Cryogenic Void Fraction Sensor Layout for Accurate Hydrogen Flow
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Solution Overview
Problem
Accurate measurement of the flow rate of liquid hydrogen is challenging due to its low boiling point and high thermal conductivity, causing rapid vaporization and fluctuating gas-to-liquid ratios, which complicates the determination of flow rates in industrial applications.
Innovation Solution
A void fraction sensor with a specific electrode configuration and insulating pipe design that measures the void fraction in cryogenic two-phase flows, using a pair of planar electrodes mounted on an insulating pipe with optimized distances and shapes to enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional flow velocity meter is used to measure liquid hydrogen flow rate, then the measurement is simple, but the measurement accuracy is poor due to fluctuating gas-to-liquid ratios and immediate vaporization
Solution Approach 1:
The measurement system is segmented into two independent components: a flow velocity meter that measures liquid velocity and a void fraction sensor that measures gas volume percentage. These separate measurements are then combined to calculate the accurate flow rate, resolving the contradiction by dividing the complex measurement task into manageable parts.
Solution Approach 2:
The void fraction sensor acts as an intermediary device that provides additional information about the two-phase flow composition. By introducing this intermediate measurement, the system can accurately determine flow rate even in the presence of fluctuating gas-to-liquid ratios and vaporization.
2Measurement precision
If the distance between inner wall surfaces in the direction perpendicular to electrode surfaces is made shorter to improve void fraction measurement sensitivity, then the measurement precision is improved, but the pressure loss increases and stress concentrations occur
Solution Approach 1:
The insulating pipe has different distance characteristics at different locations: in the electrode mounting portions where measurement precision is critical, the distance D1 between inner wall surfaces perpendicular to electrode surfaces is made shorter, while in other portions the distance D2 is maintained longer to reduce overall pressure loss and stress concentrations. This local optimization resolves the contradiction.
3Measurement precision
If the distance between inner wall surfaces in the direction perpendicular to electrode surfaces is made shorter to improve measurement sensitivity, then the void fraction measurement precision is improved, but the stress concentrations increase reducing longevity
Solution Approach 1:
The insulating pipe structure implements local quality by having shorter distance D1 only in the electrode mounting portions where measurement precision is required, while maintaining longer distance D2 in other portions. This localized design achieves high measurement precision without creating excessive stress concentrations that would reduce overall sensor longevity and reliability.
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 sensor provides precise measurement of void fraction, enabling accurate determination of cryogenic liquid flow rates by minimizing pressure loss and reducing stress concentrations, thus improving measurement reliability and longevity.
Implementation Method 1
Non-Patent Document 1 has proposed a capacitance-type void fraction sensor that measures capacitance using a pair of electrodes
Data Source
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AI summary
A void fraction sensor according to the present disclosure includes an insulating pipe having a through hole through which a cryogenic liquid flows, and a pair of planar electrodes mounted on an outer wall surface of the insulating pipe. The insulating pipe has electrode mounting portions at which a distance D1 between inner wall surfaces in a direction perpendicular to electrode surfaces of the pair of planar electrodes is shorter than a distance D2 between inner wall surfaces in a direction parallel to the electrode surfaces of the pair of planar electrodes.