Wall-flow filter with upstream storage monolith for exhaust gas
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Solution Overview
Problem
Existing exhaust-gas aftertreatment systems for internal combustion engines face challenges in optimizing the utilization of storage materials in wall-flow filters, leading to incomplete adsorption and early breakthrough of gases, which complicates regulation and diagnosis, and results in reduced efficiency and increased emissions.
Innovation Solution
A system comprising a wall-flow filter followed by a flow-through monolith, both with storage functions for compounds like NOx, SOx, NH3, and O2, where the flow-through monolith's storage capacity is designed to maximize the gradient of the breakthrough signal, ensuring optimal utilization of storage materials and improving diagnostic capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wall-flow filter with storage function is used for exhaust-gas aftertreatment, then particle removal and gas storage are achieved, but incomplete adsorption and early breakthrough of gases occur, reducing efficiency
Solution Approach 1:
The system divides the aftertreatment function into two separate units: a wall-flow filter (component 1) for particle filtration and a flow-through monolith (component 2) for gas storage. This segmentation allows each component to specialize in its optimal function, preventing the compromise seen in combined designs where particle removal and gas storage interfere with each other.
Solution Approach 2:
The flow-through monolith acts as an intermediary component between the wall-flow filter and the exhaust outlet. It receives the filtered exhaust gas and provides the additional storage capacity needed to delay breakthrough, effectively mediating the transition from incomplete adsorption to complete gas retention.
2Object-generated harmful factors
If storage capacity is increased to delay gas breakthrough, then emissions are reduced, but regulation and diagnosis become more complex
Solution Approach 1:
The system incorporates sensors that monitor the breakthrough signal and provide feedback to the control unit. This feedback mechanism allows the system to automatically adjust operation based on the actual state of the storage materials, simplifying regulation despite the increased storage capacity and providing clear diagnostic information about system status.
Solution Approach 2:
The patent replaces complex mechanical regulation mechanisms with electronic control and sensor-based monitoring. The control unit processes sensor signals and manages the aftertreatment system electronically, reducing mechanical complexity while improving diagnostic capabilities through electronic monitoring of breakthrough events.
3Measurement precision
If storage materials are optimized for complete utilization, then breakthrough signal gradient increases, but component design becomes more challenging
Solution Approach 1:
The system optimizes the storage capacity of the flow-through monolith by adjusting key parameters such as washcoat thickness, catalyst loading, and monolith geometry. These parameter changes enable complete utilization of storage materials while maintaining manufacturability, as the optimizations stay within standard manufacturing capabilities rather than requiring novel fabrication techniques.
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 enhances the utilization of storage materials, reduces emissions, and simplifies system regulation by providing a steeper breakthrough signal, allowing for more reliable compliance with emissions standards and improved diagnostic accuracy.
Implementation Method 1
both components (1) and (2) having at least one storage function for the same compound, selected from the group comprising SOx, NOx, NH3, O2, HC, H2S, which is present in the exhaust gas
Implementation Method 2
The catalytically active material which is used has the same storage functions in both units for gaseous substances present in the exhaust gas of internal combustion engines
Implementation Method 3
The harmful gases carbon monoxide and hydrocarbons can relatively easily be made non-harmful from lean exhaust gas by oxidation on a suitable oxidation catalytic converter
Implementation Method 4
The reduction of the nitrogen oxides to form nitrogen is more difficult on account of the high oxygen content in the exhaust gas of lean-burn internal combustion engines
Data Source
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AI summary
The present invention relates to an exhaust-gas aftertreatment system which comprises a catalytically active particle filter (wall-flow filter) which is followed in turn by a throughflow monolith (flow-through monolith) which is provided with a catalytically active function. The catalytically active material which is used has the same storage functions in both units for gaseous substances present in the exhaust gas of internal combustion engines. The system is suitable in particular for the simultaneous removal of particles and pollutants from the exhaust gas of both predominantly lean-operated internal combustion engines and also of internal combustion engines operated predominantly with a stoichiometric air/fuel mixture. Likewise described is the use of such a system for exhaust-gas aftertreatment.