Piston Cooling Chambers for Thermal Stress Reduction
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Solution Overview
Problem
Existing piston designs for internal combustion engines face challenges in effectively managing increased combustion temperatures, with current cooling systems either being inadequate or inefficient, particularly in diesel engines where hot spots lead to undesirable NOx generation and thermal stresses.
Innovation Solution
A piston design featuring a sealed first cooling chamber with a solid cooling medium that melts at a predetermined temperature, combined with an open second cooling chamber for additional heat extraction using cooling oil, which directs heat away from both the piston body and the cooling medium, ensuring uniform cooling and reducing thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single cooling chamber with cooling oil is used, then the piston can be cooled, but the cooling uniformity is insufficient and thermal stresses remain high
Solution Approach 1:
The cooling system is divided into two separate cooling chambers: a first cooling chamber containing a first cooling medium (such as sodium or other metal) and a second cooling chamber containing cooling oil. This segmentation allows different cooling mechanisms to operate in different regions of the piston, achieving more uniform temperature distribution and reducing thermal stresses.
2Use of energy by moving object
If combustion temperature is increased to improve fuel efficiency, then fuel efficiency increases, but the piston cannot withstand the higher temperatures
Solution Approach 1:
The first cooling medium in the first cooling chamber utilizes phase transition (melting/freezing) at a predetermined temperature to absorb and release heat. This phase change mechanism provides intense cooling capability at critical temperature points, enabling the piston to withstand higher combustion temperatures that improve fuel efficiency while maintaining structural integrity.
3Temperature
If a sealed cooling chamber with solid cooling medium is used, then cooling effectiveness increases, but the cooling medium is vulnerable to contaminants and oxidation
Solution Approach 1:
The cooling system separates the solid first cooling medium into a sealed first cooling chamber, protecting it from contaminants and oxidation, while the second cooling chamber with cooling oil provides additional protection and heat extraction. This segmentation allows each cooling medium to be optimized for its specific function while being protected from degradation.
4Temperature
If cooling oil is directed to the portion separating the cooling chambers, then heat extraction from both piston body and first cooling medium improves, but system complexity increases
Solution Approach 1:
The cooling oil in the second cooling chamber serves multiple functions: it cools the piston body directly, cools the first cooling medium through the separating wall, and helps maintain pressure balance between chambers. This multi-functionality increases heat extraction efficiency without requiring separate systems for each cooling function.
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
The dual cooling system allows the piston to operate effectively at higher temperatures, reduces thermal stresses, and minimizes NOx generation by providing uniform cooling, thereby extending the piston's operating life and improving fuel efficiency.
Implementation Method 1
the first cooling medium is of a material which is solid at ambient temperatures and melts at a predetermined temperature corresponding to an improved operating temperature of the engine
Implementation Method 2
contains a first cooling medium other than air for extracting heat from the surrounding regions of the piston body
Implementation Method 3
the cooling oil in the second cooling chamber extracts heat from both the piston body and the first cooling medium
Implementation Method 4
directed to the portion of the piston body separating the first and second cooling chambers to extract heat from the first cooling medium
Data Source
AI summary
A piston for an internal combustion engine including a piston body (20). The piston body (20) defines a first cooling chamber (46) that is sealed closed and contains a first cooling medium (48) other than air. During operation of the piston, the first cooling medium (48) extracts heat from the surrounding regions of the piston body (20) to cool the piston body (20). The piston body (20) also defines a second cooling chamber (50) adjacent to the first cooling chamber (46). A cooling oil (51) is projected into the second cooling chamber (50) and against the portion of the piston body (20) separating the first and second cooling chambers (46, 50) to extract heat from the first cooling medium (48). The cooling oil (51) is redirected within the second cooling chamber (50) to extract additional heat from the first cooling medium (48) or directly from the piston body (20).