Chordal Gas Flowmeter Housing with Acoustic-Isolated External Transducers
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Solution Overview
Problem
Current ultrasonic gas meters face challenges such as poor signal-to-noise ratios, acoustic losses, and the need for special tools or depressurization to replace transducers, which pose safety hazards and disrupt pipeline flow, due to transducers being directly exposed to gas and using traditional housings that do not match acoustic impedance.
Innovation Solution
The flowmeter design features transducers housed in pressure-containing compartments with acoustic isolators, using thin titanium windows and composite piezoelectric transducers, allowing safe replacement without depressurization and improving signal strength through acoustic isolation and impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If transducers are placed outside the pressure boundary with traditional housings, then transducer replacement is easier, but acoustic signal quality deteriorates due to impedance mismatch and noise
Solution Approach 1:
A thin titanium window serves as an intermediary element between the transducer and the gas flow. This window provides acoustic impedance matching, allowing efficient transmission of ultrasonic signals while maintaining the pressure boundary. The transducer can be replaced by removing the entire housing unit through the access opening, and the thin window ensures good acoustic coupling without requiring the transducer to be in direct contact with the gas.
2Measurement precision
If transducers are in direct contact with gas, then acoustic coupling is improved, but transducer safety and replaceability worsen due to high pressure and corrosive gases
Solution Approach 1:
A thin titanium window (less than 1/4 wavelength of the ultrasonic frequency) is used as a flexible yet strong barrier. This thin film provides adequate acoustic coupling for ultrasonic signals while maintaining the pressure boundary and protecting the transducer from corrosive gases like hydrogen sulfide. The thinness of the window minimizes acoustic impedance mismatch while still providing mechanical strength and chemical protection.
3Strength
If traditional thick metal windows are used in transducer housings, then structural strength is improved, but acoustic transmission deteriorates due to impedance mismatch
Solution Approach 1:
The window thickness is changed to be less than 1/4 of the ultrasonic wavelength, which fundamentally changes the acoustic transmission characteristics. This parameter change allows the window to be acoustically transparent while maintaining structural integrity. The thin titanium window provides both the necessary mechanical strength to contain pressure and the acoustic transparency to transmit ultrasonic signals efficiently.
4Stability of the object's composition
If rigid attachments are used to secure transducer housings, then mechanical stability is improved, but acoustic noise increases due to vibration transmission
Solution Approach 1:
Acoustic isolation elements serve as intermediaries between the transducer housing and the meter body. These elements decouple the rigid mechanical connection while allowing the housing to remain mechanically stable. The isolation elements prevent vibration and acoustic noise from being transmitted through the meter body, improving the signal-to-noise ratio while maintaining the structural stability needed for proper transducer positioning.
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 achieves accurate gas flow measurements with enhanced signal-to-noise ratios and safe transducer replacement, reducing operational risks and maintaining pipeline flow, while withstanding high pressures and corrosive gases like hydrogen sulfide.
Implementation Method 1
broad band piezoelectric composite transducer with a coupling coefficient greater than 0.7 out of 1 and an acoustic impedance of less than 34 MRayls
Implementation Method 2
thin titanium windows and composite piezoelectric transducers, allowing safe replacement without depressurization and improving signal strength through acoustic isolation and impedance matching
Implementation Method 3
acoustic isolators which acoustically isolate the transducer housings from the container
Data Source
Figure 1
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AI summary
A flowmeter for detecting gas flow rates in a pipe includes a container configured to be attached to the pipe having a channel through which the gas flows, and a plurality of recesses that extend through the container and a plurality of housings. Each recess has a housing which contains pressure in the channel. Each housing has a window that is in acoustic communication with the channel. The flowmeter includes a plurality of transducers, with one transducer of the plurality of transducers disposed in each recess. The transducers transmit ultrasonic signals into and receive ultrasonic signals from the channel through the window in the housing in which a transducer is disposed. The flowmeter includes a controller in electrical communication with the plurality of transducers which determines the gas flow rate through the channel by measuring transit times of signals transmitted by and received by the transducers. A housing for an ultrasonic transducer for a flowmeter which is inserted into a recess of a container that acoustically isolates the housing from the container. A method for detecting gas flow rates in a pipe. A transducer for an ultrasonic flowmeter.