Soot Sensor Shield for Homogeneous Particle Deposition
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Solution Overview
Problem
Existing soot sensors in internal combustion engines face challenges with thermal and mechanical stresses, as well as difficulties in regeneration and homogeneous soot deposition, leading to inaccurate measurements and sensor integrity issues.
Innovation Solution
A soot sensor with a protective shield that diverts the gas flow upstream, creating a turbulent flow and reducing speed downstream to select particles by size, ensuring mechanical protection and homogeneous soot deposition on a planar probe with electrodes and a regeneration resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor is placed directly in the exhaust flow to measure soot concentration, then the measurement capability is improved, but the sensor is subjected to high thermal and mechanical stresses that compromise its integrity
Solution Approach 1:
A protective shield is introduced as an intermediary element between the exhaust flow and the planar probe. The shield completely covers the probe while including an open window positioned downstream that allows soot particles to reach the collection area without exposing the probe to direct frontal impact from debris and high-velocity gas flow.
Solution Approach 2:
The protective shield is segmented with a specific open window configuration that separates the functions of protection and particle collection. The window is positioned downstream of the probe to allow turbulent flow development while still enabling soot deposition on the collection area.
2Speed
If the gas flow velocity is high in the exhaust stream, then the sensor can withstand the flow conditions, but the soot deposition on the sensor becomes inhomogeneous affecting measurement accuracy
Solution Approach 1:
The protective shield is designed to create preliminary turbulent flow conditions upstream of the collection area. This turbulent flow development occurs before the gas reaches the probe, allowing the flow to slow down and redistribute particles uniformly before deposition occurs on the collection area.
Solution Approach 2:
The open window is strategically positioned downstream of the probe to create a specific local flow condition where turbulent mixing occurs before particles reach the collection area. This localized flow modification ensures homogeneous deposition only at the collection area while maintaining high flow velocity elsewhere.
3Quantity of substance
If the sensor collects all particles in the exhaust flow, then the measurement covers all soot sizes, but large agglomerates cause mechanical stress and inaccurate readings
Solution Approach 1:
The protective shield with its downstream-positioned open window creates a flow condition where only fine particles (less than 500 nm) can effectively reach the collection area through turbulent diffusion and reduced momentum. Larger agglomerates are excluded by the flow dynamics, preventing mechanical stress while still enabling measurement of the relevant fine soot fraction.
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 enables precise and reproducible soot concentration measurement, enhancing sensor robustness, reducing mechanical stress, and facilitating regeneration, while favoring the collection of fine particles and minimizing the impact of agglomerates.
Implementation Method 1
The gas flow is diverted upstream of the planar probe by means of a protective shield completely covering the planar probe and comprising an open window for collecting soot formed in a surface of the shield of protection located downstream of the planar probe in the gas flow, so as to: protect the probe from the direct frontal gas flow of soot and any debris contained in the gas flow, generate a turbulent flow and reduce the speed of the gas flow downstream of the planar probe to select the particles according to their size
Implementation Method 2
This operation is carried out by means of a heating resistor intended to burn the soot deposited between the electrodes by heating the surface of the sensor and the soot, thus making it possible to regenerate the sensor for new measurement cycles
Implementation Method 3
These sensors are in particular sensors of the resistive type comprising two conductive electrodes separated from each other and between which is measured the variation in electrical resistance with the progressive fouling of the sensor, following the deposition of soot between said electrodes
Data Source
Figure 1~4
Figure 5A~7
Figure 6A~6D
AI summary
The present invention concerns a method and a sensor (1) for collecting soot particles in an exhaust flow from an internal combustion engine, via a resistive-type planar probe positioned in the gas flow and comprising at least one surface provided with electrodes connected to an electronic device for measuring the concentration of soot particles in the gas flow. The gas flow is diverted upstream from the planar probe by a protective shield (3) completely covering the planar probe and comprising a soot particle collection window (5) formed in a wall of the protective shield (3) located downstream from the planar probe in the gas flow, in such a way as to: -protect the planar probe from a direct frontal impact of soot particles and any debris contained in the gas flow, and -generate a turbulent flow and reduce the speed of the gas flow downstream from the planar probe to select the soot particles depending on their size.