Spark Ignition Engine Piston Cavity Flame Propagation
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Solution Overview
Problem
Spark ignited internal combustion engines with high geometric compression ratios face challenges in optimizing flame propagation and fuel efficiency, as higher compression ratios lead to earlier flame interference with combustion chamber surfaces, reducing engine efficiency and increasing fuel consumption.
Innovation Solution
A spark ignited internal combustion engine design featuring a combustion chamber with a spherical cavity on the piston head, where the ratio of the volume of the hypothetical sphere to the total combustion chamber volume at top dead center is optimized between 0.31 and 0.37, delaying flame interference while maintaining a geometric compression ratio of 13.0 or greater, thereby reducing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a larger spherical cavity is formed on the piston head to delay flame contact and shorten combustion period, then combustion period is shortened and operating efficiency is improved, but geometric compression ratio decreases leading to lower operating efficiency
Solution Approach 1:
The patent applies parameter changes by precisely controlling the volume ratio V2/V1 (where V2 is the non-interfering portion of the hypothetical sphere and V1 is the combustion chamber volume at TDC) to be 0.31 or greater. This quantitative parameter optimization allows the spherical cavity to delay flame contact effectively while maintaining sufficient compression ratio for high efficiency operation.
Solution Approach 2:
The patent utilizes spheroidality by forming a spherical cavity on the piston head that corresponds to a hypothetical sphere with its center at the spark plug gap. This spherical geometry naturally delays flame contact with the piston surface as the flame propagates radially outward, extending the combustion period without requiring complex cavity shapes.
2Use of energy by moving object
If geometric compression ratio is increased to improve heat efficiency and operating efficiency, then heat efficiency is improved, but flame contacts combustion chamber surface earlier causing longer combustion period
Solution Approach 1:
The patent resolves this contradiction by changing the parameter of combustion chamber geometry through the spherical cavity design. By optimizing the V2/V1 ratio to 0.31 or greater, the design enables high compression ratios (improving heat efficiency) while the spherical cavity compensates for early flame contact, preventing combustion period extension.
Solution Approach 2:
The spherical cavity acts as an intermediary element between the flame and the piston head surface. It provides a geometric buffer that delays flame contact with the piston, allowing the combustion chamber to maintain a small volume at TDC (high compression ratio) without suffering from premature flame-wall interaction.
3Loss of time
If spherical cavity volume is increased to delay flame interference, then flame interference is delayed and combustion period is shortened, but total combustion chamber volume increases reducing compression ratio
Solution Approach 1:
The patent applies parameter changes by establishing a critical threshold value for the volume ratio V2/V1 (0.31 or greater). This quantitative parameter defines the optimal balance point where the spherical cavity provides sufficient flame delay benefit without excessively increasing the combustion chamber volume, thus maintaining high compression ratio.
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 effectively shortens combustion duration and decreases fuel consumption rates, achieving improved engine efficiency and fuel economy while allowing for the production of engines with varying sizes at reduced development costs.
Implementation Method 1
a spark plug ignites air-fuel mixture in a combustion chamber around top dead center of the compression stroke
Implementation Method 2
flame of the ignited air-fuel mixture propagates from a spark point of the spark plug through the un-combusted mixture
Implementation Method 3
The spherical cavity can delay a timing of the first contact between the flame and the piston head surface because the spherical cavity has its center coincide with the spark plug gap at the top dead center
Data Source
AI summary
There is provided a spark ignited internal combustion engine having a geometric compression ratio of 13.0 or greater. The engine comprises combustion chambers having a cylinder stroke volume of 0.3 liter or greater, with the spark plug in the chamber ceiling having its spark point in the combustion chamber, and a cavity being formed on the top surface of the piston. At least part of the cavity defines a spherical surface that a hypothetical sphere having its center at the spark point contacts when the piston is at top dead center. The cavity is formed so that V2/V1≧0.31, where V1 is top-dead-center combustion chamber volume, and V2 is the volume of the part of the hypothetical sphere not interfering with the combustion chamber floor or ceiling at top dead center. The flame thus spreads with less interference, shortening combustion duration and reducing fuel consumption.