Low Compression Natural Gas Piston Bowl Combustion Stability
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Solution Overview
Problem
Natural gas engines face a tradeoff between achieving high power output and maintaining combustion stability and efficiency, often resulting in increased emissions of unburned hydrocarbons and nitrogen oxides.
Innovation Solution
A piston design featuring a contoured combustion bowl with a reentrant surface and a swirl pocket, optimized for a low geometric compression ratio, high squish velocity, and effective cooling, to enhance combustion efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high compression ratio is used to improve power output, then combustion efficiency deteriorates and emissions increase
Solution Approach 1:
The piston crown incorporates a reentrant surface with a specific reentrant angle (53.0° to 57.0°) that creates a curved, spherical-like combustion chamber geometry. This curvature optimizes the combustion chamber volume and improves combustion stability while maintaining low compression ratio, thereby resolving the contradiction between power output and combustion stability.
Solution Approach 2:
The invention changes the geometric parameters of the combustion chamber by introducing a reentrant surface with a controlled reentrant angle and optimizing the combustion chamber volume ratio. These parameter changes enable stable combustion at low compression ratios, breaking the traditional tradeoff between power output and combustion efficiency.
2Reliability
If a low compression ratio is used to improve combustion stability, then power output decreases
Solution Approach 1:
The reentrant surface creates an optimized combustion chamber geometry that maximizes combustion stability. The specific reentrant angle (53.0° to 57.0°) and combustion chamber volume ratio (0.45 to 0.55) enable stable combustion at low compression ratios, preventing power loss.
Solution Approach 2:
The invention applies local quality by creating a reentrant surface with specific geometric properties in the crown portion of the piston. This localized geometric feature optimizes the combustion chamber characteristics, enabling stable combustion without compromising overall engine power output.
3Reliability
If combustion efficiency is improved by optimizing piston geometry, then emissions of unburned hydrocarbons and nitrogen oxides increase
Solution Approach 1:
By optimizing the combustion chamber volume ratio (0.45 to 0.55) and reentrant angle (53.0° to 57.0°), the invention achieves complete and stable combustion. This reduces unburned hydrocarbon emissions while the low compression ratio design inherently limits nitrogen oxide formation, thus improving combustion efficiency without excessive emissions.
Solution Approach 2:
The reentrant surface geometry optimizes fuel-air mixing and combustion completeness. The curved surface area enhances flame propagation and ensures more complete combustion, reducing unburned hydrocarbon emissions while maintaining stable combustion characteristics.
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 piston design achieves improved combustion stability and efficiency, reducing unburned hydrocarbons and nitrogen oxides emissions while maintaining high power output, thus breaking the traditional tradeoff in natural gas engines.
Implementation Method 1
high squish velocity
Implementation Method 2
swirl pocket
Implementation Method 3
effective cooling
Implementation Method 4
cooling gallery
Data Source
AI summary
A piston may have an annular body including a crown portion defining a longitudinal axis, a radial direction perpendicular to the longitudinal axis, a plane containing the longitudinal axis and the radial direction, and a contoured combustion bowl. In the plane containing the longitudinal axis and the radial direction, the crown portion includes a radially outer squish surface, and a swirl pocket having a reentrant surface that extends axially downwardly and radially outwardly from the squish surface defining a tangent that forms a reentrant angle with the squish surface that ranges from 53.0 degrees to 57.0 degrees.