Nitrogen Oxide Trap Purge Control for Diesel Engines
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Solution Overview
Problem
Existing nitrogen oxide trap purging methods in diesel engines are prone to incomplete purges due to uncontrollable and unpredictable engine and vehicle operating conditions, leading to increased risk of premature interruption and inefficiency in NOx reduction.
Innovation Solution
A method that includes determining the current NOx mass in the trap, transitioning to a rich mixture adjustment, maintaining this adjustment as long as specific conditions are met, and implementing a standby lean mixture adjustment if the purge duration is less than a predetermined threshold, allowing for immediate resumption of purging when conditions are met again.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is switched to rich mixture for purging the nitrogen oxide trap, then the NOx stored in the trap is reduced and transformed into harmless molecules, but there is a delay of around 2s during the transient phase before the mixture reaches the desired state at the inlet of the trap
Solution Approach 1:
The control unit predisposes the engine adjustment by modifying fuel injection timing and quantity before the actual purge begins. This preliminary action reduces the transient phase duration by preparing the engine to reach the rich mixture state faster, allowing the purge to start more quickly after the decision is made.
Solution Approach 2:
The invention dynamically adjusts fuel injection parameters (timing and quantity) during the transient phase to optimize the transition to rich mixture. This dynamic control accelerates the response of the air-fuel mixture composition, reducing the delay before effective purging begins.
2Ease of operation
If the purge is interrupted when operating conditions are no longer fulfilled, then the engine can resume normal operation, but there is a risk of incomplete purge and the average time for a complete purge increases to around 10s
Solution Approach 1:
The control unit continuously monitors operating conditions (engine torque, vehicle speed, accelerator position) and uses this feedback to determine when to start, continue, or interrupt the purge. This feedback mechanism allows the system to adapt to changing conditions while maximizing purge effectiveness within available time windows.
Solution Approach 2:
The control unit identifies and prepares for purge opportunities in advance by monitoring when operating conditions are favorable. By predisposing the engine adjustment before the purge actually begins, the system maximizes the use of available time windows and reduces the impact of interruptions.
3Speed
If the engine adjustment is predisposed to maintain the trap at the correct temperature for effective purge, then the purge can start more quickly when conditions are met, but the transient adjustment phase still increases the risk of prematurely interrupted purges
Solution Approach 1:
The control unit predisposes the engine adjustment by modifying fuel injection timing and quantity before the actual purge begins. This preliminary action reduces the transient phase duration by preparing the engine to reach the rich mixture state faster, allowing the purge to start more quickly after the decision is made.
Solution Approach 2:
The invention changes key parameters of the fuel injection system (timing and quantity) to optimize the transition to rich mixture. By adjusting these parameters dynamically, the system accelerates the response of the air-fuel mixture composition, reducing the delay before effective purging begins.
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 method ensures a more complete and efficient NOx purge by minimizing the impact of transient adjustments and maintaining engine readiness for purging, reducing the risk of premature interruptions and improving NOx reduction efficiency.
Implementation Method 1
during normal engine operation in a lean mixture, it stores a more or less significant fraction of the nitrogen oxides (NOx) emitted in the combustion gases of the engine
Implementation Method 2
under the action of reducing fuel molecules sent to the engine exhaust and entering the trap, the NOx stored during the lean burn operating phase are reduced and transformed into harmless molecules
Data Source
Figure 1
Figure 2
AI summary
A nitrogen oxide trap purge is triggered when a nitrogen oxide mass threshold (200) is reached during lean-burn engine operation (100). The engine setting is switched to a rich mixture (300–500) by changing the position of the engine's air chain actuators and adding a fuel post-injection. If the purge is interrupted (900) before completion, the post-injection is suppressed, but the air chain actuator settings remain unchanged. If, within a limited time (1500), the purge conditions are met again (1300), the post-injection is added instantly, allowing the purge to resume immediately (500).