Lean NOx Trap Partial Regeneration During Engine Shutdown
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Solution Overview
Problem
The challenge is to efficiently regenerate a lean NOx trap (LNT) catalytic converter during engine shutdown to maintain nitrogen oxide storage capacity without consuming excessive fuel, as existing methods either require additional energy or are economically wasteful.
Innovation Solution
The system regenerates only the low-temperature storage region of the LNT catalytic converter by thermal desorption or rich-mixture operation during engine shutdown, ensuring sufficient storage capacity for nitrogen oxides upon restart while minimizing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LNT catalytic converter is regenerated completely before engine shutdown, then the nitrogen oxide storage capacity is maintained, but fuel consumption increases
Solution Approach 1:
The LNT catalytic converter is divided into two distinct storage regions: low-temperature storage locations and high-temperature storage locations. This segmentation allows selective regeneration of only the low-temperature region before engine shutdown, rather than regenerating the entire converter, thereby reducing fuel consumption while maintaining sufficient nitrogen oxide storage capacity for the next cold start.
Solution Approach 2:
Instead of performing complete regeneration of the LNT catalytic converter, the invention applies partial action by regenerating only the low-temperature storage locations. This partial regeneration is sufficient to ensure adequate nitrogen oxide storage capacity for the next cold start, avoiding the excessive fuel consumption associated with full regeneration.
2Reliability
If the LNT catalytic converter is operated at high temperature for regeneration, then the nitrogen oxides are effectively reduced, but the risk of degradation and unwanted secondary reactions increases
Solution Approach 1:
The invention changes the temperature parameter by which storage locations are differentiated into low-temperature and high-temperature regions. By targeting regeneration at lower temperatures (suitable for low-temperature storage locations), the process achieves effective nitrogen oxides reduction while avoiding the harmful effects of excessive heat such as degradation and unwanted secondary reactions.
Solution Approach 2:
Different regions of the LNT catalytic converter are assigned different thermal characteristics: low-temperature storage locations and high-temperature storage locations. This local quality differentiation allows the regeneration process to be tailored to specific regions, applying appropriate temperature conditions to each type of storage location and thereby avoiding degradation while maintaining reduction efficiency.
3Object-generated harmful factors
If the LNT catalytic converter stores nitrogen oxides during lean-mixture operation, then emissions are reduced, but the storage capacity is limited and requires periodic regeneration
Solution Approach 1:
The storage capacity is segmented into low-temperature storage locations and high-temperature storage locations, each optimized for different operating conditions. This segmentation allows the system to maintain nitrogen oxide storage capacity across a broader range of temperatures and operating conditions, effectively extending the functional storage capacity without requiring complete regeneration cycles.
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 approach reduces fuel consumption and maintains nitrogen oxide storage capacity, allowing for compliance with emissions limits by selectively regenerating only the low-temperature storage region of the LNT catalytic converter.
Implementation Method 1
The operation of an LNT catalytic converter is based on temporary storage of the nitrogen oxides during a lean-mixture operating mode of the internal combustion engine
Implementation Method 2
For regeneration, the internal combustion engine can be operated with a rich air-fuel mixture for a period of a few seconds
Implementation Method 3
The reducing components contained in this substoichiometric exhaust gas mixture react with stored nitrogen oxides, thus ideally converting the nitrogen oxides to inert nitrogen gas
Implementation Method 4
The operation of SCR catalytic converters is based on continuous reduction of nitrogen oxides via ammonia, which can be obtained from an aqueous urea solution for example
Data Source
AI summary
Methods and systems are provided for partially regenerating a lean Nox trap in response to an engine shutdown request. In one example, an engine shutdown is delayed so that a low-temperature storing region of the lean Nox trap is regenerated without regenerating a high-temperature storing region of the lean Nox trap.