Gasoline TWC1-GPF-TWC2 Exhaust Purification for Dynamic RDE
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Solution Overview
Problem
Existing exhaust gas purification systems for stoichiometrically operated internal combustion engines struggle to meet stringent Euro 6d RDE standards, particularly in dynamic conditions, and fail to efficiently convert hydrocarbons, nitrogen oxides, and secondary pollutants like NH3 and N2O, while maintaining low fuel consumption.
Innovation Solution
An exhaust system comprising a TWC1 on a flow-through substrate, followed by a GPF, and a downstream TWC2, with additional materials for temporarily storing hydrocarbons, utilizing zeolites or zeolite-like compounds with transition metals, enhances pollutant conversion and storage capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional TWC system is used for stoichiometric engines, then the basic purification of hydrocarbons, CO and NOx is achieved, but the system cannot meet stringent Euro 6d RDE standards under dynamic conditions and fails to efficiently convert secondary pollutants like NH3 and N2O
Solution Approach 1:
The exhaust purification system is divided into multiple functional segments: TWC1 for basic three-way conversion, GPF for particle filtration, TWC2 for additional purification, and HCT for hydrocarbon storage. Each segment handles specific pollutants or functions, allowing the system to meet stringent Euro 6d RDE standards under dynamic conditions while maintaining high purification efficiency for both primary and secondary pollutants.
2Reliability
If hydrocarbon storage materials are added to the exhaust system, then the system can temporarily store and subsequently convert hydrocarbons improving cold start performance, but the storage materials are exposed to high temperatures that could cause thermal damage
Solution Approach 1:
The hydrocarbon storage material is nested within the porous structure of the catalyst substrate. The porous walls provide thermal protection to the storage material while allowing hydrocarbon molecules to diffuse in and out. This nested configuration allows the HCT to improve cold start performance by storing hydrocarbons during cold operation and releasing them for conversion during warm operation, while the catalyst substrate shields the storage material from direct thermal exposure.
Solution Approach 2:
The porous catalyst substrate acts as an intermediary between the hot exhaust gas and the hydrocarbon storage material. It allows hydrocarbon molecules to pass through while providing thermal insulation, protecting the storage material from direct thermal damage. The substrate mediates the interaction between the thermal environment and the storage material, enabling the HCT to function effectively without suffering from thermal degradation.
3Reliability
If the exhaust system is designed with multiple components (TWC1, GPF, TWC2, HCT) to meet future standards, then purification capability is enhanced, but the system complexity and fuel consumption increase
Solution Approach 1:
The GPF substrate serves multiple functions: it acts as the particle filter structure, provides the porous matrix for hydrocarbon storage material, and offers thermal protection. The HCT integrates with the catalyst substrate rather than being a separate component, reducing overall system complexity while maintaining enhanced purification capability for meeting future emission standards.
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 effectively reduces hydrocarbons, nitrogen oxides, and secondary pollutants, meeting future exhaust gas standards while minimizing fuel consumption and preventing thermal damage to storage materials.
Implementation Method 1
three-way catalysts (TWC). Such catalysts are capable of simultaneously converting the three major gaseous pollutants of the engine, namely hydrocarbons, carbon monoxide and nitrogen oxides, into harmless components
Implementation Method 2
oxygen storage materials, e.g., cerium/zirconium mixed oxides. In the latter case, cerium oxide, a rare earth metal oxide, constitutes the component that is fundamental to the oxygen storage
Implementation Method 3
The channels are alternately closed at one of the two ends of the filter so that channels A, which are open at the first side of the filter and closed at the second side of the filter, and channels B, which are closed at the first side of the filter and open at the second side of the filter, are formed. For example, exhaust gas flowing into channels A can only leave the filter via channels B and must flow through the porous walls between channels A and B for this purpose. When the exhaust gas passes through the wall, the particles are retained and the exhaust gas is cleaned.
Implementation Method 4
the wall-flow filter can, for example, be provided with catalytically active coatings that reduce the ignition temperature of soot. Applying such coatings to the porous walls between the channels (so-called on-wall coating) or introducing them into the porous walls (so-called in-wall coating) is already known.
Implementation Method 5
utilizing zeolites or zeolite-like compounds with transition metals, enhances pollutant conversion and storage capabilities
Data Source
AI summary
The invention is directed to the purification of exhaust gases of an internal combustion engine operated predominantly with a stoichiometric fuel mixture. The exhaust gas system has in particular 4 purification functions in a particular order. A three-way catalyst (TWC1) near the engine is followed by a gasoline particle filter (GPF) and another three-way catalyst (TWC2) downstream thereof. The system additionally includes a hydrocarbon storage function.