Two-Stroke Engine Scavenging Passage Configuration
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Solution Overview
Problem
Conventional two-stroke engines suffer from low scavenging and combustion efficiencies, leading to increased hydrocarbon and carbon monoxide emissions due to unburned mixture gas being exhausted with post-combustion gases.
Innovation Solution
The engine design includes a scavenging passage configuration with a communication passage that directs mixture gas towards the far side of the exhaust port, utilizing a landing portion to expand the space around the opening of the scavenging passage, promoting atomization and mixture of gases, and forming the scavenging ports in a divergent manner to enhance gas dispersion and pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the scavenging port and exhaust port are both opened to the cylinder in conventional two-stroke engines, then the scavenging process can be performed, but unburned mixture gas is exhausted together with post-combustion gas, increasing hydrocarbon emissions
Solution Approach 1:
The invention divides the scavenging process into two distinct phases: a first scavenging process where only the scavenging port is opened to introduce mixture gas, and a second scavenging process where both scavenging and exhaust ports are opened to expel unburned gas. This temporal segmentation allows separate optimization of mixture introduction and exhaust removal, reducing hydrocarbon emissions while maintaining scavenging efficiency
Solution Approach 2:
The invention performs preliminary action by opening the scavenging port first to introduce mixture gas into the combustion chamber before opening the exhaust port. This sequence ensures that fresh mixture is in position to push out residual gases, improving scavenging efficiency while controlling emission levels through staged port operation
2Object-generated harmful factors
If scavenging efficiency and combustion efficiency are low in conventional two-stroke engines, then the engine structure is simpler, but the amount of carbon monoxide contained in the exhaust gas increases
Solution Approach 1:
The invention introduces a communication passage that extends in the axial direction of the cylinder, creating a three-dimensional scavenging path. This axial dimension allows mixture gas to travel deeper into the combustion chamber and reach areas that conventional radial scavenging passages cannot effectively access, improving combustion efficiency and reducing carbon monoxide emissions
Solution Approach 2:
The communication passage acts as an intermediary structure that connects the scavenging port to the combustion chamber through a controlled path. This intermediary passage regulates the flow of mixture gas, directing it toward the far side from the exhaust port to optimize gas displacement and improve combustion efficiency while managing the complexity through a single integrated structure
3Power
If the cross-sectional area of the scavenging passage is made small to improve compression ratio, then the output performance can be enhanced, but the scavenging efficiency may be reduced
Solution Approach 1:
The invention employs dynamic port timing where the scavenging port and exhaust port are opened at different times during the piston cycle. The scavenging port opens first to introduce mixture, then the exhaust port opens to expel gases. This dynamic sequencing allows the use of a smaller scavenging passage cross-sectional area while maintaining scavenging efficiency, thereby enabling higher compression ratios and improved output performance
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 significantly reduces unburned gas exhaustion, improves scavenging and combustion efficiencies, and allows for a larger compression ratio, enhancing engine output performance while reducing hydrocarbon and carbon monoxide emissions.
Implementation Method 1
the mixture gas compressed in the scavenging passage is expanded in the communication passage
Implementation Method 2
promotes atomization and mixture of the mixture gas
Implementation Method 3
the mixture gas compressed in the scavenging passage is expanded in the communication passage and jetted in the combustion chamber
Data Source
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AI summary
An engine includes a cylinder block (60), and a piston (50) slidably mounted in a cylinder (61a), with the cylinder block being formed with an exhaust passage (80) leading to a combustion chamber (40) through an exhaust port (81), a first scavenging port (20A) opened to an inner circumferential surface of the cylinder (61A), a first communication passage (30A) formed from the first scavenging port (20A) in a radial direction of the cylinder (61A), and a first scavenging passage (10A) formed with an opening on a bottom surface of the first communication passage (30A), in which a side surface on a far side from the exhaust port (81) forming the communication passage (30A) is formed towards the far side from the exhaust port (81) in the combustion chamber (40), and the opening portion of the first scavenging passage (10A) and a landing portion (36) formed in the periphery of the opening portion are formed at a bottom portion of the communication passage (30A).