Turbine Ring Assembly Curved Support Surfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Turbine ring assemblies using ceramic matrix composite (CMC) materials face mechanical stress and embrittlement due to hot expansion of metal attachment parts, leading to uneven stress distribution and potential leakage issues.
Innovation Solution
A turbine ring assembly design featuring curved rectilinear support surfaces with variable thickness, electro-eroded to standardize contact force distribution and reduce stress levels, combined with a ring support structure that includes annular and radial flanges to maintain axial contact and sealing, and utilize pins and lugs for secure positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal attachment parts are used to connect CMC ring sectors, then structural integrity is improved, but hot expansion of metal parts generates mechanical stress and embrittlement of CMC sectors
Solution Approach 1:
The support surfaces are designed with variable thickness, being thicker at the ends and thinner in the middle section, creating non-uniform local properties that adapt to the stress distribution pattern. This local quality variation allows the structure to better accommodate thermal expansion differences between metal and CMC materials while reducing stress concentrations at critical locations.
Solution Approach 2:
The geometry of the support surfaces is modified by changing the thickness parameter along the axial direction. By varying the thickness parameter from constant (straight) to variable (curved with minimum in middle, maximum at ends), the mechanical properties of the support structure are optimized to reduce stress on CMC ring sectors during thermal cycling.
2Ease of manufacture
If straight rectilinear support surfaces are used, then manufacturing is simplified, but uneven stress distribution occurs with stress concentrations at inter-sector locations
Solution Approach 1:
The support surfaces are transformed from straight rectilinear geometry to curved geometry with variable thickness. The curvature is defined by a mathematical function that creates a smooth profile with minimum thickness at the middle and maximum at the ends. This curved geometry redistributes the contact pressure more uniformly across the support surface, eliminating stress concentrations at inter-sector locations while maintaining manufacturability through controlled curvature.
3Reliability
If pre-tightening is applied to maintain axial contact, then sealing is improved, but non-uniform force distribution increases bending stresses in CMC ring
Solution Approach 1:
The variable thickness profile of the support surfaces creates different local stiffness characteristics. The thicker end regions provide stronger support and load distribution, while the thinner middle section allows for controlled deformation. This local quality variation enables the structure to maintain uniform contact pressure under pre-tightening conditions, ensuring sealing while distributing bending stresses more evenly across the CMC ring.
Solution Approach 2:
The curved geometry with variable thickness transforms the rigid straight support into a compliant structure that can adapt to thermal expansion. The curvature allows the support surface to conform to the deformed state of the CMC ring under pre-tightening, maintaining uniform axial contact pressure for sealing while reducing peak bending stresses by distributing the load more evenly across the contact area.
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 achieves a 80% reduction in maximum stress during assembly and 20% reduction during operation compared to straight rectilinear supports, enhancing sealing and reducing mechanical stress concentrations in CMC rings while maintaining deterministic sector positioning.
Implementation Method 1
curved rectilinear support surfaces with variable thickness, electro-eroded to standardize contact force distribution and reduce stress levels
Implementation Method 2
these metal attachment parts undergo hot expansion, which can lead to mechanical stressing of the CMC ring sectors
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A turbine ring assembly comprising ring sectors (10a, 10b) forming a turbine ring (1) and a ring support structure (3), each sector (10a, 10b) having, on a plane of section defined by an axial direction (DA) and a radial direction (DR) of the ring (1), a first and a second attachment lug (14, 16) extending in the radial direction (DR), and said structure (3) comprising a central shell ring (31) from which there extends, as projections, a first and a second radial flange (32, 36) between which the first and second attachment lugs (14, 16) of each sector (10a, 10b) are held. Each sector (10a, 10b) comprises rectilinear seatings (110) mounted on the faces of the first and second attachment lugs (14, 16) respectively in contact with the second annular flange (36) and the annular ring-flange (33) and comprising, along a tangent to the circumferential direction (DC), a thickness that is variable in the axial direction (DA) with a minimum thickness at the first and second ends (102, 104) of the sector (10a, 10b), and a maximum thickness in a middle portion (110m) of the rectilinear seating (110).