Exhaust Purification System with Graded GPF Oxygen Storage
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Solution Overview
Problem
Existing exhaust gas purification systems for gasoline engines face challenges in efficiently removing NOx, hydrocarbons, carbon monoxide, and particulate matter, especially soot, while maintaining high engine performance and low carbon dioxide emissions, especially under varying operating conditions and Real Driving Emissions (RDE) scenarios, with the added complexity of achieving low pressure drop and high filtration efficiency in a compact design.
Innovation Solution
An exhaust gas purification system comprising a first three-way-catalyst (TWC1), a gasoline particulate filter (GPF) with enhanced oxygen storage capacity, and a second three-way-catalyst (TWC2), where the GPF's oxygen storage capacity is greater than TWC1's, positioned in consecutive order to optimize catalytic activity and filtration efficiency, with a platinum-group metal distribution that prioritizes TWC1 for initial high temperature operation and TWC2 for final purification, thereby maintaining engine performance and reducing residual pollutants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GPF and catalytic devices are combined to efficiently remove particles and gaseous pollutants, then filtration efficiency and catalytic activity are improved, but pressure drop increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of oxygen storage capacity within the GPF structure. The upstream region contains materials with higher oxygen storage capacity to handle rich exhaust conditions, while the downstream region has materials with lower oxygen storage capacity for lean conditions. This spatial differentiation allows the filter to maintain high filtration efficiency across varying operating conditions without requiring excessive filter media that would increase pressure drop.
Solution Approach 2:
The patent changes the parameter of oxygen storage capacity distribution along the flow direction of exhaust gas. By using different oxygen storage capacity materials in different regions (upstream vs downstream), the system adapts to changing exhaust composition during regeneration cycles, maintaining efficient particle removal while optimizing flow characteristics to minimize pressure drop penalties.
2Reliability
If more catalyst material and filtration means are required to increase filtration efficiency and catalytic activity, then pollutant removal efficiency is improved, but pressure drop increases
Solution Approach 1:
The patent implements local quality by assigning different oxygen storage capacity characteristics to different regions of the GPF. The upstream portion uses high oxygen storage capacity materials for effective soot oxidation during rich-phase regeneration, while the downstream portion uses low oxygen storage capacity materials appropriate for lean-phase operation. This regional differentiation maximizes catalytic activity where needed while minimizing unnecessary material that would increase pressure drop.
Solution Approach 2:
The patent varies the oxygen storage capacity parameter along the exhaust flow path, creating a gradient that matches the changing chemical environment during regeneration. This parameter change allows the system to achieve high catalytic activity for pollutant removal without requiring uniformly high material loading throughout the entire device, thereby controlling pressure drop.
3Temperature
If the GPF is operated close to the engine to maintain high temperature for efficient operation, then catalytic activity is improved, but the system becomes more sensitive to pressure drop affecting engine performance
Solution Approach 1:
The patent applies local quality by positioning high oxygen storage capacity materials in the upstream region of the GPF, closer to the engine, where temperatures are highest and soot oxidation demand is greatest. This localized placement ensures efficient catalytic activity at the hottest zone while the overall filter design maintains acceptable pressure drop characteristics.
Solution Approach 2:
The patent prepares the exhaust gas for efficient filtration by using the upstream high oxygen storage capacity region to pre-oxidize soot particles early in the regeneration process. This preliminary action occurs in the high-temperature zone near the engine, reducing the burden on downstream regions and allowing the system to maintain efficient operation without excessive pressure drop.
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 efficient removal of gaseous and particulate pollutants with a balanced distribution of platinum-group metals, maintaining low pressure drop and high engine performance, ensuring compliance with stringent emission standards, including EURO6, and providing effective on-board diagnosis capabilities.
Implementation Method 1
The GPF should efficiently reduce the particle mass (PM) and the particle number (PN) of the exhaust gas
Implementation Method 2
a first three-way-catalyst (TWC1), a gasoline particulate filter (GPF) and a second three-way-catalyst (TWC2)
Implementation Method 3
the oxygen storage capacity (OSC) of the GPF is greater than the OSC of the TWC1
Data Source
AI summary
An exhaust gas purification system for a gasoline engine is described the system comprising in consecutive order the following devices: •a first three-way-catalyst (TWC1), a gasoline particulate filter (GPF) and a second three-way-catalyst (TWC2), •wherein the oxygen storage capacity (OSC) of the GPF is greater than the OSC of the TWC1, wherein the OSC is determined in mg/l of the volume of the device.