NOx Purge Control for Exhaust Catalyst Recovery
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Solution Overview
Problem
The NOx occlusion capacity of NOx-occlusion-reduction-type catalysts in exhaust purification systems is not efficiently recovered, as current methods rely on predetermined NOx occlusion amounts and are influenced by engine operating states and temperatures, leading to missed opportunities for recovery.
Innovation Solution
An exhaust purification system with a NOx purge control unit that dynamically assesses engine conditions to initiate NOx purge operations based on multiple criteria, including occlusion amount, conversion efficiency, and temperature, using a combination of lean and rich control strategies to recover the NOx occlusion capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If NOx purge is performed based on predetermined NOx occlusion amount threshold, then the catalyst structure is simple and easy to control, but the recovery opportunity is lost when exhaust temperature is not suitable even if NOx occlusion amount is sufficient
Solution Approach 1:
The invention changes the control parameters from a single predetermined NOx occlusion amount threshold to multiple dynamic parameters including NOx occlusion amount, exhaust temperature, and conversion efficiency. The control unit continuously monitors these parameters and dynamically adjusts the purge timing decision, allowing the system to identify optimal recovery opportunities that consider both catalyst state and engine operating conditions.
2Ease of operation
If NOx purge is performed only when predetermined NOx occlusion amount is reached, then the control logic is simple, but recovery opportunities are missed when exhaust temperature conditions are not optimal
Solution Approach 1:
The invention implements a feedback mechanism where the control unit continuously monitors exhaust temperature, NOx occlusion amount, and conversion efficiency, then uses this feedback information to dynamically adjust the purge timing decision. This closed-loop control ensures that purge operations are initiated only when both NOx occlusion amount and temperature conditions are optimal,提高ing reliability without significantly complicating the control logic.
3Productivity
If multiple parameters (occlusion amount, conversion efficiency, temperature) are considered for purge timing, then recovery efficiency is improved, but the measurement and detection difficulty increases
Solution Approach 1:
The invention makes the control unit multi-functional by enabling it to perform multiple tasks: monitoring NOx occlusion amount, measuring exhaust temperature, calculating conversion efficiency, and making purge timing decisions. By consolidating these functions into a single control unit that processes multiple parameters simultaneously, the system improves recovery efficiency while managing measurement and detection complexity through integrated control architecture.
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 effectively recovers the NOx occlusion capacity of the NOx-occlusion-reduction-type catalyst, optimizing the recovery process by considering various engine states and conditions, thereby enhancing the efficiency of the NOx purification process.
Implementation Method 1
When the exhaust is in a lean atmosphere, the NOx-occlusion-reduction-type catalyst occludes NOx contained in the exhaust
Implementation Method 2
the NOx-occlusion-reduction-type catalyst detoxifies and releases the occluded NOx with hydrocarbon contained in the exhaust by reduction and purification
Implementation Method 3
the oxidation catalyst 31 oxidizes the same to increase an exhaust temperature
Implementation Method 4
the reduction catalyst 35 reduces NOx to nitrogen and water vapor
Data Source
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AI summary
An exhaust purification system is provided with a NOx-occlusion-reduction-type catalyst 32 that occludes NOx in exhaust when exhaust is in a lean state and reduces and purifies the occluded NOx when the exhaust is in a rich state, and a NOx purge rich control unit 140 that executes NOx purge of reducing and purifying the occluded NOx by putting the exhaust into the rich state by fuel injection control, in a case where a catalyst temperature of the NOx-occlusion-reduction-type catalyst 32 is equal to or higher than a catalyst temperature threshold value Temp_cat_std and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value STR_thr_NOx, and executes the NOx purge even when the NOx occlusion amount is less than the NOx occlusion amount threshold value STR_thr_NOx, in a case where the catalyst temperature is equal to or higher than a catalyst temperature threshold value Temp_cat_Hi which is greater than the catalyst temperature threshold value Temp_cat_std.