Flow Measuring Device With Localized Passage Narrowing
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Solution Overview
Problem
Conventional air flow measuring devices face a trade-off between suppressing output fluctuations due to exfoliation or turbulence and expanding the flow-rate measuring range, particularly at low air flow rates, leading to reduced accuracy and limited measuring range.
Innovation Solution
A flow measuring device with a passage narrowing part that gradually reduces the cross-sectional area from the center to both sides in the height direction, or from one side to the other side, within the passage, to minimize turbulence and maintain high flow velocity even at low air flow rates, thereby expanding the measuring range without increasing flow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passage narrowing part is formed in the sensor locating part to suppress exfoliation or turbulence, then output fluctuation of the sensing element is limited and measurement accuracy is improved, but flow resistance and pressure loss increase and flow rate measuring range narrows
Solution Approach 1:
The passage narrowing part is localized only in the sensor locating part where the sensing element is positioned, rather than narrowing the entire bypass passage. This local narrowing suppresses turbulence and exfoliation at the sensor location to improve measurement accuracy, while maintaining a larger cross-sectional area in other parts of the passage to reduce flow resistance and preserve low flow rate measuring capability.
2Measurement precision
If the cross-sectional area of the sensor locating part is remarkably small to limit output fluctuation, then measurement accuracy is improved, but air flow velocity decreases at low air flow rates and measuring range is limited
Solution Approach 1:
The passage narrowing is applied locally only in the sensor locating part, not throughout the entire bypass passage. This allows the sensor locating part to have a small cross-sectional area that limits output fluctuation and improves measurement accuracy, while other parts of the passage maintain larger cross-sectional areas that preserve air flow velocity even at low overall air flow rates.
Solution Approach 2:
The passage narrowing part reduces the cross-sectional area in a specific dimensional region (the sensor locating part) while maintaining the overall three-dimensional flow path. This dimensional localization allows turbulence suppression at the sensor interface without proportionally reducing the total flow capacity of the passage.
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 effectively suppresses output fluctuations and measurement errors while expanding the measuring range to low air flow rates, ensuring accurate and reliable air flow measurements across a wider range of flow rates.
Implementation Method 1
minimize turbulence and maintain high flow velocity even at low air flow rates
Implementation Method 2
The flow measurement element is composed of a thin-film resistive element on a surface of the sensor chip 108
Data Source
AI summary
A flow measuring device includes a housing, a support, and a flow measurement element. The housing defines a passage therein and includes a passage narrowing part, which reduces a cross-sectional area of the passage, in a predetermined part of the passage. The support has a platy shape and is disposed along a flow direction of fluid flowing in the passage. The flow measurement element is located inside the passage narrowing part and is disposed on a surface of the support. The flow measurement element detects a flow rate of fluid flowing in the passage. The passage narrowing part has an inner wall surface that gradually reduces a width of the passage from a center side to both end sides of the passage in a height direction of the passage, which is perpendicular to a direction of the width of the passage.