Low-Ductility Turbine Shroud Mounting via Load Spreader
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Solution Overview
Problem
Conventional methods for mounting metallic shrouds in gas turbine engines are not suitable for low-ductility materials like ceramic matrix composites (CMCs) due to their low tensile ductility and different thermal expansion characteristics, which can lead to excessive concentrated loads and thermal stresses.
Innovation Solution
A turbine shroud mounting apparatus that includes a load spreader to secure low-ductility shroud segments to a stationary structure, distributing loads and accommodating thermal variations, featuring a laterally-extending plate with a radially protruding boss and fasteners to clamp against the structure, thereby reducing stress and accommodating thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional metallic shroud mounting methods using hangers with complex machined features are used, then metallic shrouds can be securely mounted, but low-ductility materials like CMCs cannot be used and excessive concentrated loads are imposed
Solution Approach 1:
A load spreader component is introduced as an intermediary between the shroud and mounting hardware. This load spreader distributes the mounting loads over a larger area of the shroud material, preventing excessive concentrated loads that would cause failure in low-ductility materials like CMCs, while enabling the use of these advanced materials for high-temperature applications
2Reliability
If metallic mounting hardware with complex machined features is used, then secure mounting is achieved, but low-ductility shroud materials are not amenable to such features and thermal stress issues arise
Solution Approach 1:
The mounting system is segmented into distinct functional components: a simplified mounting hardware element and a load spreader component. This segmentation allows the mounting hardware to provide secure attachment while the load spreader separately handles the function of distributing loads and accommodating thermal expansion, preventing harmful concentrated loads and thermal stresses on the shroud material
3Temperature
If CMC materials are used for shrouds to improve high-temperature capabilities, then temperature resistance is improved, but tensile ductility and strain to failure are reduced
Solution Approach 1:
The mounting approach is changed to accommodate the different mechanical parameters of CMC materials. Instead of using conventional direct mounting that assumes metallic ductility, the load spreader distributes stresses to below the threshold that would cause failure in low-ductility CMC materials, enabling their use in high-temperature environments where their thermal resistance properties are advantageous
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 apparatus securely mounts low-ductility shroud segments while minimizing stress and accommodating thermal variations, ensuring reliable operation in high-temperature environments without imposing excessive loads or thermal stresses.
Implementation Method 1
a load spreader which secures a low-ductility turbine shroud segment to a stationary supporting structure
Implementation Method 2
A fastener engages the boss and the stationary structure, so as to clamp the boss against the stationary structure in a radial direction
Data Source
AI summary
A turbine shroud apparatus for a gas turbine engine having a central axis includes: an arcuate shroud segment comprising low-ductility material and having a cross-sectional shape defined by opposed forward and aft walls, and opposed inner and outer walls, the walls extending between opposed first and second end faces and collectively defining a shroud cavity; an annular stationary structure surrounding the shroud segment; and a load spreader received in the shroud cavity of the shroud segment and mechanically coupled to the stationary structure. The load spreader includes: a laterally-extending plate with opposed inner and outer faces; and a boss which protrudes radially from the outer face and extends through a mounting hole in the outer wall of one of the shroud segments. A fastener engages the boss and the stationary structure, so as to clamp the boss against the stationary structure in a radial direction.