Asymmetrical Sensor Carrier Stabilizes Flow for Mass Measurement
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Solution Overview
Problem
Conventional hot-film air-mass meters face challenges in maintaining signal quality and robustness against contamination and suffer from fluctuations in flow variables due to asymmetrical sensor carrier designs, leading to unstable wake formations and increased signal noise.
Innovation Solution
A sensor arrangement with a sensor carrier designed to have a chord length of 4.5 mm to 6.5 mm, featuring an asymmetrical outflow section and recesses, which reduces fluctuating wake and separation areas, and incorporates a printed circuit board for simplified electronics and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor carrier is designed with a conventional symmetrical shape, then the manufacturing is simpler, but the wake formation becomes unstable and signal noise increases
Solution Approach 1:
The sensor carrier is designed with an asymmetrical cross-section where the upper side (sensor chip side) has a different contour than the lower side. Specifically, the upper side features a rounded contour with a larger radius of curvature, while the lower side has a sharper contour. This asymmetry stabilizes the wake formation and reduces fluctuating separation areas, thereby decreasing signal noise and improving measurement precision.
2Measurement precision
If the sensor carrier protrudes into the measurement channel, then the sensor chip can be positioned for measurement, but flow variable fluctuations occur due to unstable wake
Solution Approach 1:
The asymmetrical cross-sectional design with a rounded upper side and sharper lower side creates more stable flow conditions. The rounded upper side promotes smoother flow separation and reduces wake fluctuations, while the sharper lower side helps anchor the flow pattern. This stabilizes the flow variables in the measurement channel while maintaining the sensor chip's positioning capability.
Solution Approach 2:
The upper side of the sensor carrier cross-section is designed with a rounded contour and larger radius of curvature. This curvature promotes smoother flow separation and reduces turbulent wake formation, thereby stabilizing flow variables and reducing signal fluctuations while allowing the sensor chip to protrude for measurement.
3Measurement precision
If the sensor carrier has a longer chord length, then the sensor chip can be better positioned, but the device complexity and production costs increase
Solution Approach 1:
The asymmetrical cross-sectional design achieves effective sensor positioning with an optimized chord length. By concentrating the rounding on the upper side and keeping the lower side sharper, the design achieves stable flow conditions and accurate sensor positioning without requiring excessive chord length, thereby controlling device complexity and production costs.
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 enhances reproducibility of characteristic curves, reduces signal noise, and improves flow uniformity, leading to more accurate and stable mass flow measurements by minimizing pulsation errors and contamination risks.
Implementation Method 1
hot-film air-mass meters are generally based on a sensor chip, in particular a silicon sensor chip, with a sensor membrane as the measuring surface or sensor area over which the flowing fluid medium can flow. As a rule, the sensor chip comprises at least one heating element and at least two temperature sensors, which are arranged, for example, on the measuring surface of the sensor chip. A mass flow and/or volume flow of the fluid medium can be inferred from an asymmetry of the temperature profile detected by the temperature sensors
Data Source
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AI summary
The invention relates to a sensor arrangement (10) for determining at least one parameter of a fluid medium flowing through a measurement channel (28), particularly of an intake air mass flow of an internal combustion engine. The sensor arrangement (10) comprises a sensor housing (12), in particular a plug-in sensor which is introduced or can be introduced into a flow tube and in which the measurement channel (28) is formed, and at least one sensor chip (42) which is arranged in the channel (28) and is intended to determine the parameter of the fluid medium. The sensor chip (42) is held in a sensor carrier (40) protruding into the measurement channel (28). The sensor carrier (40) is designed such as to have a chord (78). Said chord (78) has a length of 4.5 mm to 6.5 mm. In a preferred embodiment, the sensor carrier is shaped like a double ellipsis or a diving board.