Liquid-Phase Fuel Injection in Two-Stroke Engines to Limit Self-Ignition
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Solution Overview
Problem
Large two-stroke engines face challenges in reducing greenhouse gas emissions and improving efficiency due to unburned fuel escape and self-ignition issues, particularly when operating on gaseous fuels like natural gas.
Innovation Solution
Retrofitting the engines to inject liquefied gaseous fuel in liquid phase through nozzles in the cylinder wall, optimizing injection parameters such as pressure, temperature, and timing to minimize unburned fuel escape and self-ignition, allowing for increased compression ratios and improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel is injected in gas phase, then the risk of self-ignition is reduced, but the mass flow of injection is limited and unburned fuel escapes via exhaust valves
Solution Approach 1:
The patent changes the physical state parameter of the fuel from gas phase to liquid phase during injection. This parameter change enables significantly higher mass flow rates while the subsequent evaporation and mixing processes maintain controlled combustion characteristics, resolving the contradiction between injection quantity and self-ignition risk
Solution Approach 2:
The patent utilizes phase transition of fuel from liquid to gas during the injection and combustion process. The fuel is injected as liquid to achieve high mass flow, then evaporates and mixes with air in the combustion chamber, transitioning to gas phase for controlled combustion. This phase transition resolves the contradiction by separating the injection stage (liquid phase for high mass flow) from the combustion stage (gas phase for controlled burning)
2Productivity
If compression ratio is increased to improve efficiency, then engine efficiency improves, but self-ignition of fuel occurs
Solution Approach 1:
The patent changes the fuel injection parameters by injecting fuel in liquid phase at specific timing, which allows the fuel to evaporate and mix thoroughly before combustion. This parameter change enables operating at higher compression ratios (up to 18:1 or higher) without premature self-ignition, as the fuel-air mixture is properly prepared and the combustion is controlled by the injection timing rather than spontaneous ignition
Solution Approach 2:
The patent performs preliminary action by injecting the fuel in liquid phase before the compression stroke completes, allowing the fuel to evaporate and mix with air during the compression process. This preliminary evaporation and mixing action prepares the fuel-air mixture so that when compression reaches the ignition point, the fuel burns controllably without spontaneous self-ignition, enabling higher compression ratios for improved efficiency
3Quantity of substance
If fuel is injected closer to the wall, then fuel concentration near wall increases, but quenching of flame occurs and unburned fuel escapes
Solution Approach 1:
The patent changes the physical state parameter of fuel injection from gas phase to liquid phase. Liquid fuel injection creates a more concentrated jet that can be precisely controlled to reach specific locations near the wall. The liquid fuel evaporates upon contact with the hot combustion chamber surfaces, ensuring complete combustion even in wall-proximity regions, thus preventing quenching and unburned fuel escape while maintaining high fuel concentration where needed
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
Reduces greenhouse gas emissions and enhances engine efficiency by minimizing unburned fuel loss and self-ignition risks, while enabling higher compression ratios through optimized liquid phase fuel injection.
Implementation Method 1
a further benefit of the injection in liquid phase is that evaporation of the fuel reduces the temperature in the combustion chamber. The risk of self-ignition of the fuel is thus reduced
Data Source
Figure 1~3
Figure 4A~4C
AI summary
The method of operating a two-stroke piston engine (1) comprises the steps of supplying liquefied gaseous fuel to each cylinder (2) of the engine (1) and injecting the fuel into each cylinder (2) in liquid phase via at least one fuel injection nozzle (23) arranged in the wall of the cylinder (2).