Segmented Piston Crown Design for Combustion Flame Control
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Solution Overview
Problem
Large four-stroke internal combustion engines face challenges in increasing power and reducing fuel consumption while minimizing emissions and mechanical stresses on pistons, requiring improved piston design to withstand higher loads and emissions, while also considering manufacturing costs and fatigue resistance.
Innovation Solution
A piston design featuring a piston crown with a raised center area and a depressed bowl area, optimized top land height, and strategically positioned piston rings to direct the combustion flame away from the cylinder wall, reducing HC-emissions and enhancing mechanical and thermal stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the mean effective pressure in the cylinders is increased to raise power rate, then the power output is improved, but the mechanical stresses on the piston and other components increase
Solution Approach 1:
The piston is divided into two separate parts: a piston crown and a piston skirt, which are fastened together but can be manufactured from different materials optimized for their specific functional requirements
Solution Approach 2:
Different materials are selected for different parts of the piston based on local requirements: the piston crown uses materials resistant to thermal and pressure loads, while the piston skirt uses materials optimized for power transfer and durability
2Weight of moving object
If the weight of moving parts is reduced to decrease internal mass forces, then the efficiency is improved, but the fatigue resistance and reliability may be compromised
Solution Approach 1:
The piston is constructed as a composite structure with the crown made from materials optimized for thermal and pressure resistance, and the skirt made from materials optimized for strength-to-weight ratio and fatigue resistance, achieving lightweight design without compromising reliability
3Adaptability or versatility
If the piston crown height is increased to adjust compression ratio, then the compression ratio is improved, but the piston weight and manufacturing complexity increase
Solution Approach 1:
The piston is segmented into crown and skirt parts that can be manufactured separately and assembled, allowing flexible adjustment of compression ratio by varying crown height without increasing overall piston complexity
Solution Approach 2:
The separate crown and skirt design allows the same basic piston structure to accommodate different compression ratios by simply changing the crown dimensions, making the design universally applicable to different engine requirements
Data Source
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AI summary
The present invention relates to a four-stroke internal combustion engine having at least one cylinder head (112), at least one cylinder (114) and a piston (116) in each cylinder (114); the at least one cylinder head (112) having at least one intake valve (120) and at least one exhaust valve (124); the piston (116) having a piston crown (140) and a piston skirt (142) fastened to one another by means of screws (144); the piston crown (140) having a top surface (146) facing the cylinder head (112); the top surface (146) being rotationally symmetric and having a centre area (146'), a depressed bowl area (146'') and an edge area (146'''), wherein the centre area is a raised centre area (146') extending above the edge area (146''').