Segmented Exhaust Filter for Low-Pressure NOx Reduction
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Solution Overview
Problem
Existing exhaust line systems for internal combustion engines face challenges in minimizing size while ensuring effective depollution of nitrogen oxides, as increased catalytic coating leads to clogged pores, increased engine fuel consumption, and high costs, particularly at low temperatures and in small vehicles with short tubing.
Innovation Solution
Incorporating an additional filter upstream of the particulate filter, impregnated with a higher quantity of catalytic coating, which creates a lower pressure drop and allows for quicker temperature rise, enabling efficient nitrogen oxide reduction without clogging the particulate filter, and using a reducing agent like urea that decomposes to ammonia, accelerated by zeolites in the additional filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quantity of catalytic coating impregnated on the walls is increased to guarantee regulatory depollution, then the depollution efficiency is improved, but the pores of the porous walls become clogged leading to increased pressure drop and fuel consumption
Solution Approach 1:
The exhaust line is divided into two separate filter units: a first filter (particulate filter) for particle filtration and a second filter (additional filter) for nitrogen oxide reduction. This segmentation allows each filter to have optimized catalytic coating quantities appropriate for its specific function, preventing pore clogging in the particulate filter while ensuring sufficient depollution capacity in the second filter.
Solution Approach 2:
The second filter acts as an intermediary component between the particulate filter and the exhaust outlet. It provides the additional catalytic coating needed for nitrogen oxide reduction without interfering with the particulate filter's pore structure, thus mediating between the need for depollution efficiency and the need to maintain low pressure drop.
2Reliability
If the volume of the particulate filter is increased to deposit more catalytic coating, then the depollution capacity is improved, but the size of the exhaust line increases
Solution Approach 1:
Instead of increasing the volume of a single particulate filter, the depollution function is segmented between two compact filters. The second filter is specifically dedicated to nitrogen oxide reduction and can be positioned upstream, allowing the particulate filter to maintain its original compact size while the system achieves enhanced overall depollution capacity.
Solution Approach 2:
The solution moves from increasing volume in one dimension to adding a new functional dimension by introducing a second filter type. This allows the system to achieve higher depollution capacity through functional differentiation rather than volumetric expansion, maintaining compact exhaust line dimensions.
3Reliability
If the quantity of catalyst is increased to maintain satisfactory nitrogen oxide reduction at low temperature, then the reduction efficiency is improved, but the manufacturing cost increases due to precious materials
Solution Approach 1:
The catalytic functions are segmented between two filters, allowing the second filter to be optimized specifically for nitrogen oxide reduction at low temperatures. This segmentation enables the use of precious metal catalysts concentrated only where needed for SCR functionality, rather than distributing them throughout the entire particulate filter structure, thereby reducing overall material costs.
Solution Approach 2:
The second filter is designed with local quality optimization for nitrogen oxide reduction, concentrating catalytic materials specifically in the region and structure where SCR reactions occur. This allows efficient low-temperature reduction without unnecessarily increasing the quantity of precious materials across the entire exhaust treatment system.
4Reliability
If the reducing agent injection point is positioned far upstream to allow urea decomposition, then the decomposition time is sufficient, but the tubing length increases for small vehicles
Solution Approach 1:
The second filter is positioned upstream in the exhaust line, performing nitrogen oxide reduction before the exhaust gases exit the system. This upstream positioning allows the filter to utilize the thermal energy already present in the exhaust gases for catalyst activation and reaction, eliminating the need for long tubing distances and enabling compact vehicle integration while maintaining effective depollution.
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 allows for increased catalytic coating without pore clogging, reduces engine fuel consumption, and enables nitrogen oxide reduction at lower temperatures, shortening the required tubing length and lowering costs.
Implementation Method 1
The internal walls of the additional filter are impregnated with a catalytic coating forming a second catalyst for reducing nitrogen oxides (NOx). It comprises an internal structure such that the additional filter creates a pressure drop lower than the pressure drop created by the same volume of particulate filter impregnated with the same quantity of same catalytic coating.
Implementation Method 2
accelerated by zeolites in the additional filter
Implementation Method 3
accelerated by zeolites in the additional filter
Implementation Method 4
enabling efficient nitrogen oxide reduction at lower temperatures
Implementation Method 5
the soot particles settle and accumulate on the porous walls of the filter
Data Source
Figure 1
AI summary
The invention relates to an exhaust line (8) of an internal combustion engine (6), comprising: - a pipe (12) receiving exhaust gases, and - a particulate filter (14) impregnated: with a first catalytic coating forming a reduction catalyst for nitrogen oxides (NOx), and with a second catalytic coating forming a first oxidation catalyst for carbon monoxide (CO) and hydrocarbons (HC), characterized in that: - the line (8) comprises an additional filter (30), housed in the pipe (12) downstream of the particulate filter (14) and impregnated with a catalytic coating forming a second reduction catalyst for nitrogen oxides (NOx), and - the additional filter (30) has an internal structure such that the additional filter (30) creates a pressure drop which is less than the pressure drop created by the same volume of particulate filter (14) impregnated with the same quantity of the same catalytic coating.