Uniflow Scavenging Port for Variable Compression Ratio Engines
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Solution Overview
Problem
In dual-fuel engines with variable compression ratios, the scavenging efficiency is compromised at high compression ratios when using a skewed scavenging port, as the swirling flow becomes weak, leading to reduced scavenging efficiency and increased blow-by of fuel gas.
Innovation Solution
A uniflow scavenging two-cycle engine with a scavenging port that includes both a swirling guide portion and a center guide portion, where the center guide portion's orientation adjusts relative to the piston position, ensuring effective scavenging gas flow and distribution regardless of compression ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a skewed scavenging port is used to level scavenging speed, then blow-by of fuel gas is reduced at low compression ratio, but swirling flow becomes weak at high compression ratio leading to reduced scavenging efficiency
Solution Approach 1:
The scavenging port is divided into two distinct portions: a first portion with an inclined surface that generates swirling flow, and a second portion with a surface parallel to the radial direction that levels scavenging speed. This segmentation allows each portion to independently fulfill its specific function, resolving the contradiction between generating swirl and leveling speed across different compression ratios
Solution Approach 2:
Different portions of the scavenging port are given different local qualities: the first portion has an inclined surface configuration optimized for generating swirling flow, while the second portion has a parallel surface configuration optimized for leveling scavenging speed. This local differentiation enables the port to address multiple conflicting requirements simultaneously
2Reliability
If the scavenging port is designed for high compression ratio, then scavenging efficiency is improved, but blow-by increases at low compression ratio
Solution Approach 1:
The scavenging port is segmented into two functional portions that operate complementarily: the first portion generates swirling flow to improve scavenging efficiency, while the second portion levels the scavenging speed to prevent blow-by. This segmentation allows the system to achieve both improved scavenging and reduced blow-by simultaneously
Solution Approach 2:
The invention merges two previously separate port designs into a single integrated scavenging port structure. The first portion (inclined surface) and second portion (parallel surface) are combined in one port, allowing the system to achieve both swirling flow generation and speed leveling effects in a unified component
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 engine achieves appropriate scavenging efficiency across varying compression ratios by optimizing gas flow patterns, reducing blow-by and maintaining effective scavenging performance in both low and high compression modes.
Implementation Method 1
a swirling guide portion that guides scavenging gas from an outside to an inside of the cylinder in a direction inclined with respect to a radial direction of the cylinder
Implementation Method 2
a center guide portion that is provided to be closer to the other end side of the cylinder than the swirling guide portion and guides the scavenging gas further toward the center side of the cylinder than the swirling guide portion
Implementation Method 3
a piston that reciprocates in the cylinder
Implementation Method 4
an exhaust port formed on one end side of a cylinder in which a piston reciprocates
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
A uniflow scavenging two-cycle engine includes an scavenging port (126) that has a swirling guide portion (126a) that guides scavenging gas from an outside to an inside of a cylinder (110) in a direction inclined with respect to a radial direction of the cylinder, and a center guide portion (126b) that is provided to be closer to a crank side of the cylinder than the swirling guide portion and guides the scavenging gas further toward the center side of the cylinder than the swirling guide portion. At least a part of the center guide portion faces a piston (112) in a case where the piston is positioned at bottom dead center during the high compression ratio mode, and the center guide portion and the piston do not face each other or an area of facing the piston is smaller than that during the high compression ratio mode in a case where the piston is positioned at bottom dead center during the low compression ratio mode.