Combustor Heat Shield Sealing for Gas Turbine Engines
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Solution Overview
Problem
Gas turbine engines face issues with combustion gas leakage and thermal damage due to coefficient of thermal expansion mismatch between ceramic matrix composite (CMC) heat shields and metallic combustor domes, leading to reduced turbine performance and increased emissions.
Innovation Solution
A combustor assembly with CMC heat shields and seals that extend between adjacent heat shields, featuring a seal design with contact and connecting portions to maintain contact despite thermal expansion, minimizing leakage and impingement on the dome.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC heat shields are used to withstand high combustion gas temperatures, then heat resistance is improved, but gap openings between heat shield segments increase due to CTE mismatch with metallic dome, leading to combustion gas leakage
Solution Approach 1:
A seal member is introduced as an intermediary component between the CMC heat shield and the metallic combustor dome. This seal member compensates for the CTE mismatch by providing a compliant sealing interface that maintains contact and prevents combustion gas leakage despite differential thermal expansion between the heat shield and dome.
Solution Approach 2:
The seal member's material properties and geometric parameters are designed to accommodate thermal expansion differences. The seal can deform or shift position in response to temperature changes, maintaining effective sealing contact between heat shields and the dome across the operating temperature range.
2Object-affected harmful factors
If cooling fluid flow is increased to purge leakage areas, then thermal protection of the dome is improved, but turbine emissions increase and performance decreases
Solution Approach 1:
The seal member converts the potential harmful effect of thermal expansion gaps into a beneficial sealing mechanism. By designing the seal to actively engage with the heat shield edges during thermal expansion, the system transforms what would be leakage pathways into sealed interfaces, eliminating the need for excessive cooling purge flow.
Solution Approach 2:
The seal member is positioned and designed to automatically engage with the heat shield edges through the action of thermal expansion itself. As the combustor dome and heat shields expand with temperature, the seal member is driven into the gaps between heat shield segments, creating a self-actuating sealing mechanism that requires no additional cooling fluid.
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 reduces combustion gas leakage and thermal damage to the combustor dome, enhancing turbine performance and efficiency while minimizing the need for cooling fluid, thus reducing emissions.
Implementation Method 1
the dome fabricated from a metallic material, such that there is a coefficient of thermal expansion (CTE) mismatch or different thermal growth between the components. As the metallic dome expands, the CTE mismatch can drive larger gap openings between CMC heat shield segments
Data Source
AI summary
Combustor assemblies for gas turbine engines are provided. For example, a combustor assembly comprises a combustor dome, a first heat shield having an edge, a second heat shield having an edge, and a seal extending from the edge of the first heat shield to the edge of the second heat shield such that the seal spans a gap between the first heat shield and the second heat shield. In another embodiment, the seal has a first contact portion contacting the edge of the first heat shield, a second contact portion contacting the edge of the second heat shield edge, and a connecting portion connecting the first portion and the second portion. The first contact portion and the second contact portion project away from the connecting portion. Methods for sealing between adjacent heat shields of a combustor assembly also are provided.