Gas Turbine Combustor Mounting for CMC Thermal Expansion
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Solution Overview
Problem
Gas turbine engines face challenges in accommodating the mechanical properties of ceramic matrix composite (CMC) materials, particularly due to mismatched thermal expansion coefficients with traditional metal materials, complicating the attachment and mounting of CMC liners within the engine.
Innovation Solution
A combustor assembly design that incorporates a metal mounting assembly with gaps and bushings to accommodate thermal expansion, allowing for seamless integration of CMC components with metal components, ensuring proper alignment and stability during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC materials are used for liners in the combustion section, then temperature resistance is improved, but attachment complexity increases due to mismatched thermal expansion coefficients
Solution Approach 1:
The mounting assembly is divided into multiple components including a first mounting bracket, second mounting bracket, and support member with distinct functions. The support member includes separate bushings for each liner attachment point, allowing independent accommodation of thermal expansion for each CMC liner while maintaining overall structural integrity
Solution Approach 2:
Bushings are introduced as intermediary elements between the metal mounting assembly and CMC liners. These bushings serve as mediators that accommodate the differential thermal expansion between metal and CMC materials, absorbing expansion forces and preventing direct stress transmission that would cause attachment failure
2Duration of action of stationary object
If CMC materials are used for liners, then high temperature durability is improved, but mounting alignment difficulty increases
Solution Approach 1:
The mounting assembly incorporates dynamic features including gaps between components and flexible bushing elements that can adjust their position and shape. These dynamic elements automatically compensate for dimensional changes in CMC liners during thermal cycling, maintaining proper alignment without requiring precise pre-positioning or complex adjustment mechanisms
Solution Approach 2:
The design explicitly accounts for parameter changes in CMC liner dimensions due to thermal expansion. Gaps are sized and positioned to accommodate expected dimensional changes, and bushings are designed with clearance and flexibility to maintain alignment as the liners expand and contract with temperature variations
3Stability of the object's composition
If gaps are added to the mounting assembly to accommodate thermal expansion, then thermal growth management is improved, but device complexity increases
Solution Approach 1:
Gaps are not added throughout the entire mounting assembly but are strategically placed only at specific locations where thermal expansion occurs. The gaps are positioned between the support member and mounting brackets where dimensional changes are most significant, allowing thermal management without adding complexity to regions where it is not needed
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 solution effectively manages thermal growth and reduces the complexity of mounting CMC components, ensuring reliable operation and durability of the combustor assembly within the gas turbine engine.
Implementation Method 1
CMC materials have different coefficients of thermal expansion than the traditional metal materials. Therefore, the attachment of the inner and outer CMC liners to the metal dome may require a fairly complicated attachment assembly.
Data Source
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AI summary
A combustor assembly (100) for a gas turbine engine includes a combustor dome (112) and a combustion chamber liner (114, 116) attached to or formed integrally with the combustor dome (112). The combustion chamber liner (114, 116) extends between a forward end (118, 122), and an aft end (120, 124), and together with the combustor dome (112) at least partially defines a combustion chamber (108). The combustor assembly (100) additionally includes a mounting assembly (136) attached to the liner proximate the forward end of the liner for supporting the combustor dome (112) and combustion chamber liner (114, 116) within the gas turbine engine relative to a structural component of the gas turbine engine.