Piston Crown Cavity Geometry for Stable Tumble Flow Combustion
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Solution Overview
Problem
In spark-ignition internal combustion engines with a protrusion on the piston and a cavity associated with the spark plug, the tumble flow is often decelerated, reducing turbulence energy and fuel efficiency.
Innovation Solution
The engine design includes a protrusion on the piston with a cavity positioned to retard the initial flame front interference, featuring inclined surfaces with specific angle differences to minimize tumble flow deceleration, while maintaining a high geometric compression ratio and efficient fuel injection patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a protrusion is formed on the piston top surface with a cavity in the middle, then flame propagation is increased and fuel efficiency is improved, but the tumble flow is decelerated and turbulence energy is reduced
Solution Approach 1:
The patent applies local quality by creating a cavity only in the central region of the protrusion where the spark plug is located, rather than modifying the entire piston surface. This localized cavity structure allows the tumble flow to maintain its velocity along the piston's outer peripheral surface while still achieving the desired flame propagation enhancement in the combustion chamber center region.
Solution Approach 2:
The protrusion is segmented into different functional zones: an outer peripheral region that maintains smooth surfaces for tumble flow passage, and a central region containing the cavity for flame propagation enhancement. This segmentation allows different parts of the protrusion to serve different purposes without interfering with each other.
2Productivity
If a protrusion is formed on the piston to increase geometric compression ratio, then combustion efficiency is improved, but the tumble flow path is obstructed and turbulence is reduced
Solution Approach 1:
The cavity is extracted from the center of the protrusion, creating a void space that allows the tumble flow to pass through or around the protrusion structure without significant obstruction. This extraction of material from the protrusion center reduces the flow path blockage while maintaining the compression ratio enhancement benefits.
Solution Approach 2:
The cavity introduces a vertical dimension to the protrusion structure, allowing the tumble flow to move through the three-dimensional space created by the cavity rather than being constrained to a two-dimensional surface path. This dimensional change provides additional flow paths that reduce obstruction effects.
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 configuration enhances flame propagation, maintains high turbulence energy, and increases fuel efficiency by ensuring the tumble flow is not excessively decelerated, thus promoting stable combustion.
Implementation Method 1
a so-called tumble port capable of generating a tumble flow (vertical vortex) within a combustion chamber may be employed as an intake port
Implementation Method 2
combustion is promoted by turbulence, which is generated by collapse of a tumble flow
Implementation Method 3
a spark plug 105 and a fuel injection valve 106 mounted in the cylinder head
Implementation Method 4
flame propagation is increased
Data Source
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AI summary
In a spark-ignition internal combustion engine in which a protrusion (31) including an intake-side inclined surface (34) and an exhaust-side inclined surface (35) is formed on a top surface (10) of a piston (5), and a cavity (40) is formed in the protrusion (31) at a position associated with a spark plug, the intake-side inclined surface (34) and the exhaust-side inclined surface (35) are formed in such a way that an angle defined by an orthogonal plane orthogonal to a center axis of a cylinder and the exhaust-side inclined surface (35) is smaller than an angle defined by the orthogonal plane and a valve head bottom surface of an exhaust valve, and an inclination angle difference between the exhaust-side inclined surface (35) and the valve head bottom surface of the exhaust valve is larger than an inclination angle difference between the intake-side inclined surface (34) and a valve head bottom surface of an intake valve by 3 degrees or larger.