Wedge-Shaped Ceramic Blade Track Segments for Gas Turbine Shroud Sealing
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Solution Overview
Problem
Current blade track designs in gas turbine engines face challenges in minimizing gas leakage and withstanding high temperatures due to uneven stress distribution and material limitations, particularly in ceramic materials that are weak in tension but strong in compression.
Innovation Solution
A blade track assembly comprising wedge-shaped isotropic ceramic blade track segments and an anisotropic ceramic-matrix composite annular band, with a ceramic cloth ring for sealing, that maintains the segments in a ring form through radial inward force, minimizing stress concentrations and enhancing thermal expansion compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic materials are used for blade track segments to withstand high temperatures, then temperature resistance is improved, but tensile strength becomes insufficient due to ceramic weakness in tension
Solution Approach 1:
The patent changes the stress state parameter from including tensile stress to purely compressive stress by using pre-compression forces and wedge-shaped segments. This allows ceramic materials to function effectively despite their tensile weakness, as the design ensures stresses remain compressive throughout operation.
Solution Approach 2:
The patent employs composite construction by combining multiple ceramic segments with compressive pre-loading mechanisms, creating a system where the overall structure compensates for the material's tensile weakness through maintained compressive states and geometric configuration.
2Reliability
If blade track segments are designed to minimize gas leakage, then sealing performance is improved, but stress distribution becomes uneven leading to structural weaknesses
Solution Approach 1:
The blade track is divided into multiple wedge-shaped ceramic segments arranged in a ring. This segmentation allows for controlled stress distribution where each segment experiences primarily compressive forces, and the collective arrangement maintains uniform overall stress while achieving effective sealing between segments.
Solution Approach 2:
Instead of trying to make the material resistant to tensile stresses from sealing forces, the design inverts the approach by pre-compressing the segments so that sealing forces add to the compressive state rather than creating tension. This reverses the typical stress management strategy to better suit ceramic material properties.
3Stability of the object's composition
If annular bands apply radially inward force to maintain ring form, then structural stability is improved, but tensile stresses increase which ceramic materials cannot withstand
Solution Approach 1:
The patent changes the stress parameter regime by ensuring the annular band and pre-compression mechanisms maintain compressive stresses in the ceramic segments. The design parameters are selected so that radial inward forces translate to compressive loading on segments rather than tensile stresses, matching ceramic material strengths.
Solution Approach 2:
The patent converts the potentially harmful tensile stresses that would normally result from radially inward band forces into beneficial compressive stresses. Through the wedge-shaped segment geometry and pre-compression setup, the band's contracting force becomes a source of stabilizing compression rather than damaging tension.
4Stress or pressure
If wedge-shaped segments are used to distribute compressive loads uniformly, then load distribution is improved, but manufacturing complexity increases
Solution Approach 1:
The blade track is segmented into standardized wedge-shaped units with consistent geometric parameters. This segmentation enables uniform load distribution across the ring while allowing each segment to be manufactured independently using standardized processes, thereby managing complexity through modularity and repetition.
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 reduces gas leakage, maintains structural integrity under high temperatures, and improves fuel efficiency by ensuring compressive loads are applied uniformly, thus enhancing the performance and durability of ceramic blade tracks.
Implementation Method 1
The annular band includes anisotropic ceramic-matrix composite materials. Each of the plurality of blade track segments are wedge shaped and the plurality of blade track segments are positioned circumferentially around an axis to form a ring. The annular band is disposed circumferentially around each of the plurality of blade track segments to provide a radially inward force that acts against each of the plurality of blade track segments such that each of the plurality of blade track segments act as a voussoir to maintain a form of the ring.
Data Source
AI summary
A blade track assembly for a gas turbine engine includes a plurality of blade track segments. The blade track segments are arranged circumferentially around a central axis to form a blade track. Each of the plurality of blade track segments includes a first circumferential end face, a second circumferential end face opposite the first circumferential end face, a radially-outer surface, and a radially inner surface opposite the radially-outer surface.