Turbine Shroud Segment Expansion Joints for Thermal Strain
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Solution Overview
Problem
Turbine shroud segments made from ceramic matrix composite materials experience significant thermally-induced strain due to differing thermal expansion rates between inner and outer walls, leading to potential component damage in high-temperature gas turbine engines.
Innovation Solution
Incorporating expansion joints between the forward and aft shroud portions allows independent thermal expansion and contraction, reducing thermally-induced strain by defining recesses for the arms of the shroud portions within the joints, enabling axial and radial movement without transmitting excessive strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for shroud segments to improve high-temperature capabilities, then temperature resistance is improved, but thermally-induced strain increases due to low CTE and low tensile ductility
Solution Approach 1:
The shroud segment is divided into multiple walls (first wall, second wall, third wall, fourth wall) that can expand and contract independently. This segmentation allows each wall to accommodate thermal expansion separately, reducing overall thermally-induced strain while maintaining the high-temperature capability of CMC materials.
Solution Approach 2:
The invention changes the structural parameters of the shroud segment by introducing expansion joints between walls. These joints modify the thermal expansion behavior by allowing relative movement between walls, thereby reducing strain accumulation while preserving the temperature resistance of the CMC material.
2Strength
If the shroud segment is designed as a complete rectangular box structure, then structural strength is improved, but thermally-induced strain increases due to constrained thermal expansion
Solution Approach 1:
The complete rectangular box structure is segmented into multiple independent walls connected by expansion joints. This segmentation maintains the overall structural strength of the box design while allowing each wall to expand and contract independently, reducing thermally-induced strain and improving component life.
Solution Approach 2:
The expansion joints introduce dynamic capability to the otherwise rigid box structure. The joints allow the walls to move relative to each other during thermal cycling, transforming the static constrained structure into a dynamic adaptive structure that can accommodate thermal expansion without excessive strain.
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 use of expansion joints significantly decreases thermally-induced strain, thereby enhancing the component life of the shroud segment assembly even under extreme thermal gradient conditions.
Implementation Method 1
the inner and outer walls thermally expand and contract at differing rates
Data Source
AI summary
A shroud segment assembly for use within a turbine shroud of a gas turbine engine may generally include a forward shroud portion having a forward outer arm and a forward inner arm extending from a forward wall and an aft shroud portion having an aft outer arm and an aft inner arm extending from an aft wall. Additionally, the shroud segment assembly may include a first expansion joint positioned between the forward and aft shroud portions such that the first expansion joint extends circumferentially between the forward outer arm of the forward shroud portion and the aft outer arm of the aft shroud portion and a second expansion joint positioned between the forward and aft shroud portions such that the second expansion joint extends circumferentially between the forward inner arm of the forward shroud portion and the aft outer arm of the aft shroud portion.