Spherical Exhaust Particulate Matter Sensor with Flow Tube Contamination Shield
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Solution Overview
Problem
Existing particulate matter sensors in exhaust systems face contamination issues due to water droplets and larger particulates, leading to reduced sensitivity and inaccurate filtration diagnosis, resulting in false indications of diesel particulate filter (DPF) degradation and unnecessary filter replacements.
Innovation Solution
A particulate matter sensor with a spherical assembly and flow tubes is positioned downstream of the DPF, featuring a sensor element distal to the flow tubes, with a hollow support rod for mounting, directing exhaust gases through a gap between concentric tubes to separate contaminants from the sensor, ensuring accurate filtration diagnosis and reduced contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor element is positioned closer to the inlet apertures to capture more incoming particulates, then the sensor sensitivity is improved, but the sensor element becomes more vulnerable to contamination by water droplets and larger particulates
Solution Approach 1:
A protective coating is applied to the sensor element to act as an intermediary layer that repels water droplets and larger particulates while allowing charged soot particles to be captured. This coating enables the sensor element to be positioned closer to the inlet apertures for improved sensitivity without direct contamination.
Solution Approach 2:
The sensor element surface properties are modified through protective coating to change its interaction with different particulate types. The coating alters surface charge distribution and hydrophobicity, enabling selective attraction of soot particles while repelling water and larger contaminants.
2Object-affected harmful factors
If additional protective coating is added to protect the sensor element from direct impingement of larger particulates and water droplets, then the sensor is protected from contamination, but the electrostatic attraction between charged soot particles and the electrodes is reduced
Solution Approach 1:
The protective coating is engineered with specific thickness and material properties to maintain adequate electrostatic attraction. By optimizing the coating parameters (thickness, composition, surface charge), the system achieves both protection from contaminants and sufficient sensitivity to detect charged soot particles.
3Ease of operation
If the sensor is mounted at the bottom of the exhaust pipe to facilitate drainage, then water condensing at the bottom can be drained, but water may overflow into the sensor element thereby contaminating it
Solution Approach 1:
The protective coating on the sensor element acts as an intermediary barrier that prevents water from penetrating to the electrodes even when water overflows into the sensor housing. This allows the sensor to be mounted in drainage-facilitated positions without compromising protection.
4Measurement precision
If the sensor element is positioned closer to the center of the exhaust pipe to represent average soot concentration, then the measurement accuracy is improved, but the sensor element is more exposed to contaminants
Solution Approach 1:
The protective coating serves as an intermediary shield that enables the sensor element to be positioned in the high-accuracy center location of the exhaust pipe while protecting it from contaminants that would otherwise be more prevalent in that position.
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 sensor reliability and accuracy, reducing false filter degradation indications and warranty costs by effectively shielding the sensor from contaminants and improving exhaust emissions compliance.
Implementation Method 1
the electrostatic attraction between the charged soot particles and the electrodes of the sensor element
Data Source
AI summary
Methods and systems are provided for a particulate matter sensor positioned downstream of a diesel particulate filter in an exhaust system. In one example, a particulate matter sensor may include a spherical assembly including a hollow rod and a plurality of flow tubes connected to diametrically opposite ends of the assembly, and a sensor element positioned within the assembly, distal to the plurality of flow tubes, thus protecting the sensor element from contaminants and water droplets condensing at or near the plurality of flow tubes. In addition, the support rod may further include a drainage hole to flow larger particulates out the spherical assembly and out into the exhaust passage.