Piston Reentrant Bowl Geometry for Stable Low-Compression Combustion
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Solution Overview
Problem
Existing piston designs for internal combustion engines face challenges in achieving a balance between optimizing combustion stability, efficiency, and maintaining a low compression ratio, often requiring significant modifications to engine and supporting systems.
Innovation Solution
A piston design featuring a contoured combustion bowl with a reentrant surface and specific geometric ratios, including a reentrant angle of 28-32 degrees and a bowl volume to entry opening area ratio of 45-52 mm, which enhances combustion stability and efficiency while maintaining a low geometric compression ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a low compression ratio is used in natural gas engines, then fuel efficiency and emissions are improved, but combustion stability deteriorates
Solution Approach 1:
The combustion bowl incorporates a reentrant surface with a specific reentrant angle (28-32 degrees) that creates a curved, non-linear geometry. This curvature modifies the combustion chamber shape to enhance squish velocity and improve combustion stability while maintaining a low compression ratio, directly resolving the contradiction between fuel efficiency and combustion stability.
Solution Approach 2:
The invention changes the geometric parameters of the combustion bowl by specifying a reentrant angle between 28-32 degrees and a bowl volume to entry opening area ratio between 45-52 mm. These parameter changes optimize the combustion process to maintain stability at low compression ratios, enabling improved fuel efficiency without sacrificing combustion reliability.
2Reliability
If combustion bowl volume is increased to improve combustion stability, then geometric compression ratio increases, but engine system modifications are required
Solution Approach 1:
Instead of uniformly increasing the entire combustion chamber volume, the invention applies a localized reentrant surface feature with specific geometric characteristics (28-32 degree reentrant angle) to the combustion bowl. This local modification enhances combustion stability through improved squish velocity without significantly increasing the overall geometric compression ratio or requiring extensive engine system modifications.
Solution Approach 2:
The reentrant surface creates a curved geometry that optimizes the combustion bowl shape. This curvature enhances the squish effect and combustion stability while maintaining a compact design that fits within existing engine constraints, avoiding the need for major engine system modifications.
3Reliability
If squish velocity is increased to improve combustion stability, then piston temperatures increase, but cooling capacity may be compromised
Solution Approach 1:
The invention optimizes the reentrant angle (28-32 degrees) and bowl volume to entry opening area ratio (45-52 mm) to achieve an balance between squish velocity and temperature management. These parameter changes enhance combustion stability through improved squish while maintaining piston temperatures within acceptable ranges by optimizing the combustion bowl 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
The design improves combustion stability and efficiency by increasing squish velocity and reducing piston temperatures, thereby enhancing fuel efficiency and reducing unburned hydrocarbons without sacrificing bowl volume or cooling capacity.
Implementation Method 1
The design improves combustion stability and efficiency by increasing squish velocity
Implementation Method 2
reducing piston temperatures, thereby enhancing fuel efficiency
Data Source
AI summary
A piston for engine may include an annular body including a combustion bowl defining a volume and surrounded on a top side thereof by an annular crown portion defining a top squish surface with include an inner edge defining an opening to the combustion bowl. The opening may include an area for combustion gases to enter the bowl during a compression stroke of the piston. The combustion bowl may include a reentrant surface that defines a tangent that forms a reentrant angle with the top squish surface. The reentrant angle may range from 28.0 degrees to 32.0 degrees. A ratio of a bowl volume to an area of the entry opening may ranges from 45 mm to 52 mm. A ratio of a bowl volume to the reentrant angle may range from 12 cc/deg to 15 cc/deg.