Uniflow Two-Stroke Engine Dual Fuel Injection for Uniform Mixing
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Solution Overview
Problem
In uniflow-scavenged two-cycle engines, insufficient mixing of fuel gas and active gas leads to non-uniform premixed gas distribution within the combustion chamber, resulting in inefficient combustion due to areas with lower flow velocity at the center of the cylinder.
Innovation Solution
The engine employs a fuel injection method with both first and second fuel injection portions, where the first injection occurs before active gas import and the second injection occurs after, ensuring uniform premixed gas distribution by injecting fuel gas into the combustion chamber from multiple ports arranged circumferentially, including oval-shaped scavenging ports with tapers to enhance gas flow uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If fuel gas is injected only after active gas is imported into the combustion chamber, then the mixing time of fuel gas and active gas inside the cylinder is extended, but the flow velocity becomes non-uniform with low velocity areas at the center, resulting in non-uniform premixed gas distribution
Solution Approach 1:
The fuel injection process is divided into two distinct segments: first injection into the scavenging port before active gas import, and second injection into the combustion chamber after active gas import. This segmentation allows each injection to serve a specific purpose - the first ensures uniform distribution throughout the cylinder, while the second ensures adequate mixing time in the combustion chamber.
Solution Approach 2:
Fuel gas is injected into the scavenging port before active gas is imported into the combustion chamber. This preliminary action ensures that fuel gas is already present and uniformly distributed in the scavenging port, so when active gas flows in, it immediately mixes with the fuel gas, preventing low-velocity stagnation areas.
2Quantity of substance
If the mixing between fuel gas and active gas is insufficient, then the density of fuel gas may be partially increased, but problems such as preignition and discharge of unburned gas occur
Solution Approach 1:
Fuel gas is injected into the scavenging port before active gas import, allowing preliminary mixing to occur. This ensures that when compression begins, the fuel gas and active gas are already well-mixed, preventing preignition caused by localized high-density fuel regions and avoiding unburned gas discharge.
Solution Approach 2:
The injection timing is changed to occur before active gas import rather than after, fundamentally altering when the mixing process begins. This parameter change ensures that mixing occurs during the scavenging phase when gas flow is most effective, rather than during compression when flow patterns are less favorable for mixing.
3Power
If fuel gas is injected into the combustion chamber after active gas import, then combustion can occur, but areas with thin premixed gas remain in the center of the cylinder, reducing combustion efficiency
Solution Approach 1:
The injection system is segmented into two locations: scavenging port injection and combustion chamber injection. The scavenging port injection ensures uniform distribution across the entire cylinder cross-section, while the combustion chamber injection ensures adequate mixing. This segmentation eliminates the problem of thin premixed gas areas in the cylinder center.
Solution Approach 2:
The injection approach transitions from a single-point injection into the combustion chamber to a two-stage injection system that operates in different spatial dimensions - first in the scavenging port (peripheral region) and then in the combustion chamber (central region). This dimensional approach ensures comprehensive coverage and uniform distribution.
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 ensures uniform premixed gas supply and efficient combustion by eliminating areas with thin combustion gas, enhancing engine output and preventing unburned gas discharge.
Implementation Method 1
fuel gas is injected into active gas imported to the scavenging port (122), thereby producing premixed gas
Implementation Method 2
The combustion operation is obtained by compressing the produced premixed gas
Implementation Method 3
the pilot injection valve (114) injects pilot fuel into the produced and compressed premixed gas, thereby igniting the premixed gas
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The uniflow-scavenged two-cycle engine (100) includes: a cylinder (110); a piston (112) which slides inside the cylinder; a scavenging port (122) which is provided on one end-side of the cylinder and which imports active gas into the cylinder in accordance with sliding movement of the piston; a first fuel injection portion (126) which is provided on the scavenging port and which injects fuel gas into the active gas imported to the scavenging port; and a second fuel injection portion (128) which is provided at a position closer to another end of the cylinder than the scavenging port and which injects fuel gas into the active gas imported from the scavenging port into the cylinder.