Porous Ceramic Floatwall Panels for Transpiration Cooling
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Solution Overview
Problem
Conventional cooling techniques for gas turbine engine combustion sections are inefficient and can lead to material damage due to 'hot spots' and oxidation, resulting in cracks and material loss.
Innovation Solution
The use of floatwall panels made from porous ceramic material with a porosity gradient along their length, width, and depth, which are attached to the combustion section using mounts to maintain a spaced relationship, allowing for more efficient transpiration cooling by varying porosity to address temperature-dependent hot spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If film-cooling holes are drilled through materials at relatively shallow angles, then cooling air can be provided to cool the surface, but the technique is relatively inefficient in the use of cooling air and can still result in hot spots that produce cracks and material loss
Solution Approach 1:
The patent applies porous ceramic materials with controlled porosity gradients to enable transpiration cooling. The porous structure allows cooling air to permeate through the material in a controlled manner, with higher porosity regions directing more cooling flow to hot spots. This resolves the contradiction by providing efficient cooling through the material bulk rather than relying on shallow surface holes, thereby improving cooling air efficiency while maintaining surface temperature control.
Solution Approach 2:
The patent implements spatially varying porosity within the ceramic material, with higher porosity in regions corresponding to hot spots and lower porosity in cooler regions. This local variation in material property directs cooling airflow precisely where needed, improving cooling efficiency at hot spots without wasting cooling air in already-cooled areas, thus resolving the efficiency contradiction.
2Reliability
If film-cooling holes are drilled through materials, then cooling air can reach the surface, but hot spots still occur that produce cracks and material loss due to oxidation
Solution Approach 1:
The porous ceramic material with optimized porosity gradient provides uniform cooling across the surface, particularly at hot spot locations. The controlled pore structure enables consistent transpiration cooling that prevents temperature extremes, thereby eliminating the conditions that lead to thermal cracking and oxidation, thus improving material integrity while eliminating harmful hot spots.
Solution Approach 2:
The patent changes the physical parameter of porosity spatially within the material, creating a gradient that adapts to the thermal environment. By varying porosity from region to region, the material optimizes cooling performance locally, preventing hot spots that would otherwise cause cracks and oxidation, thereby improving reliability.
3Loss of energy
If porous ceramic material with porosity gradient is used, then cooling airflow efficiency is enhanced and cooling air requirement is reduced, but the material structure becomes more complex
Solution Approach 1:
The porous ceramic material with porosity gradient achieves superior cooling efficiency that reduces the total amount of cooling air needed. Although the internal structure is more complex than solid material, the single-piece porous structure integrates both structural and cooling functions, avoiding the need for separate cooling systems. This resolves the contradiction by reducing overall system complexity despite the sophisticated internal porosity distribution.
Solution Approach 2:
The porous ceramic material represents a composite structure with controlled void spaces distributed throughout the solid matrix. The porosity gradient creates a functionally graded material that optimizes both mechanical strength and cooling performance. This composite approach allows the material to achieve efficient cooling with less air while maintaining structural integrity, resolving the apparent complexity contradiction.
4Temperature
If porosity is increased in high-temperature areas, then transpiration cooling efficiency is improved, but material strength may be reduced
Solution Approach 1:
The porosity gradient creates local quality variations where high porosity (for cooling) is concentrated at hot spot locations on the surface, while the interior and cooler regions maintain lower porosity for structural strength. This spatial differentiation resolves the contradiction by providing high cooling efficiency only where thermal loads are highest, while preserving material strength in regions where it is most critical.
Solution Approach 2:
The porosity parameter is varied spatially through the material thickness and across the surface, creating a gradient that optimizes the trade-off between cooling efficiency and mechanical strength. By controlling porosity as a continuous variable rather than a uniform property, the material achieves both high cooling performance at hot spots and adequate structural integrity in less demanding regions.
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
This solution enhances cooling airflow efficiency, reduces the requirement for cooling air, and mitigates material damage by strategically increasing porosity in high-temperature areas, preventing blockages in gas flow paths while maintaining structural integrity.
Implementation Method 1
The use of floatwall panels made from porous ceramic material with a porosity gradient along their length, width, and depth, which are attached to the combustion section using mounts to maintain a spaced relationship, allowing for more efficient transpiration cooling by varying porosity to address temperature-dependent hot spots.
Implementation Method 2
Cooling air is provided to a backside of these materials, thereby allowing the air to travel through the film-cooling holes and cool a surface of the material that is closest to the combusting fuel and air mixture.
Implementation Method 3
Cooling of materials that are used to form combustion sections of gas turbine engines is accomplished using various techniques.
Implementation Method 4
Cooling air is provided to a backside of these materials, thereby allowing the air to travel through the film-cooling holes and cool a surface of the material
Data Source
AI summary
Floatwall panel assemblies and related systems are provided. A floatwall panel assembly includes a panel formed of porous ceramic material, the porous ceramic material exhibiting a porosity gradient along at least one of a length, a width and a depth of the panel, the panel lacking a substrate, formed of a material other than porous ceramic material, for supporting the porous ceramic material.