Piston Combustion Bowl Chamfer Limits Fuel Deflection
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Solution Overview
Problem
Current internal combustion engine piston designs struggle to reduce particulate matter emissions without compromising efficiency, as the science of combustion bowl and rim geometry is not fully understood, leading to unpredictable results and lengthy research and development processes.
Innovation Solution
A piston design featuring a convex inner bowl surface and concave outer bowl surface forming a combustion bowl with a 7:1 diameter-to-depth ratio, an annular piston rim with a chamfered inner rim surface sloping at 9° to 11°, which limits fuel deflection towards the cylinder bore wall, and a fuel injection strategy that autoignites fuel after the piston has passed the top dead center position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional piston designs are used, then engine efficiency is maintained, but particulate matter emissions increase
Solution Approach 1:
The piston crown incorporates a combustion bowl with specific local geometric features (7:1 diameter-to-depth ratio, non-reentrant profile, uniformly curved surface) that create localized flow patterns to prevent fuel deflection toward cylinder walls, thereby reducing particulate matter while maintaining overall engine efficiency
Solution Approach 2:
The invention specifies precise geometric parameters for the combustion bowl (diameter-to-depth ratio of 7:1, chamfer angle of 9° to 11°, non-reentrant profile) that optimize fuel-air mixing and combustion characteristics to reduce particulate emissions without sacrificing engine performance
2Object-generated harmful factors
If combustion bowl geometry is modified to reduce emissions, then particulate matter decreases, but engine efficiency is compromised
Solution Approach 1:
The combustion bowl is designed with specific parameters (7:1 diameter-to-depth ratio, non-reentrant profile, uniformly curved surface) that optimize combustion efficiency while reducing particulate matter, demonstrating that precise parameter control can achieve both emission reduction and efficiency maintenance
3Productivity
If fuel injection timing is advanced before top dead center, then combustion efficiency improves, but particulate matter emissions increase
Solution Approach 1:
The combustion bowl's localized geometric features (non-reentrant profile, uniformly curved surface) work synergistically with post-TDC injection timing to create optimal fuel-air mixing zones that maintain combustion efficiency while reducing particulate matter formation
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 design effectively reduces particulate matter production by directing fuel into the combustion bowl, preventing wall wetting and soot accumulation, while maintaining engine efficiency and meeting stringent emissions standards like Tier IV Final.
Implementation Method 1
The inner rim surface includes a chamfer sloping vertically downward from the plane at a chamfer angle from about 9° to about 11°, such that a profile of the annular rim is uniformly linear radially inward of the outer rim surface, and relieved to limit deflection by the piston of the directly injected fuel toward a wall of the cylinder bore
Implementation Method 2
combustion of the fuel and air produces exhaust from the internal combustion engine
Implementation Method 3
directly injected fuel toward a wall of a cylinder bore
Implementation Method 4
a fluid pressure within the cylinder bore is increased by a factor of about fifteen or greater to autoignite the directly injected fuel with air
Data Source
AI summary
A piston for reduced production of particulate matter during combustion of a fuel directly injected after a top dead center position includes a piston body defining a piston body diameter of about 263 mm, and a combustion face upon the first axial body end. The combustion face includes a combustion bowl, and an annular piston rim extending circumferentially around the combustion bowl. Inner and outer rim surfaces together comprise a horizontal width of the rim in a ratio of about 1:1 to about 2:1. The inner rim surface includes a chamfer sloping from about 9° to about 11°, such that a profile of the rim is relieved to limit deflection by the piston of the directly injected fuel toward a cylinder wall.