Leaf Seal Assembly Asymmetric Design for Bidirectional Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing leaf seals in gas turbine engines face issues such as bristle flexing and wear in brush seals, and failure during reversed pressure gradients in leaf seals, leading to reduced sealing efficiency and potential fluid leakage.
Innovation Solution
A leaf seal assembly with angled, resilient leaf elements and cover plates that flex radially, featuring a larger gap on one side to lift during inflow and a smaller gap on the other side to blow down during outflow, creating an air film and preventing wear, while maintaining sealing efficiency regardless of pressure direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If leaf seal elements are made axially stiff to prevent bending, then sealing direction stability is improved, but tips become damaged and worn by constant contact with rotating shaft
Solution Approach 1:
The leaf elements have different stiffness characteristics at different locations: they are stiffer in the axial direction to maintain sealing direction stability, but more flexible radially to reduce tip wear through controlled deflection. This local differentiation of mechanical properties allows the seal to simultaneously achieve stability and wear resistance
Solution Approach 2:
The constant contact between leaf element tips and the rotating shaft, which causes wear, is converted into a beneficial aerodynamic effect. The relative motion generates a lubricating air film that reduces friction and wear, transforming the harmful contact into a protective mechanism
2Reliability
If leaf seal is designed for pressure gradient in one direction only, then sealing performance is optimized for that direction, but seal fails when pressure gradient reverses causing fluid leakage
Solution Approach 1:
The leaf elements are designed with asymmetric geometry and mounting characteristics that enable them to function effectively under pressure gradients in either direction. The asymmetric design allows the seal to maintain optimal sealing contact whether the high pressure is on the inner or outer side, providing bidirectional sealing capability
Solution Approach 2:
The leaf seal elements are designed to perform multiple sealing functions regardless of pressure gradient direction. The same leaf element structure provides effective sealing whether the pressure gradient is in the original design direction or reversed, making the seal universal and adaptable to varying operating conditions
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 leaf seal assembly effectively prevents wear and fluid leakage across varying pressure gradients, maintaining sealing efficiency and reducing wear on the leaf elements by utilizing lift-up and blow-down behaviors of the leaf elements, effectively acting as a one-way valve.
Implementation Method 1
creating an air film and preventing wear
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a leaf seal assembly 11 for providing a fluidic seal between a first member 30 and a second member 20. The leaf seal assembly comprises first and second cover plates 3, 5 defining a channel 7 therebetween, the first cover plate having a first edge and the second cover plate having a second edge. A plurality of leaf elements 11 are located within the channel, each leaf element having first and second edges 11a, 11b adjacent to the first and second cover plates respectively, and a projecting portion of each leaf element extends beyond the first and second edges of the first and second cover plates. The seal assembly 11 is configured such that when it is located between a first member and a second member, a fluid flow 36 in a first direction from the first cover plate side 3 of the seal assembly to the second cover plate side 5 of the seal assembly causes the plurality of leaf elements 11 to move away from the first member 30 to create a fluid passage between the plurality of leaf elements and the first member, thereby allowing a flow of fluid through the seal in the first direction; and a fluid flow 36 in a second direction from the second cover plate side 5 of the seal assembly to the first cover plate side 5 of the assembly causes the plurality of leaf elements 11 to move towards the first member 30 such that a third edge 11 c of the projecting portion of each of the leaf elements contacts the first member, thereby opposing the flow of fluid through the seal in the second direction.