Capacitive Void Fraction Sensor for Cryogenic Hydrogen Flow Measurement
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Solution Overview
Problem
Existing methods fail to accurately measure the flow rate of liquid hydrogen due to its volatile nature and fluctuating gas-to-liquid ratio, leading to inaccurate determination of flow rates in industrial applications.
Innovation Solution
A void fraction sensor with a unique insulating pipe design and planar electrodes that measure capacitance, optimizing electrode placement and pipe geometry 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, then the flow velocity can be obtained, but the flow rate cannot be accurately determined due to fluctuating void content
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 phase volume percentage. By dividing the measurement function into separate modules, the system can accurately determine flow rate by combining both measurements, resolving the contradiction between measurement accuracy and device complexity.
Solution Approach 2:
The void fraction sensor acts as an intermediary measurement device that provides the gas phase volume percentage needed to convert flow velocity into accurate flow rate. This intermediary measurement enables the calculation of true flow rate by accounting for the two-phase nature of liquid hydrogen flow.
2Measurement precision
If the distance between inner wall surfaces in the direction perpendicular to electrode surfaces is made shorter to improve capacitance measurement, then the electrode mounting portion geometry is optimized, but the pipe cross-section becomes non-circular
Solution Approach 1:
The insulating pipe has a non-circular cross-section specifically at the electrode mounting portions where the distance between inner wall surfaces perpendicular to electrode surfaces is shorter than the distance parallel to electrode surfaces. This local geometric modification optimizes the electric field distribution and capacitance measurement for void fraction detection, while the rest of the pipe maintains its functional flow characteristics.
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, thus facilitating better control and management of large volumes of liquid hydrogen.
Implementation Method 1
a capacitance-type void fraction sensor that measures capacitance using a pair of electrodes
Data Source
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.