosity vkin of the fluid.