Capacitive Gas Sensor for Two-Phase Flow
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Solution Overview
Problem
Existing gas content measurement systems for engine supply lines, particularly in spacecraft or aircraft engines, face challenges due to large sensor dimensions, complex multiplexed output signals, and pressure drops caused by electrodes within the flow, making them unsuitable for small pipes and inefficient.
Innovation Solution
A capacitive sensor system with an insulating sheath and electrodes configured to measure capacitance variations in a two-phase flow, where the upstream and downstream pipes have identical internal sections, and the electrodes are connected to the pipe's electrical ground, reducing pressure drops and allowing for precise gas content measurement without multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrodes are positioned within the flow to measure gas content, then measurement capability is achieved, but pressure drops increase
Solution Approach 1:
The measurement system is extracted from the flow path by integrating electrodes into the pipe wall structure rather than positioning them within the flow. This allows capacitance measurements to be performed through the pipe wall, eliminating the need for electrodes to protrude into the fluid stream and thus avoiding the pressure drops they would cause.
Solution Approach 2:
The pipe wall itself serves as an intermediary medium between the electrodes and the flowing fluid. By measuring capacitance through the pipe wall material, the system can detect gas content variations in the fluid without direct electrode-fluid contact, thereby eliminating the harmful pressure drop effect while maintaining measurement capability.
2Measurement precision
If large dimension sensors are used for gas content measurement, then measurement accuracy is achieved, but adaptability to small pipes is reduced
Solution Approach 1:
The sensor design integrates measurement electrodes directly into the pipe wall structure, creating a universal measurement system that can be adapted to pipes of various diameters. The same basic electrode configuration and measurement principle can be applied to different pipe sizes by simply adjusting the electrode dimensions and spacing to match the specific pipe geometry, eliminating the need for large, fixed-dimension sensors.
3Loss of information
If multiplexed output signals are used, then comprehensive data is obtained, but signal analysis complexity increases
Solution Approach 1:
Instead of using a single multiplexed electrode that requires complex signal demultiplexing and analysis, the system employs multiple simple electrodes positioned at different locations along the pipe. Each electrode provides an independent, simple capacitance measurement signal. This segmentation of the measurement function into multiple simple channels eliminates the need for multiplexing complexity while still providing comprehensive data about gas content distribution along the pipe.
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 system enables accurate gas content measurement in two-phase flows without generating pressure drops, is adaptable to various pipe sizes, and simplifies data acquisition by using the pipe's electrical ground as a reference, improving sensitivity and reducing interference.
Implementation Method 1
the measurement electrode being configured so as to measure, with respect to the upstream ground, the capacitance and the variation capacity of the medium constituting the two-phase flow
Implementation Method 2
the guard electrode being configured so as to be subjected to the same potential as the measurement electrode
Data Source
Figure 1~3
Figure 2
AI summary
Assembly comprising an upstream conduit, a downstream conduit, and a system (1) for measuring the variation of gas content of a two-phase flow, comprising an insulating sheath (6), an upstream earth (2), a measuring electrode (3), a guard electrode (7) and a downstream earth (4) which are disposed successively in said insulating sheath (6), and each exhibiting an identical internal cross section defining an internal duct for the flow of a two-phase from the upstream earth (2) to the downstream earth (4) in the extension of the upstream conduit and of the downstream conduit, the guard electrode (7) being subjected to one and the same potential as the measuring electrode (3), the measuring electrode (3) measuring with respect to the upstream earth (2), the capacitance and the variation in capacitance of the two-phase flow, the upstream earth (2) and the downstream earth (4) being linked electrically to the upstream conduit and to the downstream conduit respectively.