Curved Piston Cavity Combustion Chamber for Engine Ignition
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Solution Overview
Problem
In engines performing compression self-ignition, fuel injection during the second half of the compression stroke to the first half of the expansion stroke results in poor ignitability and homogeneity of the fuel-air mixture due to the short time available for fuel-air mixture supply, leading to inefficiencies in combustion and increased emissions.
Innovation Solution
A combustion chamber structure with a concave piston cavity and strategically positioned fuel injection valve and spark plug, where the cavity's curved surface gradually increases in curvature, allowing the fuel-air mixture to maintain momentum and distribute evenly around the spark plug and squish area, ensuring proper ignition and mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fuel is injected in a period from a second half of a compression stroke until a first half of an expansion stroke to suppress preignition, then preignition is suppressed, but ignitability of the fuel-air mixture deteriorates due to short time for mixture supply
Solution Approach 1:
The piston cavity is designed with a curved surface having specific curvature characteristics. The curvature is smaller at the radially inner side and larger at the radially outer side, creating an optimized flow path that maintains fuel-air mixture momentum while directing it toward the spark plug, thereby resolving the contradiction between preignition suppression and ignitability
Solution Approach 2:
The curved surface of the piston cavity has non-uniform curvature distribution - smaller curvature at the radially inner side and larger curvature at the radially outer side. This local variation in geometric properties optimizes the fuel-air mixture flow characteristics in different regions, maintaining ignitability while suppressing preignition
2Object-affected harmful factors
If fuel is injected in a period from a second half of a compression stroke until a first half of an expansion stroke, then preignition is suppressed, but homogeneity of the fuel-air mixture deteriorates due to short time for mixing
Solution Approach 1:
The curved surface geometry with varying curvature promotes uniform distribution of the fuel-air mixture in the combustion chamber. The specific curvature profile ensures that the mixture maintains its momentum while being directed evenly toward the spark plug and squish area, achieving both preignition suppression and mixture homogeneity
Solution Approach 2:
The invention changes the geometric parameters of the piston cavity by defining a curved surface with specific curvature characteristics. This parameter optimization enables the fuel-air mixture to achieve homogeneous distribution within the shortened injection timing window, while still suppressing preignition
3Speed
If the curvature of the curved surface becomes larger as it extends toward the radially outer side, then momentum of the fuel-air mixture is maintained, but the mixture must be precisely directed to avoid poor combustion
Solution Approach 1:
The curved surface is designed with a specific curvature gradient - smaller at the radially inner side and larger at the radially outer side. This geometric configuration naturally guides the fuel-air mixture flow to maintain momentum while directing it toward the spark plug and squish area, achieving the desired flow control through optimized geometry
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 secures both the ignitability and homogeneity of the fuel-air mixture, improving fuel efficiency and reducing emissions by ensuring complete combustion and minimizing after-burning.
Implementation Method 1
the curvature of the curved surface becomes larger as the curved surface extends toward the radially outer side; a tangential direction of an edge end portion of the curved surface intersects with a combustion chamber ceiling
Data Source
AI summary
The present invention relates to a combustion chamber structure of an engine configured to inject fuel in a predetermined operation range in a period from a second half of a compression stroke until a first half of an expansion stroke to perform ignition after a compression top dead center. The combustion chamber structure includes: a piston including a cavity; a fuel injection valve provided at a middle portion of the piston; and a spark plug provided at a radially outer side of the middle portion of the piston and an upper side of the cavity. The cavity is formed by a curved surface having curvature that becomes larger as the curved surface extends toward the radially outer side. A tangential direction of an edge end portion of the curved surface intersects with a combustion chamber ceiling radially outward of the spark plug.