Karman Vortex Flowmeter Piezoelectric Sensor Corrosion Protection
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Solution Overview
Problem
Conventional Karman vortex flowmeters have complex structures that increase manufacturing costs and may not enhance detection accuracy due to isolated vibration pick-up elements, and are prone to corrosion from corrosive gases that permeate the pressure-receiving pieces.
Innovation Solution
A Karman vortex flowmeter design featuring a thin film part with higher corrosion resistance than the electrode, sandwiched between plate-shaped parts and the electrode, to prevent corrosion and improve vibration transmissibility, with the thin film part's thickness optimized to balance corrosion protection and vibration transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diaphragm is used to isolate the vibration pick-up element from the flow passage, then the structure provides protection, but the manufacturing cost increases and detection accuracy is compromised
Solution Approach 1:
The invention extracts the vibration pick-up element from the flow passage environment by housing it in a pressure-receiving piece that is fixed to the pipe wall, removing it from direct exposure to the fluid while maintaining detection capability through the pressure-receiving plate
Solution Approach 2:
The vibration pick-up element is nested within the pressure-receiving piece housing, which itself is fixed to the pipe wall. This nested structure provides protection while maintaining a compact design that reduces overall complexity compared to diaphragm-based isolation systems
2Measurement precision
If the vibration pick-up element is arranged in the flow passage to improve detection accuracy, then detection sensitivity improves, but corrosive gas permeates the housing and corrodes the electrode
Solution Approach 1:
A thin film part with higher corrosion resistance than the electrode is introduced as an intermediary layer between the corrosive environment and the electrode. This thin film allows vibration transmission while blocking corrosive gas permeation, protecting the electrode without compromising detection accuracy
Solution Approach 2:
The pressure-receiving piece uses composite construction with a thin film part having superior corrosion resistance properties compared to the main housing material. This composite structure provides both corrosion protection and vibration transmission capability, solving the contradiction between exposure to corrosive gases and detection sensitivity
3Reliability
If a thin film part with high corrosion resistance is added to protect the electrode, then corrosion protection improves, but the structure becomes more complex and manufacturing cost increases
Solution Approach 1:
The invention uses a thin film part that is flexible enough to transmit vibrations from the pressure-receiving plate to the piezoelectric element while being thin enough to be integrated into the existing housing structure. This thin film approach provides corrosion protection without significantly increasing structural complexity or manufacturing cost
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
The design effectively suppresses electrode corrosion from corrosive gases while enhancing the sensitivity and accuracy of the piezoelectric element by improving vibration transmissibility, reducing manufacturing complexity and costs.
Implementation Method 1
a Karman vortex flowmeter that measures a Karman vortex to thereby obtain a flow rate of a fluid
Implementation Method 2
surroundings of the thin film part are filled with the adhesive, thereby transmissibility of the vibration due to the Karman vortexes can be improved, and sensitivity of the piezoelectric element can be improved in connection with the improvement of the transmissibility of the vibration
Data Source
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AI summary
There is provided a Karman vortex flowmeter including: a body inside which a flow passage and a Karman vortex generation column are formed; and a flow rate measurement unit that measures Karman vortexes generated by the Karman vortex generation column to thereby obtain a flow rate of a fluid, in which the flow rate measurement unit includes: a piezoelectric element; a piezoelectric element holder that is attached to the body so that the piezoelectric element is arranged in a flow passage; and a thin film part that is formed of a material with higher corrosion resistance than an electrode of the piezoelectric element, the piezoelectric element holder houses the piezoelectric element in a state where the piezoelectric element is sandwiched by a pair of plate-shaped parts integrally formed by a resin material, and in which the thin film part is arranged between the plate-shaped parts and the electrode.