Gas Sensor Protective Cover Flow Channel Design
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Solution Overview
Problem
Gas sensors experience a decrease in response at low flow speeds of measurement-object gas, particularly when the flow speed is below 2 m/s, due to reduced flow rates and increased detection time, which affects the accuracy of gas concentration detection.
Innovation Solution
The gas sensor design includes a cylindrical inner protective cover with a sensor element chamber and a cylindrical outer protective cover, forming first and second gas chambers that optimize the flow channel cross-sectional areas to enhance the flow rate of measurement-object gas, with specific cross-sectional areas and ratios that facilitate easier passage of gas through the sensor element chamber inlets, reducing the impact of low flow speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flow speed of measurement-object gas is low (below 2 m/s), then the gas sensor can operate in low flow conditions, but the response of gas concentration detection decreases
Solution Approach 1:
The flow channel is segmented into multiple sections: a first flow channel section with a first cross-sectional area and a second flow channel section with a second cross-sectional area. This segmentation allows different flow characteristics in different regions, enabling the sensor to maintain good response even at low flow speeds by optimizing each section's contribution to gas delivery.
Solution Approach 2:
The patent changes the cross-sectional area parameter along the flow direction. The first cross-sectional area is set to be smaller than the second cross-sectional area, creating a gradual expansion that optimizes gas flow velocity and pressure distribution. This parameter change ensures sufficient gas delivery to the sensor element while maintaining operational adaptability across different flow conditions.
2Productivity
If the cross-sectional area of the flow channel is increased to improve gas flow rate, then the response at low flow speeds improves, but the device complexity increases
Solution Approach 1:
The protective cover integrates multiple functions: it protects the sensor element, defines the flow channel geometry, and creates the variable cross-sectional area structure. By merging these functions into a single component, the design achieves improved gas flow characteristics without proportionally increasing device complexity.
Solution Approach 2:
The first and second flow channel sections serve multiple purposes: they guide gas flow, control velocity profiles, manage pressure distribution, and deliver gas to the sensor element. This multi-functionality allows the structure to achieve high productivity without requiring additional separate components, thus limiting the increase in device complexity.
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
This configuration increases the flow rate of measurement-object gas to the sensor element chamber inlets, thereby reducing the decrease in response at low flow speeds and maintaining detection accuracy, while also minimizing heat loss and cooling of the sensor element.
Implementation Method 1
the outer protective cover and the inner protective cover form, as spaces between the outer protective cover and the inner protective cover, a first gas chamber that functions as a flow channel for the measurement-object gas between the one or more outer inlets and the one or more element chamber inlets
Data Source
AI summary
A gas sensor includes a sensor element, an inner protective cover having one or more element chamber inlets and including a first member and a second member, and an outer protective cover having one or more outer inlets. A first gas chamber between the outer protective cover and the inner protective cover has a first space and a second space. A cross-sectional area Cs that is a flow channel cross-sectional area in the second space when the measurement-object gas passes from an outside of the second member toward an inside of the second member just above the second member is greater than or equal to 14.0 mm2, and a cross-sectional area Ds that is a cross-sectional area perpendicular to a circumferential direction of the inner protective cover in the second space is greater than or equal to 0.5 mm2 and less than or equal to 6.4 mm2.