Exhaust Purification System with NOx Reduction Estimation
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Solution Overview
Problem
The NOx purge process in NOx occlusion reduction type catalysts is often ineffective when the catalyst temperature is below the activation temperature, leading to wasted fuel consumption due to unnecessary NOx purge operations.
Innovation Solution
An exhaust purification system that includes an NOx occlusion reduction type catalyst, a catalyst regeneration unit, a reduction amount estimating unit, and a prohibition unit, which estimates the NOx reduction amount before the catalyst regeneration process and prohibits the process if the estimated reduction amount is below a predetermined threshold, ensuring that the NOx purge is only executed when beneficial.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NOx purge is executed regularly to recover NOx occlusion capacity, then NOx reduction performance is improved, but fuel consumption deteriorates due to wasted post injection or exhaust pipe injection when catalyst temperature is below activation temperature
Solution Approach 1:
The system performs preliminary assessment of catalyst temperature and NOx occlusion amount before executing NOx purge. By checking whether the catalyst temperature is above the activation temperature threshold and whether the NOx occlusion amount exceeds the threshold value, the system determines in advance whether NOx purge will be effective, thereby avoiding unnecessary fuel injection and preventing fuel consumption deterioration while ensuring NOx reduction performance is maintained when conditions are appropriate
2Reliability
If NOx purge is executed when catalyst temperature is low, then NOx occlusion capacity recovery is attempted, but the NOx reduction amount is insufficient and the purge operation becomes useless
Solution Approach 1:
The system continuously monitors catalyst temperature and NOx occlusion amount, using this feedback information to determine whether to execute NOx purge. The control unit compares the current catalyst temperature against the activation temperature threshold and the NOx occlusion amount against the threshold value, making informed decisions about purge execution. This feedback mechanism ensures that NOx purge is only performed when both temperature and occlusion amount conditions indicate that the operation will be effective, thereby avoiding useless purge operations
3Reliability
If post injection or exhaust pipe injection is performed to create rich atmosphere for NOx purge, then NOx is reduced and purified, but fuel is wasted when the catalyst cannot effectively reduce NOx due to low temperature
Solution Approach 1:
The system performs preliminary verification of catalyst temperature before initiating post injection or exhaust pipe injection for NOx purge. By checking whether the catalyst temperature is above the activation temperature threshold, the system ensures that the catalyst is in a state capable of effectively reducing NOx. This preliminary action prevents fuel waste by avoiding rich atmosphere creation when the catalyst cannot perform the reduction function, while still enabling effective NOx purification when temperature conditions are satisfied
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 suppresses unnecessary NOx purge operations, thereby preventing fuel consumption deterioration and optimizing the NOx reduction process.
Implementation Method 1
When the exhaust gas is under a lean atmosphere, the NOx occlusion reduction type catalyst occludes the NOx contained in the exhaust gas
Implementation Method 2
When the exhaust gas is under a rich atmosphere, the NOx occlusion reduction type catalyst detoxifies the occluded NOx through reducing and purifying with hydrocarbon contained in the exhaust gas
Data Source
AI summary
Provided is an exhaust purification system including: an NOx occlusion reduction type catalyst that is provided in an exhaust system of an internal combustion engine, and occludes NOx when an exhaust gas is in a lean state, and reduces the NOx when the exhaust gas is in a rich state; a regeneration control unit that executes a regeneration process of bringing the exhaust gas into a rich state to reduce the NOx occluded in the NOx occlusion reduction type catalyst; a storing unit that stores an exhaust lambda prediction value in advance when the regeneration process is executed; a reduction amount estimating unit that estimates an NOx reduction amount when the regeneration process is executed; and a prohibition unit that prohibits the execution of the regeneration process by the regeneration control unit when the estimated NOx reduction amount is less than a predetermined lower limit threshold.