Piston Bowl Geometry for Lean Combustion Flame Jet Propagation
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Solution Overview
Problem
Existing piston designs for internal combustion engines with pre-chambers lead to unfavorable clearance volume shapes, resulting in unsatisfactory combustion behavior, particularly with lean fuel-air mixtures.
Innovation Solution
A piston crown design featuring at least one piston bowl with a lower surface level than the radial edge region, optimized to position the majority of the clearance volume between the center and the cylinder wall, enhancing flame jet ignition efficiency and combustion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a piston with a roof top design is used, then the piston structure is simple and easy to manufacture, but the clearance volume shape is unfavorable leading to high combustion duration
Solution Approach 1:
The patent applies curvature by introducing a piston bowl with a rounded, bowl-shaped depression in the piston crown, replacing the flat roof top design. This curved geometry creates a favorable clearance volume shape that directs flame propagation more efficiently, reducing combustion duration while maintaining manufacturability through standard machining processes.
2Device complexity
If the clearance volume is positioned near the piston skirt at the cylinder wall, then the piston design is conventional, but the flame jets reach the main portion of the clearance volume late resulting in high combustion duration
Solution Approach 1:
The patent applies local quality by creating a non-uniform clearance volume distribution through the piston bowl geometry. The bowl shape concentrates the clearance volume in specific regions that are more accessible to flame jets from the pre-chamber, while maintaining conventional overall piston design. This localized optimization of clearance volume positioning accelerates flame propagation without requiring radical design changes.
3Power
If a lean fuel-air mixture is ignited in a large volume cylinder, then maximum power and high efficiency are achieved, but the ignition and combustion process becomes challenging requiring ignition amplifiers
Solution Approach 1:
The patent applies preliminary action by using a pre-chamber to pre-ignite a portion of the fuel-air mixture before the main combustion event. The piston bowl geometry works in conjunction with the pre-chamber to create favorable flow patterns that enhance flame jet propagation into the main combustion chamber, ensuring reliable ignition of lean mixtures in large volume cylinders while maintaining high power output.
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
The optimized piston crown shape improves combustion efficiency by allowing flame jets to reach the main portion of the clearance volume faster, reducing combustion duration, and increasing energy conversion rates, while maintaining a constant compression ratio.
Implementation Method 1
allowing flame jets to reach the main portion of the clearance volume faster
Data Source
AI summary
Piston for an internal combustion engine, preferably a gas engine comprising a pre-chamber, comprising a piston crown limiting the piston on a side facing a cylinder head when the piston is arranged inside an internal combustion engine, wherein the piston crown comprises at least one piston bowl which has a lower surface level than a radial edge region of the piston crown, wherein the piston bowl comprises a depth (d), which is defined by the distance between the radial edge region and the lower surface level of the piston bowl measured parallel to central elevation which has a height (H), wherein the height (H) of the central elevation equals the depth (d) of the piston bowl plus/minus 50%, preferably 20%, of the depth (d) of the piston bowl.