Void Fraction Sensor Geometry for Cryogenic Flow Accuracy
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Solution Overview
Problem
Existing void fraction sensors for cryogenic liquids like liquid hydrogen face challenges in accurately measuring flow rates due to the formation of voids and fluctuations in gas-to-liquid ratios, leading to reduced measurement accuracy and potential electrode breakage or safety concerns when increasing electrode size or voltage.
Innovation Solution
A void fraction sensor with an insulating pipe containing elongated through holes and electrodes positioned to minimize electrode distance, using a ceramic material with low thermal expansion and specific permittivity to enhance measurement accuracy while maintaining liquid supply, and incorporating converters to maintain cross-sectional shape consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrode size or voltage is increased to improve measurement accuracy, then measurement precision improves, but device reliability deteriorates due to increased risk of electrode breakage
Solution Approach 1:
The patent transitions from measuring capacitance in a conventional circular cross-section pipe to measuring through elongated holes with aspect ratios of 2:1 or 3:1. This dimensional change in the measurement geometry allows electrodes to be positioned closer together (reducing distance d in C=k×A/d) while maintaining adequate sensor size, thereby improving measurement precision without requiring larger electrodes or higher voltages that would compromise reliability
Solution Approach 2:
The patent changes the geometric parameters of the measurement structure by using elongated holes instead of circular cross-sections. This parameter change allows optimization of the electrode spacing and capacitance measurement geometry, achieving better measurement accuracy without increasing electrode size or operating voltage, thus avoiding the reliability issues associated with larger electrodes
2Ease of manufacture
If conventional circular cross-section pipe is used, then manufacturing simplicity is maintained, but measurement accuracy deteriorates due to suboptimal electrode positioning
Solution Approach 1:
The patent introduces elongated holes with specific aspect ratios (2:1 or 3:1) instead of using conventional circular cross-sections. This dimensional change in the hole geometry enables optimal electrode positioning that maximizes measurement accuracy while the overall pipe structure remains relatively simple to manufacture
Solution Approach 2:
The patent applies local quality by creating elongated holes with specific geometric properties (aspect ratios of 2:1 or 3:1) in specific regions of the pipe where measurement occurs. This localized geometric optimization improves measurement precision without requiring the entire pipe structure to be complex, maintaining ease of manufacture for the overall device
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 solution improves measurement accuracy of void fractions in cryogenic liquids by increasing capacitance between electrodes, reducing stress on the insulating pipe, and ensuring stable flow velocity, thereby facilitating precise flow rate determination.
Implementation Method 1
Non-Patent Document 1 has proposed an electrostatic capacitance type void fraction sensor that measures an electrostatic 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 plurality of through holes through which a liquid flows, and a plurality of electrodes located inside or on the outer surface of the insulating pipe and facing each other across the plurality of through holes. The plurality of through holes have an elongated shape having a first direction and a second direction shorter than the first direction in a cross section perpendicular to the flow direction of the liquid. The plurality of electrodes face each other across the plurality of through holes in the second direction.