Dedicated EGR Cylinder Control via Differential Fueling
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Solution Overview
Problem
Engines with dedicated EGR cylinders face limitations in controlling the EGR fraction and temperature composition at the intake manifold, leading to reduced control over the system and simplified hardware configurations.
Innovation Solution
A system and method for controlling a divided exhaust engine with dedicated EGR cylinders, utilizing a controller to manage EGR flow, fuel injection, and variable displacement mechanisms to adjust EGR fraction and stroke cycles, allowing for enhanced control over EGR fraction and temperature management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard fueling and controls are applied to dedicated EGR cylinders, then the system hardware is simplified, but the EGR fraction control is limited to a fixed ratio
Solution Approach 1:
The patent applies dynamics by making the EGR fraction variable through differential fueling strategies. The system transitions from a fixed EGR fraction (determined by cylinder ratio) to a variable EGR fraction that can be dynamically adjusted by controlling fuel injection in dedicated EGR cylinders versus nominal cylinders, allowing the EGR fraction to adapt to different operating conditions while maintaining simplified hardware.
Solution Approach 2:
The patent changes the parameter of fuel injection quantity and timing between dedicated EGR cylinders and nominal cylinders. By varying the fueling strategy (e.g., differential fueling, selective fuel cut-off), the system alters the EGR fraction and temperature composition without changing hardware configuration, thus resolving the contradiction between hardware simplicity and control flexibility.
2Ease of operation
If all cylinders are operated in the same manner, then the control system is simplified, but the temperature and composition control at the intake manifold is reduced
Solution Approach 1:
The patent applies local quality by implementing different operating conditions in dedicated EGR cylinders versus nominal cylinders. Specifically, differential fueling strategies are applied locally to EGR cylinders to control the temperature and composition of exhaust gases recirculated to the intake manifold, while nominal cylinders operate under standard conditions, thus achieving temperature control without complicating the overall system operation.
Solution Approach 2:
The patent segments the cylinder population into dedicated EGR cylinders and nominal cylinders with different control strategies. This segmentation allows independent control of EGR gas temperature and composition through targeted fuel management in EGR cylinders, while maintaining simple control for the majority of nominal cylinders, thereby balancing control simplicity with temperature management capability.
3Device complexity
If dedicated EGR cylinders are used, then hardware devices are reduced, but control over the EGR system is lost
Solution Approach 1:
The patent applies self-service by using the dedicated EGR cylinders to automatically provide variable EGR fraction control through differential fueling strategies. The system leverages the existing simplified hardware configuration and uses control algorithms that exploit the differential combustion characteristics of EGR cylinders versus nominal cylinders to achieve adaptive EGR fraction control without adding complex hardware devices like variable geometry turbines or complex valve systems.
Data Source
AI summary
A system includes an internal combustion engine having a number of cylinders, with at least one of the cylinders plumbed to have a complete recycle of the exhaust gases from the cylinder. The system further includes the completely recycled cylinder having an EGR stroke cycle, and the non-recycled cylinders of the engine having an exhaust stroke cycle. The system includes the EGR stroke cycle being distinct from the exhaust stroke cycle. An amount and composition of the exhaust gases from the recycled cylinder are distinct from the amount and composition of the exhaust gases from the non-recycled cylinders, at least at certain operating conditions of the engine.