CMC Turbine Ring Assembly Thermal Expansion Compensation
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Solution Overview
Problem
Ceramic matrix composite (CMC) turbine ring sectors face challenges in maintaining position and controlling shape due to differential expansions between metal support structures and CMC materials, leading to vibration and performance issues in gas turbine engines.
Innovation Solution
A turbine ring assembly design featuring ring sectors made of CMC with annular flanges and holder elements of higher thermal expansion materials, which provide radial clearance and thrust portions to secure the sectors without assembly clearance, and adjustable eccentric clamping elements to compensate for thermal expansions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If CMC ring sectors are used to reduce cooling requirements, then cooling efficiency is improved, but positioning stability deteriorates due to differential expansion with metal support structure
Solution Approach 1:
The invention changes the material parameter (coefficient of thermal expansion) of the holder elements to be higher than that of CMC ring sectors. This parameter change allows the holder elements to expand more than the ring sectors during heating, maintaining compressive contact and stable positioning without requiring clearance, thus resolving the positioning stability issue while preserving the cooling efficiency benefits of CMC materials
Solution Approach 2:
The invention uses a composite approach by combining CMC ring sectors with metal holder elements that have different thermal expansion characteristics. This composite structure leverages the low thermal expansion of CMC for dimensional stability and the high thermal expansion of metal holder elements for adaptive clamping, solving the positioning problem while maintaining the energy efficiency advantages of CMC
2Stability of the object's composition
If clearance is provided between holder elements and openings, then positioning stability is improved, but manufacturing precision deteriorates due to loss of shape control
Solution Approach 1:
The invention eliminates clearance by changing the thermal expansion parameter relationship between holder elements and ring sectors. The holder elements are made of material with higher thermal expansion coefficient, ensuring they remain in compressive contact with the ring sectors during thermal cycles, providing both positioning stability and precise shape control without clearance
Solution Approach 2:
The invention applies preliminary compressive action through the holder elements that expand during heating to maintain continuous contact with the CMC ring sectors. This preliminary anti-action prevents any potential movement or vibration that would occur with clearance, ensuring both positioning stability and manufacturing precision are maintained
3Stability of the object's composition
If holder elements are made of material with higher thermal expansion, then positioning stability is improved through compensating expansion, but device complexity increases
Solution Approach 1:
The invention simplifies the overall device by making a straightforward parameter change: selecting holder element material with higher thermal expansion coefficient than CMC ring sectors. This single parameter change enables automatic compensation for differential expansion through the natural thermal behavior of materials, avoiding complex adjustment mechanisms while maintaining positioning stability
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 effectively holds CMC ring sectors without assembly clearance, maintains shape and performance, and compensates for thermal expansion-induced losses, reducing vibration and improving engine efficiency.
Implementation Method 1
The holder elements are made of a material having a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors
Data Source
AI summary
A turbine ring assembly includes ring sectors made of ceramic matrix composite material forming a turbine ring and a ring support structure having first and second annular flanges, each ring sector having first and second tabs held between the flanges. First and second holder elements secured to the first annular flange being received in first and second openings in the first tab, while first and second holder elements secured to the second annular flange are in first and second openings in the second tab. Radial clearance is being present when cold between the openings and the portions of the holder elements present in the openings. The first and second annular flanges include, on their faces facing the first and second tabs, a plurality of thrust portions distributed in circumferential manner over the flanges, the ends of the tabs, when cold, being in radial abutment against two thrust portions.