Interdigitated PM Sensor with Flow Guides for Uniform Soot Deposition
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Solution Overview
Problem
Existing particulate matter (PM) sensors in exhaust gas flows have low sensitivity due to non-uniform PM deposition on their surfaces, resulting from biased flow distribution and limited surface area coverage, which affects the accuracy of PM loading estimation in diesel particulate filters.
Innovation Solution
Incorporating a pair of planar interdigitated electrodes with protruding flow guides, where evenly spaced blocks between the electrodes' tines create multiple soot bridge pathways, ensuring uniform distribution and increased surface area coverage, thereby enhancing the accuracy of PM sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional PM sensor with planar electrodes is used, then the sensor structure is simple, but the PM deposition is non-uniform and sensitivity is low
Solution Approach 1:
The sensor surface is segmented into multiple regions by adding flow guides that divide the exhaust flow into separate streams. This segmentation creates multiple independent deposition zones between electrode pairs, allowing uniform PM distribution across the sensor surface while maintaining a relatively simple overall structure.
Solution Approach 2:
Flow guides are introduced as intermediary elements between the exhaust flow and the electrode surface. These flow guides mediate the flow distribution, directing exhaust streams uniformly across multiple electrode pairs and preventing direct, uncontrolled deposition on the electrode surface, thereby improving measurement precision without excessive complexity.
2Quantity of substance
If the sensor surface area is increased to improve PM collection, then more PM can be accumulated, but the flow distribution bias worsens and deposition becomes less uniform
Solution Approach 1:
The increased sensor surface area is segmented into multiple independent deposition regions by flow guides. Each region between electrode pairs receives a controlled, uniform portion of the exhaust flow, ensuring that while total PM accumulation increases, the deposition remains uniform across all regions.
Solution Approach 2:
The problem is solved by adding a spatial dimension through flow guides that distribute flow across the width of the sensor surface. This creates a two-dimensional flow distribution pattern that ensures uniform PM deposition across the entire sensor area, allowing increased PM collection without sacrificing uniformity.
3Manufacturing precision
If flow guides are added to improve PM distribution uniformity, then deposition becomes more uniform, but the sensor complexity increases
Solution Approach 1:
The sensor is segmented into multiple flow paths using simple flow guide structures. These flow guides create distinct, uniform flow streams between electrode pairs, achieving uniform PM deposition through a relatively simple geometric modification rather than a complex control system.
Solution Approach 2:
The flow distribution parameter is changed by introducing flow guides with specific geometric parameters (spacing, height, orientation). By optimizing these parameters, uniform PM deposition is achieved through passive flow management, improving manufacturing precision without requiring active control systems or excessive structural 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 leads to more accurate PM loading estimation and improved exhaust emissions compliance, reducing warranty costs and extending exhaust component life by ensuring uniform soot distribution across the sensor surface.
Implementation Method 1
the measured conductivity provides a measure of soot accumulation
Implementation Method 2
dividing incoming PM streams in the exhaust flow into multiple PM streams at multiple flow guides
Implementation Method 3
sense a particulate matter or soot load based on a correlation between a measured change in electrical conductivity
Data Source
AI summary
Methods and systems are provided for sensing particulate matter by a particulate matter (PM) sensor positioned downstream of a diesel particulate filter in an exhaust system. In one example, a PM sensor may include a pair of protruding interdigitated electrodes on a surface of the sensor and further include a plurality of flow guides also protruding from the surface of the sensor. By staggering the flow guides across the interdigitated electrodes, soot may be accumulated across multiple pathways and thereby, soot may be accumulated uniformly across the sensor surface.