Segmented Hydrodynamic Face Seal for Large Rotary Machines
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Solution Overview
Problem
Existing rotary machines face challenges with fluid leakage due to limitations in sealing assemblies, particularly with large diameter shafts where known hydrodynamic face seals are unsuitable due to size constraints and thermal coning issues, and labyrinth teeth wear out over time, reducing efficiency.
Innovation Solution
A multiple layer, segmented hydrodynamic face seal ring system comprising a support ring and sealing ring with radially-extending faces, allowing for easy assembly and disassembly on large diameter shafts, and featuring segmented construction to mitigate thermal coning and size limitations, with a seal housing that moves with the sealing ring to maintain a thin fluid film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single continuous seal ring is used, then sealing effectiveness is improved, but manufacturing difficulty and assembly complexity increase for large diameter shafts
Solution Approach 1:
The seal ring is divided into multiple segments that can be manufactured separately and assembled together using mechanical fasteners. This segmentation allows each segment to be manufactured with controlled dimensions and flatness, avoiding the manufacturing difficulties of large single-piece rings while maintaining sealing effectiveness through the combined segments.
2Manufacturing precision
If a single continuous seal ring is used, then sealing face flatness can be maintained, but thermal coning increases with the fourth power of diameter
Solution Approach 1:
Dividing the seal ring into segments interrupts the continuous thermal path, preventing the accumulation of thermal gradients across large diameters. Each segment experiences reduced thermal coning individually, and the segmented construction allows for thermal expansion compensation at the joints, maintaining sealing face flatness despite temperature variations.
3Ease of operation
If the seal ring is segmented, then assembly on large diameter shafts is facilitated, but a step over the segment joint may be larger than the film thickness
Solution Approach 1:
The sealing surfaces of the segments are pre-machined to high flatness tolerances before assembly. Alignment features and precision fastening mechanisms are built into the segment design to ensure that when assembled, the sealing faces maintain the required flatness and minimize step heights, preventing interference with the hydrodynamic film.
4Reliability
If labyrinth teeth are used, then sealing is provided, but the teeth wear out over time due to contact with the rotary component
Solution Approach 1:
The patent replaces the mechanical contact-based labyrinth teeth sealing mechanism with a hydrodynamic face seal that relies on fluid pressure and hydrodynamic forces. This substitution eliminates direct mechanical contact between stationary and rotating components, preventing wear and extending service life while maintaining sealing effectiveness.
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 significantly reduces fluid leakage in rotary machines by maintaining a thin fluid film and ensuring proper sealing, enhancing the assembly and maintenance of large diameter face seal rings, thereby improving the overall performance and efficiency of rotary machines.
Implementation Method 1
During operation, grooves in the rotating ring generate a hydrodynamic force that causes the stationary ring to lift or separate from the rotating ring such that a small gap is created between the two rings
Data Source
AI summary
A hydrodynamic face seal ring for use in a rotary machine includes a support ring having at least two support ring segments and a radially-extending, first face. The support ring is configured to releasably couple to an inner surface of an outer casing of the rotary machine. The face seal ring also includes a sealing ring substantially concentric with the support ring. The sealing ring includes at least two sealing ring segments and a radially-extending, second face. The sealing ring is releasably coupled to the support ring such that the first face is mated against the second face.