Piston Crown Thermal Management via Layered Heat Diffusion
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Solution Overview
Problem
In homogeneous-charge compression-ignition and spark-ignition combustion engines, the heat-insulation layer can store excessive heat, leading to increased cylinder internal temperature and potential preignition issues, especially during high-load engine operations.
Innovation Solution
A piston combustion-chamber structure with a heat-barrier layer, a heat-insulation layer, and a heat-diffusion layer is implemented, where the heat-diffusion layer has higher conductivity than both the heat-insulation and heat-barrier layers, allowing heat stored in the heat-insulation layer to escape to the piston body, thereby preventing excessive temperature increase of the heat-barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a heat-insulation layer is provided at the central area of the piston crown surface to reduce heat loss and enable controlled combustion, then heat loss is reduced and combustion is controlled, but the heat-insulation layer stores excessive heat during high-load operations, causing cylinder internal temperature increase and potential preignition
Solution Approach 1:
The piston crown surface is segmented into multiple functional layers: a heat-barrier layer covering the entire crown surface to reduce heat loss, a heat-insulation layer at the central area to control combustion initiation, and a heat-diffusion layer between them to manage heat distribution. This segmentation allows each layer to perform its specific function while working together to resolve the contradiction between heat loss reduction and temperature control.
Solution Approach 2:
The heat-diffusion layer acts as an intermediary between the heat-insulation layer and the heat-barrier layer. It receives heat from the heat-insulation layer and diffuses it laterally, preventing excessive heat accumulation that would otherwise transfer to the heat-barrier layer and cause preignition. This intermediary layer resolves the contradiction by controlling the heat flow path.
2Loss of energy
If a heat-barrier layer covers the entire piston crown surface to suppress heat dissipation, then heat loss is reduced, but the heat-barrier layer temperature increases excessively during high-load operations, causing improper preignition
Solution Approach 1:
The heat-barrier layer is segmented into multiple layers with different thermal properties: the heat-insulation layer at the center for controlled heat storage and the heat-diffusion layer as an intermediary to prevent excessive heat transfer to the outer heat-barrier layer. This segmentation allows the heat-barrier layer to maintain its heat dissipation suppression function while preventing temperature-induced preignition.
Solution Approach 2:
The heat-diffusion layer serves as a protective intermediary between the heat-insulation layer and the heat-barrier layer. It prevents excessive heat from the heat-insulation layer from transferring to the heat-barrier layer, thereby protecting the heat-barrier layer from temperature increase that would cause preignition while maintaining its heat dissipation suppression function.
3Productivity
If homogeneous-charge compression-ignition combustion is used to improve fuel economy and exhaust purification, then fuel economy and exhaust purification are improved, but cylinder internal pressure increases rapidly causing large combustion noise and mechanical load
Solution Approach 1:
The heat-insulation layer is localized at the central area of the piston crown surface, creating a local high-temperature zone that initiates combustion at a specific location. This local quality approach transforms the concurrent combustion of homogeneous-charge compression-ignition into a more controlled, progressive combustion wave, reducing the rapid pressure increase while maintaining the fuel economy benefits.
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 reduces heat loss and prevents preignition by maintaining a temperature difference between combustion gases and the piston crown surface, ensuring efficient combustion and reducing mechanical load on engine components.
Implementation Method 1
a heat-diffusion layer which is provided between the heat-insulation layer and the heat-barrier layer and has larger heat conductivity than the heat-insulation layer and the heat-barrier layer
Implementation Method 2
a heat-barrier layer which is provided to cover the upper surface of the piston and has smaller heat conductivity than the piston body... a heat-insulation layer which is provided at least in a central area, in a radial direction, of the upper surface of the piston body and has smaller heat conductivity than the piston body
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A combustion chamber is partitioned by a cylinder block, a cylinder head, and a piston. The piston includes a piston body having an upper surface facing the combustion chamber, a heat-insulation layer provided at least in a central area, in a radial direction, of the upper surface and having smaller heat conductivity than the piston body, a heat-barrier layer provided to cover the upper surface and having smaller heat conductivity than the piston body and the heat-insulation layer, and a heat-diffusion layer provided between the heat-insulation layer and the heat-barrier layer and having larger heat conductivity than the heat-insulation layer and the heat-barrier layer. The heat-diffusion layer comprises a side end edge and an extension portion which contact with the piston body.