Laminated Ceramic Sealing Tabs for Turbine Sector Joints
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Solution Overview
Problem
The existing sealing tabs in turbomachines made of nickel-based or cobalt-based alloys react with ceramic matrix composite (CMC) materials at high temperatures, leading to chemical diffusion and degradation, necessitating a solution that prevents such reactions while maintaining mechanical strength and flexibility.
Innovation Solution
The use of laminated sealing tabs with upper and lower blades made of chemically inert monolithic ceramic material, optionally with intermediate metallic blades, to avoid chemical reactions and enhance flexibility, allowing the tabs to adapt to groove shapes without risk of breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nickel-based or cobalt-based alloy sealing tabs are used, then mechanical strength and high-temperature resistance are improved, but chemical reactions and degradation with CMC material occur at high temperatures
Solution Approach 1:
A protective coating layer is applied to the sealing tab surface to act as an intermediary barrier. This coating prevents direct contact and chemical reactions between the metal alloy and CMC material while allowing the metal substrate to maintain its mechanical strength properties.
Solution Approach 2:
The sealing tab is designed as a composite structure combining metal alloy substrate with a protective coating layer. This composite approach allows the metal to provide mechanical strength while the coating prevents harmful chemical reactions with CMC material at high temperatures.
2Object-affected harmful factors
If monolithic ceramic material sealing tabs are used, then chemical inertness with CMC material is improved, but flexibility and resistance to deformations deteriorate
Solution Approach 1:
The sealing tab uses a composite structure with a flexible metal alloy substrate providing mechanical strength and flexibility, while a chemically inert protective coating layer prevents reactions with CMC material. This combines the advantages of both materials.
Solution Approach 2:
The protective coating is applied as a thin film on the metal substrate, allowing the overall structure to maintain flexibility while providing chemical protection. The thin film architecture enables deformation accommodation without compromising the protective function.
3Adaptability or versatility
If laminated structure with thin ceramic films is used, then flexibility and adaptability to groove shapes are improved, but risk of breakage increases
Solution Approach 1:
The laminated thin ceramic films are bonded to a flexible metal substrate, creating a composite structure where the metal provides structural support and prevents breakage while the thin ceramic layers provide chemical protection and flexibility for groove adaptation.
Solution Approach 2:
Multiple thin ceramic films are laminated in a flexible configuration, allowing the structure to bend and adapt to groove shapes. The thin film architecture, when supported by a flexible substrate, reduces brittleness while maintaining adaptability.
4Reliability
If sealing tabs are housed in grooves machined in CMC connecting edges, then sealing is achieved, but chemical diffusion and degradation occur at high temperatures
Solution Approach 1:
The protective coating on the sealing tab acts as an intermediary barrier between the metal tab and the CMC groove material. This coating prevents chemical diffusion and reactions at the interface while allowing the sealing function to operate effectively in the high-temperature environment.
Solution Approach 2:
The close contact between sealing tab and groove is converted from a harmful situation (chemical reactions) to a beneficial one (effective sealing) by applying a protective coating. The same interface that could cause chemical diffusion becomes a sealed interface when protected by the inert coating layer.
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 effectively prevents high-temperature chemical reactions between sealing tabs and CMC materials, ensuring reliable sealing and resistance to deformations, thereby maintaining the structural integrity and performance of turbomachine components.
Implementation Method 1
each sealing tab has a laminated structure which gives it greater flexibility and, consequently, good resistance to deformations encountered in operation and/or to adapt to the shape of the groove
Implementation Method 2
The parts of the sealing tab(s) intended to be in contact with the CMC of the assembly sectors, namely the lower and upper faces, are made of a film of ceramic material which is chemically inert with respect to the CMC material
Data Source
Figure 1A
Figure 1B~2A
Figure 2B~3
AI summary
An assembly for a turbine comprises a plurality of sectors (40) which are adjacent to one another, each actor comprising at least one connecting edge (42, 43) of composite material with a ceramic matrix, each connecting edge comprising at least one groove (420, 421, 422) and a sealing tongue (150, 151, 152) present in each groove. Each sealing tongue has a laminated structure comprising a plurality of strips (101, 102, 103, 104, 105, 106, 107, 108, 109, 110), the lower strip (101) and the upper strip (110) of the laminated structure each being formed by a film of monolithic ceramic material.