Load-Bearing CMC Nozzle Diaphragm for Turbine Force Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ceramic matrix composite (CMC) turbine distributor stages face challenges in deterministic securing with internal shells, particularly in maintaining axial stability and absorbing aerodynamic forces, while also dealing with significant pressure differentials that exceed the permissible loads of CMC materials.
Innovation Solution
The proposed turbomachine turbine incorporates a CMC distributor stage with an outer metal support shroud and an inner metal support shroud, featuring CMC ring sectors that are radially attached to an external metal support shell. This design includes a radial attachment system with a mast that minimizes bending moments and allows the CMC ring sector to deform independently of metal parts, while the metal mast takes up pressure differential forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC ring sectors are directly secured to the inner support shell, then the distributor stage can operate at high temperatures, but the CMC material cannot withstand the pressure differential forces exerted on the casing
Solution Approach 1:
A metallic diaphragm is introduced as an intermediary element between the CMC ring sectors and the inner support shell. The diaphragm absorbs the pressure differential forces through its load-bearing structure (ribs and protrusions), preventing these forces from being transmitted to the CMC material which cannot withstand them, while allowing the CMC distributor stage to operate at high temperatures.
Solution Approach 2:
The solution employs a composite structure combining CMC ring sectors for high-temperature operation with a metallic diaphragm for mechanical strength and pressure force absorption. This hybrid approach leverages the thermal resistance of CMC and the mechanical strength of metal to resolve the contradiction between temperature capability and pressure force resistance.
2Stability of the object's composition
If the CMC ring sector is rigidly fixed to the inner support shell, then axial stability is achieved, but the CMC part cannot deform independently under thermal and pressure effects
Solution Approach 1:
The connection between the CMC ring sector and the inner support shell is made dynamic rather than rigid. The diaphragm with its flexible membrane and load-bearing ribs allows the CMC part to deform axially under thermal and pressure effects while maintaining stability through the diaphragm's structural support and its connection to the inner support shell.
3Force
If a reinforcing mast is used to absorb pressure differential forces, then the forces are taken up, but the deterministic retention of the CMC part is insufficient
Solution Approach 1:
The load-bearing function is segmented from the CMC ring sector and assigned to a separate metallic diaphragm structure. The diaphragm is divided into a flexible membrane portion and load-bearing ribs with protrusions that engage with the inner support shell, creating multiple discrete load transfer paths that provide deterministic retention while absorbing pressure forces.
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
This solution provides deterministic support and positioning of the CMC distributor stage, allowing it to deform under temperature and pressure effects independently of metal parts, while effectively managing aerodynamic and pressure differential forces within permissible limits of the CMC material.
Implementation Method 1
a metallic diaphragm having a load-bearing structure, said load-bearing structure being designed to absorb the pressure differential forces so as to prevent said pressure differential forces from acting on the CMC ring sector in excess of a permissible load
Implementation Method 2
CMC has greater rigidity and lower expansion. It behaves better in compression, but its permissible tensile stresses are lower than those of metal.
Implementation Method 3
allowing the CMC ring sector to deform independently of the metal parts
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Turbine (1) for a turbomachine, comprising a casing (4) and a turbine nozzle diaphragm stage (2), the nozzle diaphragm stage (2) of the turbine (1) comprising an outer metallic ferrule (9) firmly joined to the casing (4), an inner metallic ferrule (5) and a plurality of ring sectors (20) made of a ceramic matrix composite material, forming a ring between the outer metallic ferrule (9) and the inner metallic ferrule (5) and having an inner ferrule and an outer ferrule, each ring sector (20) having an inner platform (24) that forms part of the inner ferrule, an outer platform (26) that forms part of the outer ferrule, and at least one blade (28) extending between the outer platform (26) and the inner platform (24) and firmly joined thereto. Each sector (20) is secured to the outer metallic ferrule by at least one assembly comprising a screw and a nut, the screw extending through the outer platform (26) of the sector (20) and the outer metallic ferrule.