Layered Emission Control Device for Diesel Exhaust
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Solution Overview
Problem
Existing vehicle emission control systems face challenges in achieving emissions compliance due to functional interference and spatial constraints, particularly with diesel oxidation catalysts competing with NOx catalysts and hydrocarbon traps, exacerbated by lower exhaust temperatures and stringent regulations.
Innovation Solution
A layered emission control system is implemented, comprising a first oxidizing catalyst layer for hydrocarbon oxidation, a second HC trap layer to retain hydrocarbons and protect NO oxidation, and a third NO oxidizing catalyst layer, all supported by a substrate, allowing for synergistic emission control functions within spatial constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diesel oxidation catalyst is placed upstream of a NOx catalyst to oxidize NO to NO2, then NO oxidation function is improved, but hydrocarbon and carbon monoxide oxidation function interferes with NO oxidation
Solution Approach 1:
The patent segments the emission control function into separate physical devices: a diesel oxidation catalyst for oxidizing HCs and CO, and a separate NOx catalyst for oxidizing NO to NO2. This segmentation eliminates the functional interference that occurs when both functions are combined in a single catalyst, as each catalyst can be optimized for its specific function without interference from the other reactions.
Solution Approach 2:
The patent introduces an intermediary component - a hydrocarbon trap - positioned between the diesel oxidation catalyst and the NOx catalyst. This intermediary traps hydrocarbons before they reach the NOx catalyst, preventing HC interference with the NO oxidation function while allowing the diesel oxidation catalyst to perform its oxidizing function upstream.
2Reliability
If multiple emission control devices are arranged in different configurations to meet emissions regulations, then emissions compliance is improved, but device complexity and spatial requirements increase
Solution Approach 1:
The patent merges multiple emission control functions into a single integrated device structure. The layered emission control device combines the diesel oxidation catalyst, hydrocarbon trap, and NOx catalyst in concentric layers around a central axis, allowing all three functions to be performed in one compact unit rather than requiring separate devices arranged in complex configurations.
Solution Approach 2:
The integrated emission control device performs multiple functions simultaneously: oxidizing HCs and CO in the outer layer, trapping hydrocarbons in the intermediate layer, and oxidizing NO to NO2 in the inner layer. This multi-functionality eliminates the need for separate dedicated devices for each function, reducing overall system complexity while maintaining emissions compliance.
3Volume of moving object
If emission control devices are compacted to reduce packaging volume, then spatial constraints are improved, but functional interference and temperature control difficulties increase
Solution Approach 1:
The patent employs a nested doll configuration where emission control layers are arranged concentrically around a central axis. The hydrocarbon trap is nested within the diesel oxidation catalyst layer, and the NOx catalyst is nested within the hydrocarbon trap, creating a compact nested structure that maximizes functional density while minimizing packaging volume and preventing functional interference through spatial separation.
4Productivity
If exhaust temperatures are reduced to improve combustion efficiency, then fuel efficiency is improved, but emission control device temperature control and catalytic activity become more difficult
Solution Approach 1:
The patent applies local quality by creating distinct thermal zones within the integrated device. The outer diesel oxidation catalyst layer is positioned to receive higher temperature exhaust gases first, where it performs oxidation reactions that generate heat. This locally generated heat then propagates inward to the hydrocarbon trap and NOx catalyst layers, ensuring they operate at sufficient temperatures even when overall exhaust temperatures are reduced for improved combustion 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
This configuration reduces functional interference, improves exhaust emission quality by oxidizing hydrocarbons to generate heat for particulate filters and converting NO species to NO2 for downstream capture, enhancing emissions compliance and reducing the need for additional devices.
Implementation Method 1
A first, upper layer may include a first, oxidizing catalyst, such as a diesel oxidation catalyst (DOC), for oxidizing exhaust hydrocarbons (HCs) and generating an exotherm
Implementation Method 2
A second, intermediate layer may include a HC trap for trapping exhaust HCs
Implementation Method 3
A third, lower layer may include a second, different oxidizing catalyst for oxidizing exhaust NO species to NO2 species
Data Source
AI summary
Systems and methods are provided for a layered emission control device coupled to an exhaust manifold. Various formulations may be incorporated in a plurality of layers of the device to enable various emission control functions to be grouped within spatial constraints. For example, a first layer may include a first, oxidizing catalyst, a second layer may include a HC trap, and a third layer may include a second, different oxidizing catalyst, the second layer positioned between the first and third layers. The layers may be organized to reduce functional interference and improve functional synergy between the various emission control functions.