Cam-Driven Fuel Pump for Dedicated EGR Cylinder Imbalance
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Solution Overview
Problem
Dedicated EGR engines face issues with cylinder-to-cylinder fuel delivery imbalance and inconsistent fueling due to the use of a common fuel rail, leading to increased emissions, poor combustion, and reduced efficiency, particularly when one or more cylinders operate in a rich combustion mode.
Innovation Solution
The implementation of a modified cam-driven fuel pump system that increases fuel delivery for dedicated EGR cylinders while maintaining consistent fuel pressure in the common rail, using cams with modified lobes to adjust the fuel pump displacement and injector pulse width, ensuring equal fuel injection across all cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common fuel rail is used for all cylinders, then the fuel system complexity is reduced, but cylinder-to-cylinder fuel delivery imbalance occurs when dedicated EGR cylinders operate in rich combustion mode
Solution Approach 1:
The patent applies local quality by modifying the cam profile specifically for the dedicated EGR cylinder fuel pump lobes to provide different fuel delivery characteristics. The cam has varying lobe profiles where lobes corresponding to dedicated EGR cylinders are designed with different displacement characteristics compared to lobes for non-dedicated cylinders, allowing localized fuel delivery optimization without changing the overall common rail system architecture.
2Reliability
If dedicated EGR cylinders operate at higher equivalence ratios (richer combustion), then knock resistance and dilution tolerance improve, but fuel pressure reduction and unwanted pressure oscillations occur in the common fuel rail
Solution Approach 1:
The patent applies dynamics by using a cam-driven fuel pump system where the cam profile is specifically designed to dynamically adjust fuel delivery timing and quantity. The varying lobe profiles on the cam allow the fuel pump to deliver fuel in a dynamic manner that compensates for pressure oscillations, maintaining stable fuel rail pressure even when dedicated EGR cylinders operate at higher equivalence ratios with increased fuel injection demands.
3Quantity of substance
If longer injector pulse width is used for dedicated EGR cylinders to achieve rich combustion, then hydrogen and carbon monoxide production increases, but fuel delivery imbalance and emission increases occur
Solution Approach 1:
The patent applies parameter changes by modifying the cam profile parameters (lobe shape, displacement, timing) to optimize fuel delivery to dedicated EGR cylinders. This allows precise control of the equivalence ratio in dedicated EGR cylinders, ensuring they operate in the optimal rich combustion range (equivalence ratio 1.0-2.0) to maximize hydrogen and carbon monoxide production for EGR benefits while preventing excessive fueling that would lead to harmful emissions and combustion instability.
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 solution achieves more consistent fuel delivery and reduced emissions by minimizing cylinder-to-cylinder fuel discrepancies, improving combustion stability and engine efficiency, and allowing for higher over-fueling tolerance without requiring separate fuel systems or additional hardware.
Implementation Method 1
a cam-driven fuel pump system that increases fuel delivery for dedicated EGR cylinders while maintaining consistent fuel pressure in the common rail, using cams with modified lobes to adjust the fuel pump displacement
Implementation Method 2
injector pulse width, ensuring equal fuel injection across all cylinders
Data Source
AI summary
A method of improving fuel delivery in an engine having one or more cylinders that are over-fueled related to other cylinders, such as a D-EGR engine. The fueling system uses a mechanical fuel pump, which is cam-driven. The cam has lobes corresponding to the desired displacement for each cylinder. The lobe corresponding to the over-fueled cylinder is shaped differently, such that the filling stroke of the pump is increased.