Polymer Leaf Seal Assembly for Rotary Machine Leakage
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Solution Overview
Problem
Inter-leaf leakage occurs between metallic leaf seal members of successive seal element layers in rotary machines, which affects the efficiency and performance of seals in turbo machinery.
Innovation Solution
A seal assembly is designed with a plurality of staggered metallic leaf seal members and a polymer top member on the high-pressure side, where the polymer member is in compliant contact with the leaf seals, minimizing inter-leaf leakage by using a continuous polymer top seal element made of materials like PTFE, which is effective up to 500° F, eliminating inter-leaf leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic leaf seal members are used to create seal elements, then the seal can withstand differential pressure and provide structural support, but inter-leaf leakage occurs between successive seal element layers
Solution Approach 1:
The patent combines metallic leaf seal members with polymer materials to create a composite seal structure. The metallic leaves provide structural strength and differential pressure resistance, while the polymer material fills the gaps between leaves to eliminate inter-leaf leakage. This composite approach resolves the contradiction by integrating the advantages of both materials.
Solution Approach 2:
The polymer material acts as an intermediary substance between the metallic leaf seal members. It fills the spaces and gaps between the leaves, preventing fluid leakage while allowing the metallic structure to maintain its load-bearing function. This intermediary material solves the leakage problem without compromising the structural integrity provided by the metal leaves.
2Reliability
If polymer materials are used for sealing, then inter-leaf leakage is eliminated, but the seal may not withstand high differential pressures and temperatures
Solution Approach 1:
The patent creates a composite structure where polymer material is applied to or between metallic leaf seal members. The polymer provides continuous sealing to eliminate leakage, while the metallic framework maintains the ability to withstand high differential pressures and temperatures. This composite material approach allows both sealing effectiveness and structural strength to coexist.
Solution Approach 2:
The patent applies polymer material specifically in the regions where sealing is needed (between and around the leaf edges) while maintaining the metallic structure in areas requiring strength and pressure resistance. This localized application of different materials optimizes both sealing effectiveness and mechanical strength according to the specific functional requirements of each region.
3Reliability
If continuous polymer top seal element is used, then inter-leaf leakage is minimized, but manufacturing complexity increases
Solution Approach 1:
The polymer top seal element can be designed as a separate, replaceable component that is relatively simple to manufacture and install. While it may require periodic replacement, its simple construction and ease of installation offset the initial assembly complexity. The polymer component can be molded as a single piece, reducing manufacturing steps compared to creating precise metal-to-metal interfaces.
Solution Approach 2:
The composite structure allows the polymer sealing element to be manufactured separately from the metallic leaf assembly, then combined through relatively simple bonding or fitting procedures. This modular composite approach reduces overall manufacturing complexity compared to attempting to create a fully integrated metal seal with complex inter-leaf interfaces.
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 seal assembly significantly reduces shaft seal leakage in rotary machines by utilizing a continuous polymer top member that is compliant with metallic leaf seal elements, ensuring effective sealing across a wide range of operating temperatures and pressures.
Implementation Method 1
a polymer member disposed on a high pressure side of the leaf seal, wherein the polymer member is in compliant contact with the leaf seal
Data Source
AI summary
A seal assembly which, among other applications, may be used for sealing fluid leakage between low temperature multistage compressors and pumps, steam turbine rotors and turbine stator bodies. In one embodiment, a seal assembly is provided that includes a leaf seal including a plurality of staggered leaf seal members; and a polymer member disposed on a high pressure side of the leaf seal, wherein the polymer member is in compliant contact with the leaf seal.