Piston Crown Cavity Structure for Lean Combustion
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Solution Overview
Problem
Current engine combustion chamber structures fail to create a uniform, lean mixed gas effectively, leading to insufficient combustion and increased emissions such as NOx, CO, HC, and PM, due to inadequate distribution of fuel in the combustion chamber.
Innovation Solution
The engine combustion chamber structure features a two-stage cavity in the piston's crown face, with a first cavity in the central region and a second cavity on the outer circumference, connected by a tapered region, which allows for spatial and chronological separation of fuel injection, ensuring uniform mixing of fuel and air across the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single cavity structure is used in the piston crown face, then the device complexity is low, but the mixed gas uniformity and lean combustion quality deteriorate
Solution Approach 1:
The cavity in the piston crown face is divided into multiple separate cavities (e.g., central cavity and peripheral cavities) instead of a single large cavity. This segmentation allows fuel injected into each cavity to mix with air independently, creating multiple streams of lean mixed gas that combine to form a more uniform overall distribution throughout the combustion chamber, directly addressing the mixed gas uniformity issue.
Solution Approach 2:
Different regions of the combustion chamber are provided with cavities having different characteristics (central cavity vs. peripheral cavities with different sizes and positions). Each cavity is optimized for its specific location to promote localized mixing and flow patterns that collectively achieve uniform lean combustion across the entire chamber.
2Object-generated harmful factors
If fuel is injected toward the inner wall of the combustion chamber, then the fuel injection process is simple, but emission increases due to insufficient mixing and local rich regions
Solution Approach 1:
The fuel injection system is segmented into multiple injection points or stages, with fuel injected into different cavities at different timings. This prevents the formation of a single large rich region near the inner wall and promotes distributed mixing throughout the combustion chamber, reducing emissions.
Solution Approach 2:
Fuel is injected into the cavities before the main combustion event, allowing preliminary mixing with air to occur in the confined cavity spaces. This pre-mixing action ensures that when combustion occurs, the fuel is already well-distributed and mixed, preventing local rich regions and reducing emissions.
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 the creation of a uniform, lean mixed gas, reducing emissions like soot by effectively utilizing the combustion chamber space and preventing fuel from interfering with the inner wall, thus improving fuel efficiency and combustion quality.
Implementation Method 1
Fuel is supplied into the combustion chamber from a fuel injection valve
Implementation Method 2
fuel mixes with the air in the combustion chamber to form a mixed gas
Implementation Method 3
the mixed gas flowing along the upper cavity to sufficiently progress to a radially outer side of the combustion chamber
Implementation Method 4
a mixed gas is combusted in the combustion chamber
Data Source
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AI summary
An engine combustion chamber structure includes a combustion chamber of an engine and a fuel injection valve. The fuel injection valve injects fuel toward a cavity in a crown face of a piston. The cavity includes a first cavity that is provided in a radially central region of the crown face and includes a first bottom having a first depth in a cylinder axial direction, a second cavity that is provided in the crown face to be in an outer side of an outer circumference of the first cavity and includes a second bottom having a second depth in the cylinder axial direction, the second depth being smaller than the first depth, a connecting portion that connects the first cavity to the second cavity, and a standing wall region disposed further in a radially outer side than the second bottom of the second cavity. The second bottom is provided lower than an upper end, regarding a cylinder axial direction, of the connecting portion. A lower section of the standing wall region is provided further in a radially inner side than an upper edge of the standing wall region.