Ceramic Shroud Assembly with Compliant Interlayer for Gas Turbine Engines
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Solution Overview
Problem
Ceramic shroud rings face challenges in attachment to metal gas turbine engine casings due to differences in thermal expansion coefficients, leading to stress generation and difficulty in minimizing the gap between rotor blade tips and shroud rings, which affects engine performance by increasing gas leakage.
Innovation Solution
A ceramic shroud assembly featuring a metal clamp ring shrink-fitted around the ceramic shroud with a compliant and insulating interlayer, allowing for relative thermal growth and attachment to the metal casing while minimizing stress, and an axial restraint ring to maintain the shroud's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic shroud ring is used to minimize thermal distortion and reduce the gap between rotor blade tips and shroud ring, then engine performance is improved and gas leakage is reduced, but attachment to metal casing becomes difficult due to low ductility and CTE mismatch
Solution Approach 1:
The shroud assembly is segmented into three distinct components: a metal clamp ring, a ceramic shroud ring, and a compliant interlayer. This segmentation allows each material to be optimized for its specific function while avoiding the CTE mismatch problem through physical separation and controlled interfaces.
Solution Approach 2:
A compliant interlayer is introduced as an intermediary between the metal clamp ring and ceramic shroud ring. This interlayer accommodates thermal expansion differences and stress concentrations, enabling reliable attachment of the ceramic shroud to the metal casing without direct metal-to-ceramic contact.
2Ease of manufacture
If a metal clamp ring is shrink fitted around the ceramic shroud to attach it to the metal casing, then attachment is achieved, but thermal stress may generate at the interface due to CTE differences
Solution Approach 1:
The physical and mechanical parameters of the interlayer are specifically selected to match the thermal expansion characteristics of the ceramic shroud. This parameter matching ensures that thermal stresses are minimized at the interfaces during temperature cycling, preventing delamination or failure.
Solution Approach 2:
The compliant interlayer acts as a pre-positioned cushioning element that absorbs and distributes thermal stresses before they can concentrate at the metal-ceramic interfaces. This protective layer prevents stress-induced damage during thermal transients.
3Loss of energy
If the gap between rotor blade tips and shroud ring is minimized to reduce gas leakage, then energy transfer efficiency is improved, but thermal expansion accommodation becomes more difficult
Solution Approach 1:
The shroud assembly incorporates dynamic compliance through the compliant interlayer, allowing the structure to adapt its configuration during thermal transients. This dynamic behavior enables the maintenance of a consistent, minimal gap between blade tips and shroud while accommodating thermal expansion of the rotor and casing.
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 attaches the ceramic shroud to the metal casing, reducing thermal stress and gas leakage, thereby enhancing engine performance by maintaining a consistent and efficient energy transfer from combustion gases to turbine blades.
Implementation Method 1
a metal clamp ring shrink fitted around a ceramic shroud
Implementation Method 2
a compliant and insulating layer positioned between the ceramic shroud and the clamp ring
Data Source
AI summary
A ceramic shroud assembly suitable for use in a gas turbine engine comprises a metal clamp ring shrink fitted around a ceramic shroud ring and an insulating and compliant interlayer. The interlayer is positioned between the metal clamp ring and the ceramic shroud ring.