Overlapping Compression Ring Ends for Gas-Tight Wear Control
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Solution Overview
Problem
Existing 2-stroke crosshead engines face severe abrasive wear on compression ring sealing surfaces due to combustion gas entering through axial and radial gaps, leading to delamination and system failure, with complex manufacturing and thermal expansion issues complicating the use of precision sealing structures.
Innovation Solution
A compression ring design featuring overlapping butt end regions with projections and recesses, incorporating wear elements made of low-wear resistance materials, allowing parallel displacement to minimize wear and maintain a gas-tight seal despite thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the axial and radial gaps are kept small to prevent combustion gas entry, then sealing performance is improved, but manufacturing complexity and rejection rates increase due to warping during grinding
Solution Approach 1:
The compression ring is segmented into overlapping butt end regions with projections and recesses, creating multiple sealing surfaces (axial and radial overlap surfaces) that work together to prevent gas leakage. This segmentation allows the sealing function to be distributed across multiple surfaces rather than relying on a single precise gap dimension.
Solution Approach 2:
The wear elements are applied to the overlap surfaces before the ring is installed in the engine. During initial operation, these wear elements undergo controlled wear to establish the precise final dimensions of the sealing surfaces, eliminating the need for extremely precise initial manufacturing of the gap dimensions.
2Reliability
If precision sealing structures are used to minimize gaps, then gas-tight sealing is improved, but thermal expansion during operation leads to increased wear and potential destruction
Solution Approach 1:
Wear elements are applied to the overlap surfaces to provide a cushioning layer that absorbs the effects of thermal expansion. These sacrificial wear elements prevent direct contact and wear between the hard sealing surfaces during thermal cycling, protecting the precision sealing geometry from thermal distortion damage.
Solution Approach 2:
The wear elements are designed as consumable components with lower material strength than the base ring. They are intended to wear down during initial operation to establish precise sealing dimensions, after which they are replaced or the ring is reconditioned. This disposable approach protects the expensive precision sealing surfaces from wear.
3Reliability
If wear elements with low wear resistance are applied to overlap surfaces, then wear protection is improved, but material selection becomes more constrained by temperature resistance requirements
Solution Approach 1:
The invention changes the material parameter selection criterion from prioritizing wear resistance to prioritizing temperature resistance. Wear elements are selected from materials like copper, tin, bronze, or their alloys, which have sufficient wear resistance for the application but are primarily selected based on their ability to withstand engine operating temperatures without softening or degrading.
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 effectively reduces wear on compression rings by allowing parallel movement of overlapping surfaces, maintaining a tight seal and minimizing abrasive wear, thus preventing delamination and extending the engine's operational lifespan.
Implementation Method 1
at least one of the surfaces displaceable parallel to one another is provided with an axial wear element and/or with a radial wear element
Implementation Method 2
the thermal expansion of the rings and cylinders during operation must be taken into account
Data Source
Figure 1~2
AI summary
The invention relates to a compression ring comprising a ring running surface (2) on a first butt end region, a ring running surface (2') on a second butt end region, a ring inner surface (4), a top ring flank surface (6) and a bottom ring flank surface (8), wherein: the ring has overlapping butt end regions; the first butt end region has at least one protrusion (10) in the circumferential direction, and the second butt end region has at least one recess (12) in the circumferential direction; the at least one protrusion (10) forms at least one axial and/or radial overlap surface, and the at least one recess (12) forms at least one surface that is at least partially opposite and parallel to the axial and/or radial overlap surface in order to move parallel to one another when the butt play changes; and at least one of the surfaces that can move parallel to one another is furnished with an axial wear element (14) and/or with a radial wear element (14').