Floating Ring Seal Structure for Shaft Whirl and Eccentricity
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Solution Overview
Problem
Existing sealing devices for high-speed rotating shafts, such as those in cryogenic liquid fuel turbopumps, fail to effectively reduce shaft vibration and prevent leakage, as they either lack tangential damping or radial restoring forces to counteract eccentricity.
Innovation Solution
A sealing assembly featuring a floating ring with a multi-layered cylindrical body composed of elastically deformable thin plates, arranged in a corrugated shape between the floating ring and the housing, which imparts tangential damping and radial restoring forces to reduce whirling and eccentricity, respectively, while maintaining a sealed fluid gap for efficient pressure generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a floating ring seal is used to prevent leakage, then sealing performance is improved, but shaft vibration is not reduced
Solution Approach 1:
The damping structure is segmented into multiple thin plates (at least two) stacked together, with gaps between them allowing fluid passage. This segmentation enables the structure to provide both sealing support and vibration damping through fluid pressure generation in the gaps, resolving the contradiction between maintaining sealing performance and reducing shaft vibration.
Solution Approach 2:
A damping structure is introduced as an intermediary element between the floating ring and the housing. This intermediary structure generates fluid pressure in the gaps between thin plates to provide tangential damping force, thereby reducing shaft vibration while the floating ring continues to perform its sealing function independently.
2Stability of the object's composition
If leaf springs are added to dampen floating ring vibration, then floating ring stability is improved, but shaft vibration reduction is not achieved
Solution Approach 1:
Instead of using mechanical leaf springs, the invention employs a hydraulic/pneumatic damping mechanism where fluid pressure generated in the gaps between thin plates provides the damping force. This fluid-based approach generates tangential damping force that directly counteracts shaft whirling, effectively reducing shaft vibration while maintaining floating ring stability.
Solution Approach 2:
The invention changes the damping mechanism from mechanical spring deformation to fluid pressure generation. By utilizing fluid compressibility and viscosity in the gaps between thin plates, the system generates damping forces that address shaft vibration directly, rather than only supporting the floating ring.
3Stability of the object's composition
If support means are added to prevent alignment issues, then floating ring alignment is improved, but shaft vibration reduction is not achieved
Solution Approach 1:
The support structure is segmented into multiple thin plates with gaps between them, allowing the structure to simultaneously provide alignment support and generate fluid pressure for vibration damping. The segmented design enables dual functionality that single-structure support means cannot achieve.
Solution Approach 2:
The multi-layered cylindrical body with gaps between thin plates serves multiple functions: it supports the floating ring radially, provides tangential damping force to reduce shaft vibration, and allows fluid passage for pressure generation. This multi-functional design resolves the contradiction by making the support structure itself the vibration damping mechanism.
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 solution effectively reduces shaft vibration and prevents leakage by providing consistent radial restoring and tangential damping forces, ensuring the rotating shaft remains centered and sealed, with the corrugated shape and metallic material enhancing durability and production ease.
Implementation Method 1
a multi-layered cylindrical body including a plurality of elastically deformable cylindrical thin plates layered on top of each other provided between an outer peripheral surface of the floating ring and an inner peripheral surface of the housing
Implementation Method 2
imparting a tangential damping force to reduce the whirling of the rotating shaft
Implementation Method 3
maintain a constant clearance between the inner peripheral surface of the floating ring and the rotating shaft by the wedge effect generated between the inner peripheral surface of the floating ring and the rotating shaft (the effect of dynamic pressure generated at a wedge portion)
Implementation Method 4
the Lomakin effect (the aligning effect due to inflow losses between the surfaces of the seal ring and the shaft when seal differential pressure develops)
Data Source
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AI summary
To impart a radial restoring force against the eccentricity of a rotating shaft to restore it to its center position, and a tangential damping force to reduce the whirling of the rotating shaft. A sealing device includes a floating ring 5 in a space 4 between the outer circumference of a rotating shaft 3 and the inner circumference of a housing 2, and a multi-layered cylindrical body 10 including a plurality of elastically deformable cylindrical thin plates 11 layered on top of each other provided between an outer peripheral surface of the floating ring 5 and an inner peripheral surface of the housing.