Two-Stroke Engine Piston With Communication Passage For Scavenging
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Solution Overview
Problem
Conventional two-stroke engines face issues with the blow-by phenomenon, leading to increased fuel consumption and atmospheric contamination, and stratified scavenging engines struggle with reduced combustion efficiency, carburetor adjustment sensitivity, and larger engine size due to air-fuel mixture density requirements and piston length.
Innovation Solution
A new two-stroke engine design featuring a communication passage on the piston that opens to both the air intake and scavenging ports, forming a diluted air-fuel mixture to reduce blow-by and emissions, while maintaining efficient combustion and allowing for stable carburetor adjustments across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If stratified scavenging is used to prevent blow-by phenomenon, then unburned fuel emissions are reduced, but combustion efficiency decreases due to local air remaining in the combustion chamber
Solution Approach 1:
The piston is divided into multiple functional zones with different port openings: a first port opening to the air intake port and a second port opening to the scavenging port. This segmentation allows different air-fuel mixtures to be introduced into different regions of the combustion chamber, preventing blow-by while maintaining combustion efficiency through controlled mixture distribution.
2Object-generated harmful factors
If air-fuel mixture density is increased for stratified scavenging, then blow-by is prevented, but carburetor adjustment becomes sensitive and difficult
Solution Approach 1:
Different regions of the combustion chamber receive different air-fuel mixture densities through the segmented piston ports. The first port introduces a first air-fuel mixture with a first density while the second port introduces a second air-fuel mixture with a second density. This local quality variation allows effective scavenging without requiring uniformly high mixture density throughout, thereby reducing carburetor sensitivity.
3Object-generated harmful factors
If communication passage is configured to communicate with neither cylinder chamber nor crank chamber over piston stroke, then stratified scavenging is achieved, but piston length increases and engine size becomes large
Solution Approach 1:
The piston ports are dynamically opened and closed during the piston stroke to control the timing of air-fuel mixture introduction. The first port opening to the air intake port and the second port opening to the scavenging port are strategically positioned to open at appropriate moments, achieving effective scavenging without requiring excessive piston length.
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 effectively restricts unburned fuel emissions, maximizes engine output across diverse conditions, and reduces engine size by using a diluted air-fuel mixture that does not interfere with ignition, allowing for stable operation and efficient carburetor adjustments.
Implementation Method 1
the diluted air-fuel mixture flows via the scavenging port into the scavenging passage
Implementation Method 2
a piston reciprocating in the bore of the cylinder
Implementation Method 3
a down-stroke of the piston allows the air-fuel mixture to be compressed
Implementation Method 4
the combustion gas can be exhausted
Data Source
AI summary
In a two-stroke engine (1) according to the present invention, a piston (6) has a communication passage (28) opened to a crank chamber (10). An air intake port (30) is provided on an inner surface (2a) for causing air to flow into the communication passage (28). After a scavenging port (22) is closed by an outer surface (6a) of the piston (6) moving from the bottom dead center to the top dead center, the communication passage (28) is opened in the outer surface (6a) of the piston so as to communicate with the air intake port (30) and the scavenging port (22).