Ultrasonic Flow Sensor Resonance Matching Variable Pipe Walls
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Solution Overview
Problem
Ultrasonic flow meters face challenges in achieving a sufficient signal-to-noise ratio due to the dominance of structural borne signals over fluid borne signals when sensing fluid flow within pipes, particularly in clamp-on applications where signal back reflection occurs at metal-fluid interfaces.
Innovation Solution
The solution involves using ultrasonic sensors with transmitters and receivers aligned to match half-wave resonant frequencies of the pipe walls, and employing acoustic members like shims or high impedance blocks to balance the resonant frequencies of the transmit and receive walls, thereby minimizing signal transmission loss and enhancing the fluid borne signal component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ultrasonic sensors are used in clamp-on applications to detect fluid flow, then the ability to measure flow without interrupting service is improved, but the signal-to-noise ratio deteriorates due to dominance of structural borne signals over fluid borne signals
Solution Approach 1:
The patent applies resonance by tuning the ultrasonic transmitter frequency to match the half-wave resonant frequency of the pipe wall. This causes the pipe wall to vibrate in resonance, significantly amplifying the fluid-borne signal component while the structural-borne signal does not benefit from resonance enhancement, thereby improving the signal-to-noise ratio
Solution Approach 2:
The patent changes the operating frequency parameter of the ultrasonic transmitter to specifically match the resonant frequency of the pipe wall. This parameter adjustment transforms the system response, creating a condition where the fluid-borne signal is preferentially amplified through resonant coupling
2Adaptability or versatility
If pipe walls have unbalanced thicknesses at transmit and receive locations, then installation flexibility is improved, but transmission loss increases due to mismatched resonant frequencies
Solution Approach 1:
The patent applies different local modifications to the pipe wall at the transmit and receive locations. Specifically, it adds or removes material (such as using shims or machining) to create local resonant frequency adjustments, ensuring that each location's resonant frequency matches the transmitter frequency despite overall pipe wall thickness variations
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 improves the signal-to-noise ratio by reducing transmission loss, increasing the amplitude of the fluid borne signal, and enhancing the operational performance of ultrasonic flow meters, even in scenarios with unbalanced pipe wall thicknesses.
Implementation Method 1
the combined respective member and pipe wall have half wave resonant frequencies that substantially match the half wave resonant frequencies of the opposite wall
Implementation Method 2
transmitter operable to transmit ultrasonic signals through the first pipe wall, fluid flow disposed within the pipe, and the second pipe wall
Implementation Method 3
receiver operable to receive the transmitted signal after the signal has passed through the first and second pipe walls and the fluid flow disposed within the pipe
Data Source
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AI summary
A method and apparatus for sensing a fluid flow within a pipe is provided. The method includes the steps of: a) providing an ultrasonic sensor having a transmitter operable to transmit ultrasonic signals through the first pipe wall, the fluid flow disposed within the pipe, and the second pipe wall, and a receiver operable to receive the transmitted signal after the signal has passed through the pipe walls and fluid flow; b) disposing the transmitter adjacent the first wall and the receiver adjacent the second wall; c) disposing at least one acoustic member between at least one of the transmitter and the first wall, and the receiver and the second wall, which acoustic member has acoustic properties such that the combined respective member and pipe wall have half wave resonant frequencies that substantially match the half wave resonant frequencies of the opposite wall, or opposite wall and respective member; and d) sensing the fluid flow through the pipe walls and structure using the ultrasonic sensor.