CMC Turbine Ring Elastic Retention for Thermal Expansion
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Solution Overview
Problem
The challenge in aeronautical gas turbine engines is maintaining the position of ceramic matrix composite (CMC) turbine ring sectors while managing thermal expansion differences between CMCs and metal support structures, which affects cooling efficiency and engine performance due to deformation and stress issues.
Innovation Solution
A turbine ring assembly design featuring ring sectors with annular grooves and elastic retaining elements, where the annular projection of the flange expands to maintain sector position at high temperatures without causing stress, utilizing C-clip type elastic attachment portions for secure cold mounting and uniform force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If elastic retaining elements are used to hold CMC ring sectors cold, then assembly is simplified without prestressing, but the retaining elements must be made of material with higher thermal expansion coefficient to maintain holding force at high temperatures
Solution Approach 1:
The patent changes the thermal expansion parameter by selecting retaining element material with a higher thermal expansion coefficient than the CMC ring sectors. This ensures that at high temperatures, the retaining elements expand more to maintain holding force, while at cold temperatures, they provide minimal constraint during assembly.
2Temperature
If CMC ring sectors are used instead of metal, then cooling requirements are reduced and temperature limits are increased, but differential expansion between CMC sectors and metal support structure causes positioning problems
Solution Approach 1:
The patent utilizes thermal expansion by designing the retaining elements and annular projection to expand at different rates with temperature changes. The metal components (retaining elements and projection) have higher thermal expansion coefficients than the CMC ring sectors, allowing them to automatically adjust their dimensions to maintain proper positioning and holding force across the temperature range from cold assembly to hot operation.
3Stress or pressure
If annular projection is housed in annular groove with cold play, then thermal expansion is accommodated without stress on ring sectors, but the projection must be precisely positioned to ensure proper expansion behavior
Solution Approach 1:
The patent applies preliminary anti-action by designing the annular projection and groove interface with intentional cold play (clearance). This preliminary design feature prevents the harmful action of thermal stress on the CMC ring sectors by accommodating the expansion of the metal projection as temperature increases, while the precise positioning ensures the expansion behavior remains controlled and effective.
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 design ensures secure cold assembly with minimal constraints, maintains uniform contact, and allows for effective thermal expansion management, reducing ventilation needs and stress on CMC sectors, thereby enhancing engine performance and temperature limits.
Implementation Method 1
at least the second leg of each ring sector is connected to the ring support structure by at least one elastic retaining element
Implementation Method 2
the annular projection of the first flange being housed in the annular groove of the first lug of each ring sector, a play being present when cold between the annular projection and the annular groove
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A turbine ring assembly comprises a plurality of ring sectors (10) made of a ceramic matrix composite material, forming a turbine ring (1), and a ring support structure (3) having first and second annular flanges (32, 36), each ring sector having tabs (14, 16). The first tab (14) of each ring sector (10) has an annular groove (140) which receives an annular projection (34) of the first flange (32), a clearance (J1) being present in a cold state between the annular projection (34) and the annular groove (140). The second tab (16) of each ring sector (10) is connected to the ring support structure (3) via an elastic retaining element (50).The second tab (16) of each ring sector (10) comprises at least one opening (17) which receives a portion of a retaining element (40) rigidly connected with the second annular flange (36) of the ring support structure (3), a clearance (J2) being present in a cold state between the opening (17) of the second tab (16) and the portion of the retaining element (40) present in said opening, said retaining element being composed of a material with a greater coefficient of thermal expansion than the coefficient of thermal expansion of the ceramic matrix composite material forming the ring sectors.