Face Seal Assembly With Isolated Hydrostatic Ports
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Solution Overview
Problem
Turbomachines face challenges in maintaining high fluid-film stiffness and tolerance with increasing rotor and seal ring diameters, as well as dealing with thermal and pressure deformations and angular misalignments, which traditional face seal assemblies are unable to effectively address.
Innovation Solution
A face seal assembly incorporating isolated hydrostatic ports and hydrodynamic elements that generate a thick fluid-film, providing high stiffness and self-adjustment capabilities to accommodate misalignments and deformations, while reducing machining costs through lower flatness requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the sealing ring and rotor is increased, then the turbomachine capacity is improved, but the machining cost and difficulty increase due to the requirement of high degree of flatness
Solution Approach 1:
The invention changes the operating parameter from thin fluid-film (2-10 microns) to thick fluid-film (25-100 microns), which relaxes the flatness requirement and machining tolerance, thereby reducing machining cost while maintaining seal effectiveness
Solution Approach 2:
The invention uses hydrostatic pressure (orifice-compensated system) to maintain the fluid-film between sealing faces, replacing the need for tight mechanical tolerances and high flatness with a pressure-controlled hydraulic film that accommodates larger dimensions
2Ease of manufacture
If the fluid-film thickness is increased to reduce machining requirements, then the manufacturing cost is reduced, but the fluid-film stiffness decreases
Solution Approach 1:
The invention employs orifice compensation that provides feedback control of the fluid-film thickness through pressure-sensitive flow restriction, automatically adjusting the film thickness to maintain optimal stiffness while operating with thicker films
Solution Approach 2:
The hydrostatic orifice-compensated system uses hydraulic pressure feedback to regulate the fluid-film thickness, maintaining high stiffness through pressure control rather than relying solely on mechanical tolerances
3Device complexity
If traditional hydrodynamic face seal is used, then the structure is simple, but the sealing effectiveness deteriorates under thermal and pressure loads due to face deformation
Solution Approach 1:
The invention transitions from hydrodynamic to hydrostatic (orifice-compensated) sealing, using pressurized fluid delivery to maintain reliable sealing under thermal and pressure loads, compensating for face deformation and coning effects
Solution Approach 2:
The invention changes from thin fluid-film hydrodynamic operation to thick fluid-film hydrostatic operation, which provides greater tolerance for thermal and pressure-induced deformations 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 achieves improved dynamic stability and increased operating margins by maintaining high fluid-film stiffness and thickness, allowing for larger rotor and seal ring diameters with reduced machining costs and enhanced misalignment tolerance.
Implementation Method 1
a face seal assembly including a seal ring including a seal bearing face, a first pressure cavity, and a plurality of isolated hydrostatic ports extending from the first pressure cavity to the seal bearing face
Implementation Method 2
a fluid-film of a pressurized fluid may separate the sealing faces from each other and prevent wear due to friction
Implementation Method 3
The fluid-film may further reduce the leakage flow of the process fluid there between the sealing faces
Data Source
AI summary
A turbomachine and a method of operating the turbomachine are disclosed. The turbomachine includes a stator, a rotor including a rotor bearing face, a face seal assembly, a first pressure cavity, and a second pressure cavity. The face seal assembly includes a seal ring including a seal bearing face, a first pressure cavity, and a plurality of isolated hydrostatic ports extending from the first pressure cavity to the seal bearing face. The face seal assembly is slidably coupled to the stator and defines a face seal clearance between the rotor and seal bearing faces. The second and third pressure cavities are defined by the stator, the rotor, and the face seal assembly. The third pressure cavity is disposed downstream of the second pressure cavity with reference to flow of a process fluid along the stator and rotor. The first pressure cavity is isolated from the second and third pressure cavities.