Uniflow Scavenging Two-Stroke Engine Fuel Injection Control
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Solution Overview
Problem
Conventional uniflow-scavenging-type two-cycle engines face challenges in evenly distributing fuel gas across the cylinder, leading to suboptimal operational performance, particularly in large-diameter engines like those for ships.
Innovation Solution
The engine incorporates a fuel injection control unit that adjusts the injection directions of fuel gas based on load state and blow-by detection, using fuel injection valves that can vary their injection angles and flow passage cross-sectional areas to ensure widespread fuel distribution within the cylinder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fuel gas is injected toward the center of the cylinder from multiple fuel injection valves, then the injection system is simple to control, but the fuel gas cannot be spread widely over the whole internal area of the cylinder
Solution Approach 1:
The fuel injection valves are equipped with adjustable injection directions that can be dynamically changed based on operating conditions. The injection directions are made variable rather than fixed, allowing the system to adapt to different load conditions and optimize fuel distribution across the cylinder internal area.
Solution Approach 2:
The injection parameters (injection direction angles) are changed based on load conditions. At high loads, injection directions are set along the swirl flow direction to maximize fuel distribution. At low loads, injection directions are adjusted to different angles to maintain proper fuel-air mixing while accounting for reduced gas flow velocities.
2Device complexity
If fuel injection direction is fixed, then the device structure is simple, but the engine cannot adapt to varying load conditions for optimal performance
Solution Approach 1:
The injection valve structure incorporates movable components that allow the injection direction to be adjusted. This dynamic capability enables the system to adapt to varying load conditions while maintaining a relatively compact and integrated valve design that does not require completely separate injection systems for different operating modes.
Solution Approach 2:
The fuel injection valve is designed to perform multiple functions: it can inject fuel in different directions to accommodate both high-load and low-load conditions, and it can control fuel distribution patterns to optimize combustion across varying operating conditions. This multi-functionality is achieved within a single integrated valve structure.
3Device complexity
If fuel gas is injected uniformly from all injection valves, then the control system is simple, but abnormal combustion may occur under certain load conditions
Solution Approach 1:
The injection system applies different injection directions to different injection valves based on their specific positions in the cylinder. Each valve's injection direction is optimized for its local location and the prevailing flow conditions, ensuring proper fuel distribution and preventing localized rich or lean zones that could cause abnormal combustion.
Solution Approach 2:
The control system receives feedback about engine operating conditions (load, speed, etc.) and adjusts the injection directions accordingly. This feedback mechanism allows the system to maintain optimal fuel distribution and prevent abnormal combustion by adapting injection patterns to actual operating conditions rather than using fixed uniform injection.
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 approach enhances operational performance by ensuring uniform fuel distribution, reducing the risk of abnormal combustion and improving power output across varying load conditions.
Implementation Method 1
a plurality of fuel injection valves that inject a fuel gas to the active gas, which has been drawn in from the scavenging port to the combustion chamber, to thereby generate a premixed gas
Implementation Method 2
the generated premixed gas is compressed
Implementation Method 3
in the compressed premixed gas, a pilot fuel is injected, to thereby obtain a combustion action of the premixed gas ignited by the combustion of the pilot fuel. With an explosive pressure generated by the combustion action, the piston reciprocates in the cylinder
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A uniflow-scavenging-type two-cycle engine (100) includes: a cylinder (110); a piston (112) that slides in the cylinder; an exhaust port (116) that is provided at a first end of the cylinder; an exhaust valve (120) that opens and closes the exhaust port; a scavenging port (122) that is provided in an inner circumferential surface of a second end of the cylinder in the stroke direction of the piston and inhales an active gas into a combustion chamber (140) in accordance with a sliding movement of the piston; a plurality of fuel injection valves (128) that inject a fuel gas to the active gas, which has been drawn in from the scavenging port to the combustion chamber, to thereby generate a premixed gas; and a fuel injection control unit (152) that varies injection directions of fuel gas injected from a part or all of the fuel injection valves (128).