CMC Turbine Nozzle Positioning With Axial Stops and Load Absorption
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Solution Overview
Problem
The integration of ceramic matrix composite (CMC) materials in turbomachine turbine distributors is challenging due to their sensitivity to mechanical stresses, differential thermal expansion, and difficulty in maintaining deterministic positioning and sealing, especially under high-pressure and high-temperature conditions, leading to unpredictable aerodynamic forces and potential overheating.
Innovation Solution
A turbomachine turbine design featuring a CMC distributor with a metal support structure that includes axial stops and masts to ensure deterministic positioning and sealing, allowing blades to deform independently while maintaining consistent passage areas, and incorporating a hollow mast for air pressurization to prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for turbine distributors to withstand high temperatures, then temperature resistance is improved, but sensitivity to mechanical stresses and difficulty in maintaining deterministic positioning worsens
Solution Approach 1:
The distributor is divided into multiple detachable sectors that can be assembled in different configurations. Each sector is independently positionable on the support ring, allowing for deterministic positioning through precise assembly procedures while maintaining the high-temperature resistance of CMC materials throughout the structure.
2Loss of energy
If CMC distributor sectors are used to reduce cooling air requirements, then energy efficiency is improved, but sealing reliability and leakage prevention worsen
Solution Approach 1:
A metal support ring serves as an intermediary component between the CMC distributor sectors and the turbine housing. This metal intermediary provides a rigid, thermally stable foundation that ensures deterministic positioning and reliable sealing surfaces, compensating for the limitations of CMC materials while maintaining the energy efficiency benefits of reduced cooling air requirements.
3Productivity
If CMC materials are used to withstand high operating temperatures, then performance is improved, but differential thermal expansion with metal components worsens
Solution Approach 1:
Different materials are used in different locations within the distributor assembly. CMC materials are used for the distributor sectors where high-temperature resistance is critical, while metal materials are used for the support ring and sealing surfaces where thermal stability and dimensional compatibility are critical. This local differentiation allows each material to perform optimally in its specific location, resolving the thermal expansion incompatibility while maintaining high overall performance.
4Strength
If distributor sectors are allowed to deform independently under stress, then stress distribution is improved, but positioning precision worsens
Solution Approach 1:
The distributor sectors are pre-positioned and secured to the metal support ring during assembly before operation. This preliminary positioning action establishes deterministic locations for each sector, ensuring precise blade-to-blade passage areas. During operation, the sectors can deform independently to distribute stresses, but their positions remain controlled by the rigid metal support ring, thus maintaining both stress distribution benefits and positioning precision.
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 design ensures repeatable blade-to-blade passage areas, reduces leakage, and maintains structural integrity under varying thermal and mechanical stresses, enhancing performance and reducing overheating risks.
Implementation Method 1
an axial stop extending radially from the radially external surface of the outer platform, and the outer metal shell comprises a radially internal surface facing the outer platform and a complementary axial stop extending radially from the radially internal surface of the outer metal shell, the axial stop bearing in the axial direction against the complementary axial stop
Implementation Method 2
incorporating a hollow mast for air pressurization to prevent leakage
Implementation Method 3
allowing the sectors to deform independently of the interfacing metal parts
Implementation Method 4
maintains structural integrity under varying thermal and mechanical stresses
Implementation Method 5
the surface of the axial stop in contact with the complementary axial stop having a machining angle with respect to a plane orthogonal to the axial direction, the machining angle being selected to adjust the orientation of said at least one sector blade relative to the axial direction
Data Source
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AI summary
Disclosed is a turbine comprising a casing and a turbine nozzle having an outer metal shroud (9) that is secured the casing, an inner metal shroud, and a plurality of nozzle sectors (20) that are made of CMC and form a ring extending between the outer shroud (9) and the inner shroud, each sector comprising a strut (6), an inner platform, an outer platform and at least one blade having a hollow profile penetrated by the strut (6). For each blade (20), the outer platform (26) has an axial stop (260) protruding radially outward from the outer platform (26), and the outer metal shroud (9) has a complementary axial stop (96) protruding radially inward from the outer metal shroud (9), the axial stop (260) being upstream and axially supported by the complementary axial stop (96) and being machined with a machining angle selected to adjust the orientation of the at least one blade in the sector in relation to the axial direction (DA).