Curved PM Sensor for Uniform Exhaust Deposition
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Solution Overview
Problem
Existing particulate matter (PM) sensors in diesel exhaust gas flows have low sensitivity due to non-uniform PM deposition on the sensor surface, with most PM accumulating at the inlet side, leading to inaccurate measurements.
Innovation Solution
A PM sensor with a curved surface and interdigitated electrodes of differing voltages, where the sample flow is directed at an acute angle to ensure uniform PM distribution and effective measurement, improving sensitivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar substrate with interdigitated electrodes is used for PM sensing, then the sensor structure is simple and easy to manufacture, but the PM deposition is non-uniform and sensitivity is low
Solution Approach 1:
The patent applies curvature to the sensor surface by using a cylindrical substrate instead of a planar one. The interdigitated electrodes are wrapped around the cylindrical surface, creating a curved geometry that exposes more electrode surface area to the exhaust flow. This curvature enables more uniform PM deposition across the electrode surfaces, improving measurement accuracy while maintaining manufacturing feasibility through standard cylindrical substrate fabrication techniques.
2Ease of operation
If the sample flow is directed perpendicular to the sensor surface, then the flow distribution is straightforward, but PM accumulates mostly at the inlet side with low uniformity
Solution Approach 1:
The cylindrical geometry of the sensor surface changes the flow dynamics compared to a planar surface. The curved surface allows the exhaust flow to wrap around and contact electrodes at multiple positions along the flow path, not just at the inlet. This geometric modification promotes more uniform PM distribution across all electrode surfaces while maintaining a straightforward perpendicular flow orientation.
3Device complexity
If only a small fraction of PM experiences electrostatic forces between electrodes, then the sensor structure remains simple, but the sensitivity of the sensor is low
Solution Approach 1:
The cylindrical substrate increases the total surface area of the interdigitated electrodes that are exposed to the exhaust flow. This geometric change allows a larger fraction of PM particles in the flow to encounter and experience electrostatic forces from the electrodes, thereby improving sensor sensitivity without adding complex structural elements or increasing 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
The solution enhances the accuracy of PM concentration measurement and soot capture, leading to improved estimation of particulate loading on filters and enhanced emissions compliance, reducing warranty costs and extending component life.
Implementation Method 1
soot particles are accumulated at or near the surface of the substrate between the electrodes
Implementation Method 2
A conduit may be formed to direct the sample flow toward the curved sensor surface in a direction that may form an acute angle with a line normal to the curved sensor surface
Data Source
AI summary
Methods and systems are provided for sensing particulate matter by a particulate matter (PM) sensor positioned upstream, or downstream, of a diesel particulate filter in an exhaust system. The PM sensor may include a curved sensor surface having interdigitated electrodes of differing voltages disposed thereon. An inlet may be disposed to capture a sample flow of exhaust from an exhaust flow from a diesel engine. A conduit may be formed to direct the sample flow toward the curved sensor surface in a direction that may form an acute angle with a line normal to the curved sensor surface.