CMC Flange Cooling Cavity for Thermal Stress Reduction
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Solution Overview
Problem
CMC components with flanges, such as blade outer air seals, face challenges in cooling due to increased material thickness under flanges, leading to higher thermal gradients and thermal stresses, which existing manufacturing methods fail to adequately address.
Innovation Solution
Introduce a cooling cavity beneath flanges, such as T-shaped flanges, within CMC components during the layup process, utilizing a Y-weave of ceramic fiber piles to form a triangular cross-section cooling channel, with inlet and outlet passages for cooling fluid, and utilize tooling or fugitive materials to maintain cavity shape during densification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If CMC components are made with flange structures (e.g., T-shaped flanges) to provide load bearing features, then structural strength is improved, but material thickness increases leading to higher thermal gradients and thermal stresses
Solution Approach 1:
The flange structure is segmented into multiple functional zones: a cooling cavity is created within the flange thickness, dividing the thermal path into surface cooling region and internal cooling region. This segmentation allows the flange to maintain structural strength while creating dedicated cooling pathways that reduce thermal gradients through the increased thickness.
Solution Approach 2:
The cooling cavity is positioned specifically in the high-thickness region of the flange where thermal gradients are most severe. By localizing the cooling structure to this critical area, the patent addresses the thermal stress problem at the exact location where it occurs, while maintaining the overall structural integrity of the flange.
2Strength
If CMC components are made with flange structures to provide load bearing features, then structural strength is improved, but thermal stresses increase due to higher material thickness
Solution Approach 1:
The flange is segmented to create a cooling cavity that divides the thermal stress distribution. The cavity creates separate thermal pathways, reducing the continuous thermal stress buildup that would occur in solid thick material. This segmentation approach maintains structural strength while mitigating thermal stress concentration.
Solution Approach 2:
The cooling cavity acts as an intermediary structure within the flange that mediates between the hot gas path exposure and the internal cooling requirements. It provides a dedicated pathway for cooling fluid to reach the high-thickness region, reducing thermal stresses without compromising the load-bearing function of the flange.
3Temperature
If cooling fluid passages are added to cool CMC components, then thermal management is improved, but device complexity increases
Solution Approach 1:
The cooling passages are merged with the flange structure itself rather than being separate external components. The cooling cavity is formed within the flange material, and inlet/outlet passages are integrated into the flange geometry. This merging approach provides effective cooling while minimizing additional structural complexity.
Solution Approach 2:
The cooling cavity and passages are formed during the initial layup and densification process, before the component is assembled into the final engine. By creating the cooling structure preliminarily during manufacturing, the patent avoids adding complexity during assembly or operation.
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 cooling cavity effectively reduces thermal gradients and thermal stresses in high-thickness regions, enhancing the operational lifespan and efficiency of CMC components by providing efficient internal cooling.
Implementation Method 1
The region beneath such flanges has an increased material thickness in comparison to other portions of the component. These greater thicknesses render cooling more difficult and result in the formation of higher thermal gradients which in turn result in higher through-thickness and in-plane thermal stresses.
Implementation Method 2
precautions can be taken to cool CMC components by exposing the components to a flow of cooling fluid (e.g., air)
Data Source
AI summary
A method is described for introducing cooling cavities into CMC components beneath flanges such as T-shaped flanges within the CMC components. During layup, preform is made having flanges formed from a Y-shaped weave in which plies of woven ceramic fiber tows form a radial flange section extending from a base of the preform and two bifurcated arms. The plies of the two bifurcated arms and plies of the base form a cooling cavity having a triangular cross section beneath the flange. Cooling fluid inlet passages are provided to permit cooling fluid to enter the cooling cavity and thereby cool the internal region of the CMC component to reduce formation of thermal stresses.