CMC Heat Shield Retention for Gas Turbine Combustors
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Solution Overview
Problem
Metal fasteners used to secure ceramic matrix composite (CMC) heat shields in gas turbine engines lose strength at high temperatures, undermining the desired high-temperature capability of CMCs and leading to potential binding stresses due to different thermal expansion rates.
Innovation Solution
A combustor design featuring a ceramic matrix composite heat shield with offset mount flanges and attachment posts that allow for relative movement between the heat shield and the combustor shell, preventing binding stresses through strategically sized and shaped attachment apertures and retainers that engage the posts, ensuring secure attachment without compromising thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal fasteners are used to secure CMC heat shields, then the heat shield can be attached to the combustor shell, but the fasteners lose strength and may melt at CMC operating temperatures
Solution Approach 1:
The patent removes metal fasteners from the high-temperature zone by using a retention system that engages with the CMC heat shield at lower temperature regions. The retention system includes a retention member that interfaces with the heat shield without requiring metal fasteners to withstand extreme temperatures, thereby extracting the fastening function from the high-temperature environment where it fails.
Solution Approach 2:
The patent introduces a retention system as an intermediary between the CMC heat shield and the combustor shell. This retention system acts as a mediator that connects the two components without requiring direct metal-to-CMC fastening at high temperatures. The retention system includes retention members that engage with the heat shield and are retained by the combustor shell, providing a buffer zone that protects the CMC from thermal stress while maintaining secure attachment.
2Reliability
If the heat shield is rigidly attached to the combustor shell, then secure attachment is achieved, but binding stresses occur due to different thermal expansion rates
Solution Approach 1:
The patent implements a dynamic retention system that allows for differential thermal expansion between the CMC heat shield and the combustor shell. The retention system includes retention members with engagement features that can accommodate movement and expansion, transforming the rigid attachment into a flexible connection. This dynamic design permits the heat shield to expand and contract independently while remaining securely attached, thereby eliminating binding stresses caused by thermal expansion mismatches.
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 maintains the high-temperature capability of CMC heat shields while managing thermal stresses, ensuring the combustor shell remains protected from intense combustion temperatures without compromising the integrity of the heat shield.
Implementation Method 1
The heat shield is coupled to the dome panel and arranged within the internal cavity to shield the dome panel from temperatures developed by burning fuel
Implementation Method 2
The attachment aperture may be sized and shaped so that the dome panel moves relative to the heat shield due to different rates of thermal expansion
Data Source
AI summary
A combustor adapted for use in a gas turbine engine a combustor shell, a heat shield, and a heat shield retainer. The combustor shell is made from metallic materials and is formed to define an internal cavity. The heat shield is formed from ceramic matrix composite materials and is coupled to the dome panel. The heat shield retainer is configured to retain the heat shield to the combustor shell.