Dual-Stage Diesel Particulate Filter for Low-Temperature Regeneration
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Solution Overview
Problem
Conventional diesel particulate filters face high back pressure issues due to particulate matter accumulation, leading to reduced engine efficiency and performance, and existing regeneration methods often result in excessive NO2 emissions.
Innovation Solution
A system comprising an upstream catalyzed flow-through filter and a downstream catalyzed wall-flow filter, optimizing the NO2 to particulate matter ratio to enhance passive regeneration at lower temperatures while minimizing tailpipe NO2 emissions, using a combination of filtration efficiencies and catalyst coatings to maximize soot oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wall flow diesel particulate filters are used to achieve high particulate removal efficiency, then particulate matter is effectively captured, but back pressure increases due to flow restriction and soot accumulation
Solution Approach 1:
The system divides the particulate filtration function into two separate devices: a first diesel particulate reduction device with lower filtration efficiency and a second diesel particulate reduction device with higher filtration efficiency. This segmentation allows the first device to handle the bulk of particulate matter with lower back pressure, while the second device provides high-efficiency filtration for remaining particulates, thus resolving the contradiction between high removal efficiency and low back pressure.
2Reliability
If oxidation catalyst is used to increase NO2 concentration for complete filter regeneration, then particulate matter is fully oxidized, but excessive NO2 emissions are produced
Solution Approach 1:
The system changes the concentration parameter of NO2 in the exhaust stream by using a specific configuration of oxidation catalysts in the first diesel particulate reduction device. This controlled parameter change enables sufficient NO2 for complete regeneration of the second device while limiting excessive NO2 emissions to the environment.
3Stress or pressure
If the first diesel particulate reduction device has lower filtration efficiency, then back pressure is reduced, but more particulate matter reaches the second device
Solution Approach 1:
The system segments the particulate matter reduction function across two devices, where the first device captures a portion of particulate matter at lower back pressure, and the second device captures the remaining particulates at higher efficiency. This segmentation optimizes the balance between back pressure and total particulate matter removal.
4Reliability
If high filtration efficiency is achieved in a single device, then particulate matter is effectively removed, but the device requires frequent regeneration due to rapid soot accumulation
Solution Approach 1:
The system segments the high filtration efficiency function across two devices, allowing the second device to maintain high efficiency while the first device acts as a pre-filter. This reduces the soot accumulation rate in the second device, extending the service interval between regenerations while maintaining overall high filtration efficiency.
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 system achieves a filtration efficiency of over 92% with a reduced NO2/NOx ratio, effectively reducing particulate matter and minimizing NO2 emissions, thereby improving engine performance and compliance with environmental regulations.
Implementation Method 1
One method to produce sufficient quantities of NO2 is to use an oxidation catalyst to oxidize a portion of the NO present in the exhaust stream to NO2
Implementation Method 2
The reaction of '2NO2+C═CO2+2NO' requires 8 times NO2 per unit of C in mass
Data Source
AI summary
A system for treating diesel exhaust is disclosed. The system includes a first filter including layers of filtration material positioned between layers of corrugated metallic foil. The metallic foil defines a honeycomb arrangement of longitudinal passageways from an upstream end to a downstream end and also openings for allowing exhaust to pass between adjacent longitudinal passageways of the metallic foil. The filtration material is positioned such that exhaust between the adjacent longitudinal passageways passes through the filtration material. The metallic foil also includes flow diverting structures to divert flow within the longitudinal passageways through the openings. A second filter is positioned downstream from the first filter. The second filter defines a honeycomb arrangement of longitudinal passageways. The longitudinal passages are selectively plugged adjacent upstream and downstream ends to force flow radially through walls between the longitudinal passages of the second filter.