Combustion Engine Fuel Nozzle Double-Layer Passage Wall
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Solution Overview
Problem
Compression-ignition internal combustion engines face challenges in maintaining the shape and reducing the wall surface temperature of flow guide passages due to exposure to high-temperature combustion gases and repeated loads, which can lead to self-ignition issues and reduced thermal efficiency.
Innovation Solution
A double-layered structure for the passage wall portion is implemented, where the first layer is tougher and has higher thermal conductivity, connected to the cylinder head, and the second layer is less tough and has lower thermal conductivity, acting as a heat-shielding film to prevent heat transfer and maintain shape integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the duct is exposed in the combustion chamber to enable fuel injection, then fuel can be injected into the combustion chamber, but the duct temperature increases and shape retention reliability decreases due to high-temperature combustion gases and repeated loads
Solution Approach 1:
The passage wall portion is constructed with a composite structure consisting of a base material layer and a ceramic coating layer. The ceramic coating has lower thermal conductivity than the base material, creating a thermal barrier that reduces heat transfer to the fuel while maintaining structural integrity under high-temperature combustion conditions and repeated loads
2Ease of operation
If the duct is exposed in the combustion chamber, then fuel injection is enabled, but the wall surface temperature of the flow guide passage increases due to heat transfer from high-temperature combustion gases
Solution Approach 1:
A ceramic coating layer is applied as an intermediary between the high-temperature combustion gases and the metal base material. This ceramic layer acts as a thermal barrier with low thermal conductivity, mediating the heat transfer process and maintaining the wall surface temperature at acceptable levels while allowing the duct to remain exposed for fuel 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 configuration enhances the reliability of shape retention and reduces the increase in wall surface temperature, promoting efficient fuel-air mixing and reducing self-ignition, thereby improving thermal efficiency and preventing smoke formation.
Implementation Method 1
the thermal conductivity of the second layer is lower than the thermal conductivity of the first layer. As a result, the heat transferred to the outer wall of the passage wall portion from a high-temperature combustion gas around the passage wall portion can be prevented from being transferred to the inner wall of the passage wall portion
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A compression-ignition internal combustion engine (10) includes a fuel injection nozzle (20) including a tip end portion (20a) exposed in a combustion chamber (12) and a nozzle hole (22) formed at the tip end portion (20a); and a passage forming member (duct 30) forming a flow guide passage (32) through which fuel injected from the nozzle hole (22) passes. The passage forming member includes a passage wall portion (36) located radially outward of the flow guide passage (32). The passage wall portion (36) includes a first layer (36a) that is a base portion connected to a cylinder head (18), and a second layer (36b) located radially outward or radially inward of the first layer (36a). The toughness of the first layer (36a) is higher than the toughness of the second layer (36b). The thermal conductivity of the second layer (36b) is lower than the thermal conductivity of the first layer (36a).