EGR Control via Differential Cylinder Fuel Injection
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Solution Overview
Problem
The exhaust gas recirculation (EGR) system in engines experiences significant latency, making it difficult to deliver the desired amount of EGR during changing engine operating conditions, leading to undershoots in intake oxygen concentration and degraded emissions.
Innovation Solution
A system with a controller that adjusts exhaust valves and fuel injection amounts differently between a first cylinder group (donor cylinders) and a second cylinder group (non-donor cylinders) to maintain a target intake oxygen concentration, using the exhaust valves as the primary mechanism and adjusting fuel supply to the donor cylinders to prevent intake oxygen concentration undershoots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a valve is used to control EGR flow rate, then EGR amount can be regulated, but significant latency prevents timely delivery of desired EGR during changing engine operating conditions
Solution Approach 1:
The system performs preliminary action by adjusting fuel injection amounts in advance before EGR valve adjustments take effect. The controller modifies fuel injection to donor cylinders to preemptively compensate for the latency in EGR valve response, ensuring that the desired intake oxygen concentration is maintained without undershoot during transient operating conditions.
Solution Approach 2:
The system changes parameters by adjusting fuel injection amounts in addition to EGR valve position. By modifying the fuel injection parameter to donor cylinders, the system creates a secondary control mechanism that responds faster than the EGR valve alone, compensating for the latency in the primary EGR control parameter.
2Manufacturing precision
If EGR valve position is adjusted to meet target EGR amount, then desired EGR flow is achieved, but intake oxygen concentration undershoots occur during transient conditions
Solution Approach 1:
The system applies preliminary anti-action by adjusting fuel injection amounts in the opposite direction of the EGR change before the EGR valve fully responds. When EGR is increased, fuel injection is reduced in advance to prevent oxygen concentration undershoot, counteracting the delayed effect of the EGR valve adjustment.
Solution Approach 2:
The system uses feedback by continuously monitoring intake oxygen concentration and using this information to adjust both EGR valve position and fuel injection amounts. The controller integrates feedback from oxygen concentration sensors to dynamically coordinate both control actions, ensuring that the combined effect maintains stable intake oxygen concentration during transient operations.
3Reliability
If fuel injection to first cylinder group is adjusted differently than second cylinder group, then intake oxygen concentration is maintained, but control system complexity increases
Solution Approach 1:
The system applies segmentation by dividing the cylinder groups into donor cylinders (first group) and non-donor cylinders (second group) with different control strategies. The controller independently adjusts fuel injection to donor cylinders that are connected to the EGR system, while maintaining different or equal fuel injection to non-donor cylinders, allowing targeted control that simplifies the overall control logic compared to uniform control of all cylinders.
Data Source
AI summary
Various methods and systems are provided for controlling exhaust gas recirculation in an engine. One embodiment for a system comprises an engine having first and second cylinder groups, and an exhaust gas recirculation (EGR) passage coupled between the first cylinder group and an intake manifold of the engine, flow of EGR through the EGR passage controlled by one or more EGR exhaust valves, and a controller configured to maintain a target intake gas concentration by adjusting the one or more EGR exhaust valves and adjusting fuel injection amounts to the first cylinder group differently than the second cylinder group.