Ultrasonic Transducer Coupling Element for Flow Meter Wave Mode Conversion
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Solution Overview
Problem
Conventional ultrasonic transducers for flow meters suffer from interference due to the coupling of both transverse and longitudinal waves into the pipeline, which disrupts the measurement of flow velocity using the transit time difference principle.
Innovation Solution
The ultrasonic transducer design incorporates a second boundary surface and carefully selected angles between surfaces to maximize the coupling of transverse waves while minimizing the coupling of longitudinal waves, ensuring that most longitudinal waves are reflected back into the coupling element and not into the pipeline, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasonic transducers are used to couple longitudinal waves into the pipeline, then the transducer can generate and transmit ultrasonic signals, but longitudinal waves interfere with the measurement of flow velocity using the transit time difference principle
Solution Approach 1:
The coupling element is designed with different acoustic properties for different regions: the first coupling surface has a first acoustic impedance and the second coupling surface has a second acoustic impedance. This local differentiation of acoustic properties allows selective coupling of transverse waves at the first surface while minimizing longitudinal wave coupling at the second surface, thereby reducing interference with flow velocity measurement.
Solution Approach 2:
The invention changes the acoustic impedance parameters of the coupling element by introducing a second coupling surface with different acoustic properties. By carefully selecting the acoustic impedance of the second coupling surface, the patent minimizes the coupling of longitudinal waves while maintaining the coupling of transverse waves, thus improving measurement precision.
2Measurement precision
If the coupling element is designed to maximize transverse wave coupling, then flow velocity measurement improves, but longitudinal wave coupling increases causing interference
Solution Approach 1:
The coupling element is designed with different acoustic properties for different regions: the first coupling surface has a first acoustic impedance and the second coupling surface has a second acoustic impedance. This local differentiation of acoustic properties allows selective coupling of transverse waves at the first surface while minimizing longitudinal wave coupling at the second surface, thereby reducing interference with flow velocity measurement.
Solution Approach 2:
The invention utilizes the reflection of longitudinal waves at the second coupling surface, which initially appears as a harmful effect, and converts it into a beneficial outcome. By designing the second coupling surface with specific acoustic impedance, the reflected longitudinal waves are directed back into the coupling element rather than into the pipeline, transforming the potential interference into a wave management mechanism that reduces harmful coupling.
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 design enhances the accuracy of flow measurements by minimizing disruptive reflections, allowing for more precise determination of flow velocity using the transit time difference principle, and is suitable for high-temperature applications.
Implementation Method 1
The coupling element is suitable for mode conversion of an acoustic longitudinal wave between an input coupling surface and an output coupling surface of the coupling element by reflection at a first interface of the coupling element to a predetermined medium
Implementation Method 2
ultrasonic transducers typically consist of an electromechanical transducer element, such as a piezoelectric element
Data Source
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AI summary
The invention relates to a coupling element of an ultrasonic transducer for an ultrasonic flow meter, suitable for mode conversion of an acoustic longitudinal wave between a coupling input surface and a coupling output surface of the coupling element by reflection at a first boundary of the coupling element to a prescribed medium, wherein the coupling element comprises a second boundary to a prescribed medium, wherein a first angle between the coupling input surface and the first boundary and a second angle between the first boundary and the coupling output surface are selected so that a portion of transverse waves is reflected at the first boundary to the coupling output surface, and wherein the first angle between the coupling input surface and the first boundary and a third angle between the first boundary and the second boundary are selected so that a portion of the longitudinal waves is reflected at the first boundary to the second boundary, and that a portion of the longitudinal waves reflected to the second boundary is reflected back into the coupling element at the second boundary, wherein the centroid of the second boundary is offset to a plane in the direction of the surface normals of the coupling output surface through the centroid of the coupling output surface, to which plane the surface normal of the coupling output surface is perpendicular and in which plane the centroid of the coupling output surface lies.