Convex Piston Ring Partition for Gap-Area Sealing in Two-Stroke Engines
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Solution Overview
Problem
Existing piston ring designs for large two-stroke turbo-charged uniflow-scavenged crosshead engines suffer from insufficient sealing in the gap area, leading to leakage, overheating, and coating damage due to the aggressive combustion environment, which results in blow-by and ring collapse.
Innovation Solution
A piston ring design with a convex outer surface and controlled leakage grooves, featuring a ring partition with a circumferential extent of at least 10-20 degrees from the gap area, ensuring a wider sealing area and improved material properties through laser cladding, thereby enhancing sealing effectiveness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrel-shaped profile with uniform radius of curvature is used on the outer ring surface, then the sealing area is distributed evenly, but the sealing effectiveness in the gap area is insufficient leading to leakage and overheating
Solution Approach 1:
The patent applies local quality by providing different radius of curvature values in different circumferential zones of the outer ring surface. Specifically, the gap area has a smaller radius of curvature (R1) compared to other areas (R2), creating locally optimized sealing characteristics in the critical gap region while maintaining overall sealing performance.
Solution Approach 2:
The patent utilizes spheroidality by employing a barrel-shaped profile with controlled curvature variations. The outer ring surface features a rounded contour with specific radius of curvature values that optimize contact pressure distribution and sealing effectiveness, particularly in the gap area where enhanced curvature (smaller R1) improves sealing without causing leakage or overheating.
2Reliability
If the ring gap area is reduced to improve sealing, then leakage is reduced, but the temperature in the gap area increases leading to coating peel-off and ring collapse
Solution Approach 1:
The patent applies local quality by implementing zone-specific radius of curvature values where the gap area has radius R1 and other areas have radius R2. This local differentiation allows optimized sealing in the gap region while controlling temperature through appropriate curvature selection, preventing the overheating that leads to coating failure and ring collapse.
3Reliability
If the circumferential extent of the ring partition is increased to improve sealing, then sealing effectiveness improves, but the complexity of the ring design increases
Solution Approach 1:
The patent applies local quality by implementing zone-specific radius of curvature values (R1 for gap area, R2 for other areas) rather than uniform curvature throughout. This localized differentiation improves sealing effectiveness in the critical gap region while maintaining a relatively simple overall ring partition design that does not excessively increase manufacturing 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 achieves superior sealing in the gap area, reducing the risk of coating peel-off and blow-by, maintaining consistent flat profiles, and distributing pressure evenly across the ring circumference to prevent overheating and ring collapse.
Implementation Method 1
The outer ring surface (12) of the piston ring (4, 6) slides against an inner side of a cylinder liner (7)
Implementation Method 2
The piston ring (4, 6) seal against the pressure in a combustion chamber (2) above the piston (1)
Implementation Method 3
improved material properties through laser cladding
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A piston ring (4, 6) for use in a piston ring pack in an annular ring groove (3) in the sidewall of a piston (1) of a large two-stroke turbo-charged uniflow-scavenged crosshead internal combustion engine to seal against the pressure in a combustion chamber (2) above the piston (1), the piston ring (4, 6) having a ring body (11), a diameter (22), a height (21), an upper ring surface (22), a lower ring surface (23), an outer ring surface (12) and an inner ring surface (24), which outer ring surface (12) during operation of the engine slides against an inner side of a cylinder liner (7), and first- and second engaging end portions (8, 9) at a ring partition (10) that allows expansion and contraction of the piston ring (4, 6), where the first engaging end portion (8) comprises a circumferentially extending finger (13) and the second engaging end portion (9) comprises an circumferentially extending recess (14) shaped and sized for displaceably receiving the finger (13), where a gap area (15) is provided at the end of the finger (13), in which gap area (15) only the end portion (9) with the recess (14) constitutes part of the outer ring surface (12) sliding against the cylinder liner (7). The outer ring surface (12) of the piston ring (4, 6) at least in said ring section (10), as seen in cross section, is convex and part of a imaginary circle having a center (20) and a radius of curvature (25) of a least 0,8 times, preferably at least 1 times the diameter of the piston ring (4, 6). Hence, it will be possible to obtain an effective sealing in the gap area (15), where problems related to coating damages and blow by of combustions gases from the combustion chamber (2) above the piston (1) are avoided. By providing the ring section (10) with an outer surface (12) as defined above it is ensured that the sliding surface (12) of the piston ring (4, 6) which provides the sealing effect also includes a sufficient part of the end portion (9) with the recess (14) in the gap area (15) to ensure a proper sealing effect also in this gap area (15).