Split Exhaust Manifold EGR for Engine Knock Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Naturally aspirated internal combustion engines face challenges in reducing engine knock and NOx emissions while maintaining efficient operation, particularly due to late intake valve closing which affects engine compression ratio and EGR flow.
Innovation Solution
Implementing a split exhaust system with a scavenge manifold to eject exhaust gas and fresh air at different times, allowing cooled EGR to be recirculated to the intake manifold, thereby reducing engine knock and NOx emissions while minimizing engine pumping work.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If late intake valve closing is used to reduce effective compression ratio and compression heating, then engine knock is reduced, but charge temperature increases due to heating from cylinder walls, cylinder head, and piston
Solution Approach 1:
The invention changes the timing parameters of valve operations. Specifically, it uses late intake valve closing (IVC) to reduce effective compression ratio and compression heating, while also implementing late exhaust valve closing (EVC) to enable charge cooling. This parameter change approach allows the system to reduce engine knock while compensating for charge temperature increase through strategic timing adjustments of valve events.
Solution Approach 2:
The invention applies preliminary cooling action by closing the exhaust valve late in the exhaust stroke, which traps cooler exhaust gases in the cylinder. This preliminary action of retaining cooler gases prepares the cylinder environment before the intake stroke, helping to offset the heating effects from cylinder walls, head, and piston that occur during late IVC operation.
2Use of energy by moving object
If late intake valve closing is used to push charge back into intake manifold and reduce pumping work, then engine pumping work is reduced, but EGR flow becomes more difficult since smaller pressure differential exists between intake and exhaust manifolds
Solution Approach 1:
The invention dynamically adjusts exhaust valve timing to optimize both pumping work and EGR flow. By implementing variable exhaust valve closing timing that occurs late in the exhaust stroke, the system creates dynamic pressure conditions that facilitate EGR flow while maintaining high intake manifold pressure. This dynamic timing adjustment allows the system to adapt to varying operating conditions and maintain optimal performance for both pumping work reduction and EGR delivery.
3Object-generated harmful factors
If EGR is used to reduce NOx emissions, then NOx production is reduced, but engine pumping work increases
Solution Approach 1:
The invention changes the timing parameters of valve operations to simultaneously achieve NOx reduction and pumping work reduction. Specifically, it uses late intake valve closing to increase intake manifold pressure (reducing pumping work) while implementing late exhaust valve closing to facilitate EGR flow (reducing NOx). This coordinated parameter change approach allows the system to achieve both benefits that were previously contradictory.
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 reduces engine propensity to knock, decreases NOx production, and lowers engine fuel consumption by optimizing intake manifold pressure and EGR delivery, even at wide open throttle conditions.
Implementation Method 1
the second portion of exhaust gas cooled by an exhaust gas cooler
Implementation Method 2
Exhaust gases may be returned to an engine's intake manifold when intake manifold pressure is lower than exhaust manifold pressure. The lower intake manifold pressure provides a motive force to draw exhaust gas from the exhaust manifold to the intake manifold.
Data Source
AI summary
Methods and systems are provided for providing exhaust gas recirculation to a naturally aspirated internal combustion engine. In one example, exhaust gas is recirculated to an engine intake via a dedicated scavenging manifold and a scavenging exhaust valve. The exhaust gas and fresh air that has not participated in combustion may be recirculated to engine cylinders even at high engine loads since the exhaust gas and fresh air is returned to the engine air intake at a pressure greater than atmospheric pressure.