Piston Crown Spray Impingement Geometry for Soot Reduction
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Solution Overview
Problem
Current piston crowns in internal combustion engines do not effectively control combustion processes to minimize soot, NOx, carbon monoxide, and hydrocarbon emissions, particularly due to inefficient fuel mixing and flame propagation.
Innovation Solution
A piston crown design featuring a circumferential rim portion with circumferentially spaced protrusions and a spray impingement portion with a reflection surface angled between 50° and 85° relative to the central axis, optimizing spray reflection and kinetic energy distribution within the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fuel is injected directly into the cylinder for diesel combustion, then engine power and efficiency are improved, but soot particle and NOx emissions increase
Solution Approach 1:
The piston crown is segmented into multiple functional zones: a central spray impingement portion for direct fuel injection, circumferential protrusions for flame propagation control, and a rim portion for turbulence generation. This segmentation allows different regions to perform specialized functions that collectively reduce soot emissions while maintaining engine power.
Solution Approach 2:
Different regions of the piston crown are designed with locally optimized geometries: the spray impingement portion has a specific angle (α) between 30° and 60° to control fuel spray direction, protrusions have specific heights (h) and spacing to enhance mixing, and the rim portion features grooves or ridges to generate turbulence. These local quality variations address emission problems in specific zones without compromising overall engine performance.
2Productivity
If combustion is performed with a fuel-rich mixture at high temperature, then engine efficiency is improved, but soot formation increases
Solution Approach 1:
The piston crown geometry, particularly the protrusions and rim portion features, is designed to generate controlled turbulence and chaotic flow patterns during combustion. This mechanical disturbance enhances fuel-air mixing and prevents localized fuel-rich zones that would otherwise lead to soot formation, while maintaining the high temperature and pressure conditions necessary for efficient combustion.
Solution Approach 2:
The piston crown acts as an intermediary structure between the fuel injection system and the combustion chamber. It mediates the combustion process by controlling spray impingement, generating turbulence, and directing flame propagation, thereby enabling efficient combustion while preventing excessive soot formation through its geometric features.
3Productivity
If the piston bowl surface is designed to affect flame propagation and mixing, then combustion efficiency is improved, but device complexity increases
Solution Approach 1:
The piston crown is divided into distinct functional segments: a central spray impingement portion with a defined angle α, circumferential protrusions at specific positions, and a rim portion with turbulence-generating features. This segmentation allows each zone to perform a specific combustion function while maintaining a relatively simple overall structure that can be manufactured using conventional piston manufacturing processes.
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 enhances fuel consumption efficiency, reduces soot emissions, and improves combustion conditions by directing the spray and flame effectively, leading to better engine performance.
Implementation Method 1
a spray impingement portion, located between two adjacent protrusions... The spray impingement portion comprises a reflection surface, being defined by that each possible normal to the reflection surface is directed towards a central axis (A) of the piston
Implementation Method 2
When the fuel is ignited in the cylinder, combustion gases present in the cylinder undergo turbulent mixing with the burning fuel, so that a mixture-controlled diffusion flame is formed. The combustion of the fuel/gas mixture in the cylinder gives rise to heat generation which causes the gas in the cylinder to expand
Implementation Method 3
combustion gases present in the cylinder undergo turbulent mixing with the burning fuel
Data Source
AI summary
A piston crown is provided for a piston in an internal combustion engine arrangement that includes a cylinder, the piston crown having a piston bowl surface adapted for facing a combustion chamber in the cylinder, wherein the piston bowl surface including a circumferential rim portion, a floor portion connected to and surrounded by the circumferential rim portion, a plurality of circumferentially spaced protrusions in the circumferential rim portion, at least one spray impingement portion, located between two adjacent protrusions. The spray impingement portion includes a reflection surface, being defined by that each possible normal to the reflection surface is directed towards a central axis of the piston, and forming an angle being within a range of a constant angle ±10° with the central axis, wherein the constant angle is at least 50°.