Ammonia Feed Control for Exhaust Purification Systems
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Solution Overview
Problem
In internal combustion engine exhaust purification systems, filter regeneration processing during idling or engine stop conditions requires less energy but may lead to ammonia slip due to rapid catalyst temperature rises, necessitating careful ammonia adsorption management to prevent ammonia leakage.
Innovation Solution
An exhaust purification system with a particulate filter and selective reduction catalyst, where the ammonia feed is controlled to gradually decrease adsorption levels in stages, allowing for efficient filter regeneration while minimizing ammonia slip by adjusting regeneration conditions based on engine speed and NOX discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If filter regeneration processing is performed during normal operation, then a large amount of exhaust gas passes through the particulate filter, but the energy required for maintaining the particulate filter at a high temperature becomes greater
Solution Approach 1:
The system dynamically adjusts the ammonia feed amount based on engine operating conditions (idling vs. normal operation). During idling, the ammonia feed is reduced to allow the catalyst to release adsorbed ammonia, preventing ammonia slip when the filter is heated. During normal operation, the ammonia feed is increased to maintain NOX purification performance. This dynamic adjustment resolves the contradiction by adapting the ammonia management strategy to the specific operating condition.
2Use of energy by moving object
If filter regeneration processing is performed during idling operation or while the engine is stopped, then the energy required for regeneration becomes smaller, but the selective reduction catalyst temperature rises and ammonia slip occurs
Solution Approach 1:
Before initiating filter regeneration processing during idling or engine stop, the system preliminarily reduces the ammonia feed amount. This preliminary action allows the selective reduction catalyst to release the adsorbed ammonia in advance, ensuring that when the filter is heated during regeneration, no significant ammonia slip occurs. This preemptive ammonia management resolves the contradiction between energy-efficient regeneration and ammonia slip prevention.
Solution Approach 2:
The system changes the ammonia feed parameter based on the engine operating state. During idling or engine stop conditions leading to regeneration, the ammonia feed amount is set to a reduced level. During normal operation, the ammonia feed amount is increased to maintain NOX purification. This parameter adjustment resolves the contradiction by optimizing ammonia management for each specific operating condition.
3Reliability
If the selective reduction catalyst adsorbs ammonia, then NOX purification is maintained, but during filter regeneration the catalyst cannot adsorb ammonia and ammonia slip occurs
Solution Approach 1:
The system dynamically adjusts the ammonia feed amount based on engine operating conditions. During normal operation, the ammonia feed is maintained at a level that ensures the catalyst adsorbs sufficient ammonia for NOX purification. During idling or engine stop conditions when regeneration is planned, the ammonia feed is reduced to allow the catalyst to release adsorbed ammonia, preventing ammonia slip. This dynamic control resolves the contradiction by adapting ammonia management to operational requirements.
Solution Approach 2:
The ammonia feed parameter is changed according to the engine operating state. When the engine is in normal operation mode, the ammonia feed amount is set to maintain NOX purification. When the engine is idling or stopped and filter regeneration is to be performed, the ammonia feed amount is reduced to prevent ammonia slip. This parameter adjustment strategy resolves the contradiction between maintaining NOX purification and preventing ammonia slip during regeneration.
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 ammonia slip during filter regeneration, ensuring efficient particulate filter regeneration with reduced energy consumption and controlled catalyst temperature, maintaining effective NOX purification.
Implementation Method 1
the amount of adsorption of the ammonia ingredient at the selective reduction catalyst is maintained at a suitable level
Implementation Method 2
a particulate filter which traps particulate matter (below, referred to as 'PM') in exhaust gas
Implementation Method 3
a selective reduction catalyst which reduces and purifies NOX in the exhaust gas by reduction
Implementation Method 4
a filter regeneration processing is performed in which the particulate filter is raised in temperature to remove the PM which has built up at the particulate filter
Data Source
AI summary
An exhaust purification system including a particulate filter, a selective reduction catalyst provided at a downstream side from the filter, an ammonia ingredient feed device which feeds an ammonia ingredient to the selective reduction catalyst, a control device which controls the amount of the ammonia ingredient which is adsorbed at the selective reduction catalyst to become a target adsorption amount, and a filter regeneration system which performs filter regeneration processing to remove PM which has built up on the particulate filter when an execution start condition stands. When removal of PM is demanded, so long as the execution start condition of the filter regeneration processing by the filter regeneration system does not stand, the target adsorption amount is decreased a plurality of times in stages, and the execution start condition of the filter regeneration processing is changed to a different condition at each stage of the target adsorption amount.