CMC Turbine Nozzle Radial Attachment to Metal Casing
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Solution Overview
Problem
Current metal turbine nozzles face damage due to aerodynamic forces and pressure differences, and ceramic matrix composite (CMC) nozzles are difficult to attach to metal casings due to differential expansion and abrasiveness, leading to complex manufacturing and attachment issues.
Innovation Solution
A CMC nozzle with a blade and connecting part produced in one piece, featuring radial fibrous reinforcements and a radial flange for direct fastening to a radial wall, which includes an intermediate metal part for secure attachment, preventing moment creation and friction-related degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CMC nozzle is attached to a metal casing using traditional flange methods, then the nozzle can be secured to the casing, but the differential thermal expansion between CMC and metal materials causes attachment failures and the abrasive CMC material damages the metal casing rails
Solution Approach 1:
The nozzle is segmented into a blade portion and a connecting part produced in one piece. The connecting part extends radially outward and is fastened to a radial wall that is itself fastened to the casing, creating a multi-level attachment system that isolates the CMC material from direct contact with the metal casing rails, thereby preventing abrasion damage while accommodating thermal expansion differences
Solution Approach 2:
A radial wall structure serves as an intermediary element between the CMC connecting part and the metal casing. The connecting part is fastened to the radial wall, which is then fastened to the casing, creating a buffer zone that handles thermal expansion mismatch and prevents direct abrasive contact between CMC and metal surfaces
2Ease of manufacture
If a CMC nozzle with complex shape is manufactured to match metal nozzle geometry, then the nozzle can be attached in the same way as metal nozzles, but the manufacturing complexity increases significantly
Solution Approach 1:
The nozzle design segments the functional requirements: the blade portion maintains the complex aerodynamic shape needed for performance, while the connecting part adopts a simpler radial geometry that extends outward for straightforward fastening to the radial wall, reducing manufacturing complexity while preserving attachment simplicity
Solution Approach 2:
The connecting part extends in the radial dimension outward from the blade, creating a new attachment interface that simplifies the fastening process. This radial extension allows the CMC nozzle to be attached using a different dimensional approach than traditional axial flange connections, reducing geometric complexity
3Ease of manufacture
If the connecting part rests on a casing rail, then the attachment is simple, but the forces from aerodynamic flow and pressure differences create damaging moments at the attachment point
Solution Approach 1:
The attachment system is segmented into multiple fastening points distributed on the radial wall. The connecting part is fastened to the radial wall through multiple attachment locations rather than resting on a single rail, distributing the aerodynamic forces and pressure differential loads to prevent damaging moments while maintaining attachment simplicity
Solution Approach 2:
The radial wall acts as an intermediary structure that provides a robust fastening surface for the connecting part. Instead of direct rail contact, the radial wall mediates the force transmission, distributing aerodynamic and pressure loads across multiple fastening points to eliminate damaging concentrated moments
Data Source
AI summary
The invention relates to an assembly comprising a turbomachine casing (7) and a nozzle made of ceramic matrix composite material having a blade (21), the frontside and backside surfaces of which delimit an internal cavity, and which is connected at its radially external end by a connecting part (31) of the nozzle to the casing (7), said connecting part (31) extending substantially radially outwards, the blade (21) and said connecting part (31) being formed in one piece, said assembly being characterized in that the connecting part (31) is fastened to a first radial wall (51) integral with the casing (7) by fastening means (53).