Piston Crown Cooling Jet for Under-Crown Heat Management
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Solution Overview
Problem
Diesel pistons face challenges in effectively cooling the under-crown region, leading to carbon build-up, imbalance, and excessive heat, which affects exhaust emissions and lubricating oil degradation.
Innovation Solution
A piston design featuring an outer cooling gallery with an oil inlet and outlet, and an oil jet that circulates oil from the gallery to the under-crown region, ensuring adequate cooling without overheating the oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a central cooling gallery is used to cool the under-crown region, then cooling effectiveness is improved, but the oil becomes overheated and deteriorates
Solution Approach 1:
The cooling gallery is divided into two separate galleries: an outer cooling gallery for cooling the ring belt region and an inner cooling gallery for cooling the under-crown region. This segmentation allows independent oil flow control to each region, preventing the oil from being overheated by the extreme heat of the under-crown region while still providing adequate cooling.
Solution Approach 2:
Different cooling strategies are applied to different regions: the outer gallery provides cooling to the ring belt region with moderate heat exposure, while the inner gallery provides targeted cooling to the under-crown region. The oil flow paths are optimized locally for each region's specific thermal requirements, allowing effective cooling without excessive oil heating.
2Temperature
If oil flow to the under-crown region is increased, then cooling effectiveness is improved, but oil circulation time increases causing overheating
Solution Approach 1:
The cooling system is segmented into separate oil circulation paths: oil flows through the outer gallery for ring belt cooling and through the inner gallery for under-crown cooling. This segmentation creates independent, optimized flow paths that reduce overall oil circulation time by eliminating redundant flow through regions that don't require intensive cooling.
Solution Approach 2:
The cooling intensity is optimized for each region's specific needs rather than applying uniform excessive cooling throughout. The inner gallery provides targeted partial cooling to the under-crown region where it is most needed, while the outer gallery handles the less intensive ring belt cooling, overall reducing the time oil remains in the system.
3Device complexity
If a single outer cooling gallery is used, then device complexity is reduced, but under-crown region cooling effectiveness is insufficient
Solution Approach 1:
The cooling system is segmented into two distinct galleries: an outer cooling gallery and an inner cooling gallery, each serving specific regions. This segmentation provides the necessary cooling effectiveness for the under-crown region while maintaining a relatively simple overall structure that can be manufactured as an integrated piston component.
Solution Approach 2:
The dual gallery configuration serves multiple cooling functions simultaneously: the outer gallery cools the ring belt region while the inner gallery cools the under-crown region. This multi-functional design addresses different thermal management needs within a unified piston structure, achieving comprehensive cooling without excessive complexity.
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 design provides enhanced cooling to the under-crown region, preventing carbon build-up and maintaining the lubricating oil's effectiveness, thereby improving engine efficiency and reducing emissions.
Implementation Method 1
the normal engine lubricating oil is used to help cool (convectively) the hot head, or specifically the under-crown region, of the piston
Data Source
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AI summary
A piston (10, 10') includes a piston body (12, 12') having an upper crown portion (16, 16') with an upper combustion dome (18, 18') against which combustion forces act. The underside of the upper combustion dome (18, 18') comprises an under-crown region (60, 60'). The piston body (12, 12') also includes a lower crown portion (26, 26') with a pair of pin bosses (36, 38) spaced apart for pivotally adjoining a connecting rod. An outer oil gallery (31, 31 ') is formed as an inclusion between the upper (16, 16') and lower (26, 26') crown portions. The outer oil gallery (31, 31 ') has an oil inlet (50, 50') and an oil outlet (52, 52'). A tubular oil jet (54, 54') is affixed in fluid communication with the oil outlet (52, 52') and extends toward the under-crown region (60, 60') where oil is discharged during reciprocation of the piston (16, 16'). Cooling oil from the outer oil gallery (33) is channeled by the oil jet (54, 54') to the under-crown region (60, 60') providing supplemental cooling in a passively actuated system.