Segmented Non-Contact Seal Assembly for Low-Stress Annular Gap Sealing
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Solution Overview
Problem
Existing rotational equipment seal assemblies for gas turbines and similar equipment face challenges in effectively sealing annular gaps between rotors and stationary structures, leading to inefficiencies and potential leaks.
Innovation Solution
A non-contact seal assembly featuring a primary hydrostatic seal device with seal shoes and resilient biasing elements, along with secondary seal devices, is designed to seal the annular gap between the rotor and stationary structure, utilizing a press fit connection and spring elements to maintain sealing within predetermined design tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional seal assemblies are used to seal the annular gap, then sealing function is provided, but internal stress is high and manufacturing costs increase
Solution Approach 1:
The seal assembly is divided into multiple independent seal shoes (typically 3-6 shoes spaced circumferentially) rather than a continuous seal structure. Each seal shoe is independently supported by resilient biasing elements, allowing stress distribution and reducing internal stress while maintaining effective sealing of the annular gap between the rotor and stationary structure.
Solution Approach 2:
The seal shoes are made dynamically responsive through the resilient biasing elements (springs) that allow each shoe to independently adjust its position radially. This dynamic capability enables the seal to adapt to varying operational conditions, reducing stress concentrations while maintaining sealing effectiveness under different pressure and temperature conditions.
2Reliability
If conventional seal assemblies are used to seal the annular gap, then sealing function is provided, but manufacturing costs increase
Solution Approach 1:
The segmented design with discrete seal shoes and resilient biasing elements simplifies manufacturing compared to complex continuous seal structures. Each component can be manufactured independently using standard machining processes, and the modular assembly facilitates easier quality control and reduced manufacturing costs while maintaining reliable sealing.
Solution Approach 2:
The resilient biasing elements are designed to automatically adjust and maintain optimal sealing contact between the seal shoes and the rotor surface without requiring external control systems or complex adjustment mechanisms. This self-regulating feature reduces manufacturing complexity and costs while ensuring consistent sealing performance.
3Reliability
If seal shoes are biased toward the rotor surface, then sealing is maintained, but natural frequency decreases
Solution Approach 1:
By segmenting the seal into multiple independently biased shoes, each shoe can be optimized with lighter mass and appropriate spring stiffness. This segmentation allows the system to maintain sealing contact while achieving higher natural frequencies for each individual shoe, reducing the risk of resonance and vibration issues.
Solution Approach 2:
The resilient biasing elements are designed with specific stiffness parameters that optimize the balance between maintaining sealing contact and achieving adequate natural frequency. By carefully selecting spring constants and shoe masses, the system maintains reliable sealing while ensuring natural frequencies are sufficiently high to avoid operational resonance.
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 provides a robust and efficient sealing mechanism that reduces internal stress and manufacturing costs, while maintaining high natural frequency and effectively sealing the annular gap, even under varying operational conditions.
Implementation Method 1
a plurality of spring elements arranged circumferentially about the axis and radially between the seal shoes and the seal base, each spring element configured to moveably connect a respective one of the seal shoes to the seal base
Implementation Method 2
a primary hydrostatic seal device with seal shoes and resilient biasing elements
Data Source
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AI summary
A seal device (40) includes a plurality of seal shoes (54), a seal base (52), a plurality of spring elements (56) and a resilient biasing element (57). The seal shoes (54) are arranged around an axis (22). The seal base (52) circumscribes the seal shoes (54). Each of the spring elements (56) is radially between and connects a respective one of the seal shoes (54) and the seal base (52). A first of the spring elements (56) includes a first mount (78), a second mount (80) and a spring beam (82). The first mount (78) is connected to a first of the seal shoes (54). The second mount (80) is connected to the seal base (52). The spring beam (82) connects the first mount (78) to the second mount (80). The resilient biasing element (57) is radially between and engaged with first and second components of the seal device (40), where the first component is configured as or otherwise includes the first mount (78) or the second mount (80).