Segmented Ceramic Layer for Gas Turbine Engine Seals
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Solution Overview
Problem
Conventional abradable ceramic coatings in gas turbine engines are vulnerable to erosion and spalling due to elevated temperatures, leading to increased clearance between turbine blades and outer air seals, which reduces turbine efficiency.
Innovation Solution
A ceramic layer with mechanical indentations is used in the turbine seal member, which reduces internal stresses by providing preexisting locations for energy release, thereby preventing delamination and maintaining engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an abradable ceramic coating is used on the outer air seal to maintain clearance and reduce gas flow leakage, then turbine efficiency is maintained, but the coating becomes vulnerable to erosion and spalling at elevated temperatures
Solution Approach 1:
The ceramic coating is segmented into multiple layers with different functional properties. The first ceramic layer provides thermal barrier properties, while the second ceramic layer provides erosion and spalling resistance. This segmentation allows each layer to address specific temperature-related issues independently, improving overall coating durability without compromising the ability to maintain clearance.
Solution Approach 2:
The invention uses a composite coating structure consisting of multiple ceramic layers with different compositions and properties. The combination of materials creates a coating that simultaneously provides thermal barrier properties, erosion resistance, and spalling prevention, thereby maintaining reliability under elevated temperature conditions while preserving the clearance function.
2Reliability
If the ceramic coating is made thicker to improve protection, then erosion and spalling resistance increases, but internal stresses increase causing delamination
Solution Approach 1:
The coating is divided into multiple thinner layers rather than one thick layer. Each layer can expand and contract independently during thermal cycling, reducing the development of internal stresses that lead to delamination. The segmented structure maintains protection while preserving adhesion through controlled thermal expansion of individual layers.
Solution Approach 2:
The invention changes the thickness parameter of individual coating layers to optimize the balance between protection and stress management. By controlling the thickness of each ceramic layer, the design achieves sufficient protective capability while limiting the accumulation of internal stresses that would cause delamination, thereby maintaining coating strength and adhesion.
3Strength
If the ceramic coating is compacted to reduce porosity and improve density, then coating strength increases, but internal stresses increase leading to spalling
Solution Approach 1:
The coating structure is segmented into multiple layers with different density characteristics. Less dense regions are intentionally created within the coating structure to act as stress relief zones. These segmented density variations allow the coating to maintain overall strength while providing pathways for stress relief, preventing spalling under thermal and mechanical loading.
Solution Approach 2:
The coating is designed with non-uniform local properties, creating regions of different density and porosity within the overall structure. These local quality variations allow certain areas to be more compliant and stress-absorbing, while other areas maintain higher density for strength. This local differentiation prevents uniform stress buildup that would lead to spalling while maintaining overall coating integrity.
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 mechanical indentations in the ceramic layer effectively reduce internal stresses, preventing delamination and maintaining engine efficiency by allowing controlled stress relief, thus enhancing the durability and performance of the turbine seal.
Implementation Method 1
The mechanical indentations provide preexisting locations for releasing energy associated with internal stresses of the ceramic layer
Implementation Method 2
One cause of spalling is the elevated temperature within the turbine section, which causes sintering of a surface layer of the coating. The sintering causes the coating to shrink, which produces stresses between the coating and a substrate of the outer air seal
Data Source
AI summary
A turbine seal member for use in a gas turbine engine includes a turbine seal substrate having a gas-path side and a ceramic layer disposed on the gas-path side that includes a plurality of mechanical indentations.