Two-Stroke Engine Scavenging Port Fuel Injection
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Solution Overview
Problem
Two-stroke engines face challenges in reducing hydrocarbon emissions due to blow-by, particularly when using stratified scavenging with long piston strokes, which requires high-pressure injection systems and increased piston skirt length, and in-cylinder injection necessitates costly high-pressure systems.
Innovation Solution
A two-stroke engine design featuring multiple fuel injection valves controlled by a unit to inject fuel into the scavenging port, delaying the start of injection beyond the scavenging port opening and terminating before closure, allowing for stratified scavenging without a high-pressure system, using compact, low-cost valves and optimizing fuel delivery timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If in-cylinder injection is used to reduce THC emissions, then unburned fuel release is suppressed, but a high pressure injection system is required which increases cost
Solution Approach 1:
The patent uses the scavenging port as an intermediary location for fuel injection. Instead of injecting directly into the combustion chamber (which would require high pressure), fuel is injected into the scavenging port where it mixes with the incoming air-fuel mixture. This lower-pressure injection point serves as a mediator that achieves emission reduction without requiring complex high-pressure systems.
2Object-generated harmful factors
If stratified scavenging is applied to long-stroke engines to suppress blow-by, then air-fuel mixture release is reduced, but it requires either forming an air passage or increasing piston skirt length which causes contact problems or weight increase
Solution Approach 1:
The patent applies preliminary action by injecting fuel into the scavenging port before the air-fuel mixture enters the combustion chamber. This timing allows the fuel to mix with the scavenging air in advance, creating a stratified charge that reduces blow-by emissions. The fuel injection occurs during the scavenging phase, preparing the mixture before compression and combustion, thereby achieving emission control without modifying piston geometry.
3Device complexity
If multiple fuel injection valves are provided for low-cost fuel injection, then compact general-purpose valves can be used, but fuel must be injected into the scavenging port which requires precise timing control
Solution Approach 1:
The patent employs feedback control through the control unit that monitors engine operating conditions and adjusts the fuel injection timing accordingly. The control unit receives information about piston position, scavenging port status, and engine load to optimize the injection timing. This feedback mechanism ensures that fuel is injected at the optimal moment during the scavenging phase, maintaining stratified charge effectiveness across varying operating conditions while using simple injection valves.
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 enables effective stratified scavenging to suppress blow-by in long-stroke engines without a high-pressure injection system, using compact and cost-effective fuel injection valves, improving fuel delivery timing and reducing errors in fuel injection.
Implementation Method 1
a one-way valve (54) for opening and closing the intake passage
Implementation Method 2
a piston (23) reciprocably provided in the cylinder and defining a combustion chamber (29) in the cylinder
Implementation Method 3
multiple fuel injection valves (68) for injecting fuel into the scavenging port
Implementation Method 4
an exhaust valve (32) for opening and closing the exhaust port
Data Source
AI summary
A two-stroke engine includes: a scavenging port communicating with a crank chamber and a side portion of a cylinder, and switchably brought into communication with or shut off from the cylinder by a piston; and multiple fuel injection valves for injecting fuel into the scavenging port. Since the fuel injection valves inject fuel into the scavenging port, there is no need to apply a high pressure injection system. By causing the start of fuel injection to be delayed from a timing at which the scavenging port is opened, fresh air is sent into the cylinder at an early stage of scavenging, and air-fuel mixture is sent into the cylinder at a late stage of scavenging. Thereby, even in a long-stroke engine, stratified scavenging is performed to suppress blow-by of air-fuel mixture.