Two-Stroke Engine Fuel Injection Piston Cooling
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Solution Overview
Problem
Two-stroke engines face challenges in cooling the piston and cylinder due to limited lubricating oil quantity, leading to increased complexity and manufacturing costs in existing cooling solutions.
Innovation Solution
A two-stroke engine design featuring a fuel injection device that injects fuel onto the backside of the piston and cylinder bore, enhancing cooling through evaporation and lubrication, while minimizing obstruction from the crankshaft and linkage members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If compressed air is blown against the back side of the piston via special passages, then the piston cooling is improved, but the device complexity and size increase due to requiring a pump and special passages
Solution Approach 1:
The fuel injection system serves dual purposes: delivering fuel to the combustion chamber and cooling the piston and cylinder. By injecting fuel onto the back side of the piston and cylinder bore, the system provides both combustion function and cooling function without requiring separate cooling infrastructure.
Solution Approach 2:
The fuel itself is used as the cooling medium. The fuel injected for combustion purposes simultaneously cools the piston and cylinder through evaporation and heat absorption, making the system self-sufficient without external cooling resources.
2Temperature
If a guide plate is provided to guide gas to the back side of the piston, then the piston cooling is improved, but the manufacturing cost increases and compatibility is impaired
Solution Approach 1:
The fuel injection system performs both fuel delivery and cooling functions. The injected fuel cools the piston and cylinder through evaporation and direct contact, eliminating the need for separate guide plates or cooling structures in the piston design.
3Reliability
If lubricating oil is supplied through the fuel system, then the rotating parts are lubricated, but the cooling capability is limited due to the small quantity of lubricating oil
Solution Approach 1:
The system changes the state of fuel from liquid to vapor through evaporation on hot surfaces. This phase change absorbs significant heat energy, providing effective cooling of the piston and cylinder while the liquid fuel also provides lubrication before evaporation.
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 fuel injection system effectively cools the piston and cylinder, improves lubrication, and maintains efficiency by delivering fuel directly to targeted areas without increasing engine size or complexity.
Implementation Method 1
the fuel is allowed to evaporate and otherwise favorably atomized owing to the contact with high temperature surfaces such as the piston and the cylinder wall
Implementation Method 2
Owing to the deposition of fuel on the back side of the piston and/or the inner circumferential surface of the cylinder bore, the cylinder and the piston are favorably cooled
Data Source
AI summary
In a two-stroke engine including a scavenging port (43b) having an open end (42d) opening out in a side wall of the cylinder bore (3a) and communicating with a crank chamber (2a), the open end being configured to be closed and opened by the piston (22), a fuel injection device (71) is mounted on the engine main body so as to inject fuel onto a back side of the piston and/or a part of the side wall of the cylinder bore located under the piston via the open end of the scavenging port or via the open lower end of the cylinder bore. The fuel deposited on the surfaces of the piston and the cylinder inner wall promotes the cooling of such parts.