Dynamic NOx Purge Threshold for Catalyst Deterioration
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Solution Overview
Problem
The NOx storage capacity of catalysts in exhaust gas purification systems deteriorates over time or due to heat, leading to ineffective NOx purges and worsening exhaust emissions when a fixed storage amount threshold is used.
Innovation Solution
An exhaust gas purification system that adjusts the NOx storage amount threshold and NOx purge interval based on the degree of catalyst deterioration, using sensors and control units to monitor and correct these parameters dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed storage amount threshold is used for NOx purge, then the system is simple to operate, but the NOx purge cannot be started effectively when catalyst deterioration occurs
Solution Approach 1:
The storage amount threshold is changed from a fixed value to a dynamic value that automatically adjusts based on catalyst deterioration degree. The ECU corrects the threshold downward as deterioration increases, ensuring the purge is triggered at appropriate moments throughout the catalyst's lifecycle without requiring manual intervention or complex external systems.
Solution Approach 2:
The system implements feedback by continuously monitoring catalyst deterioration degree (through mileage, temperature history, and performance parameters) and using this information to automatically adjust the storage amount threshold. This closed-loop approach ensures the purge timing adapts to actual catalyst condition, maintaining reliability while keeping the control mechanism integrated within the existing ECU.
2Reliability
If the storage amount threshold is set high, then NOx storage capacity is maintained, but purge timing is delayed causing emissions to worsen with catalyst deterioration
Solution Approach 1:
The system changes the threshold parameter dynamically based on catalyst deterioration. Initially, when the catalyst is new, a higher threshold allows maximum NOx storage. As deterioration progresses (tracked via mileage and temperature history), the threshold is progressively lowered, ensuring purges occur sooner to prevent emission deterioration, thus adapting the timing parameter to the catalyst's actual state.
3Reliability
If frequent purges are performed, then NOx storage capacity is maintained, but fuel consumption increases
Solution Approach 1:
The purge frequency is made dynamic rather than fixed. The system performs purges only when the storage amount reaches the dynamically adjusted threshold, which is higher when the catalyst is healthy and lower when deteriorated. This adaptive approach ensures purges are performed at the minimum necessary frequency to maintain effective NOx control, avoiding unnecessary fuel consumption while preventing emission deterioration.
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
Prevents the worsening of exhaust emissions by ensuring timely and effective NOx purges according to the catalyst's condition, maintaining emission control and reducing the risk of hydrocarbon slip.
Implementation Method 1
The NOx storage-reduction catalyst stores NOx contained in exhaust gas when the exhaust gas is in a lean atmosphere
Implementation Method 2
reduces and purifies the NOx that is stored therein with hydrocarbons contained in the exhaust gas when the exhaust gas is in a rich atmosphere
Data Source
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AI summary
There is provided an exhaust gas purification system including: a NOx storage-reduction catalyst 32 that is provided in an exhaust system of an internal combustion engine 10 to reduce and purify NOx in exhaust gas; a deterioration degree estimation module 120 for estimating a degree of deterioration of the NOx storage-reduction catalyst 32; a NOx storage amount estimation module 113 for estimating a NOx storage amount of the NOx storage-reduction catalyst 32; a regeneration control unit 100 for starting a regeneration process in which a NOx storage capacity of the NOx storage-reduction catalyst 32 is restored when a NOx storage amount that is estimated by the NOx storage amount estimation module 113 reaches a predetermined storage amount threshold; and a storage amount threshold correction module 115 for correcting the storage amount threshold based on the degree of deterioration that is estimated by the deterioration degree estimation module 120.