Auxetic Structures with Angled Slots for Gas Turbine Cooling
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Solution Overview
Problem
The fabrication of auxetic materials with negative Poisson's Ratio (NPR) behavior is hindered by the complexity of embedding intricate geometries within a host matrix, limiting their practical application, particularly in high-temperature environments like gas turbines where efficient cooling and stress reduction are crucial.
Innovation Solution
The development of auxetic structures with obliquely angled elongated apertures or slots that traverse the material thickness at an angle, providing enhanced cooling performance, stress reduction, and negative Poisson's Ratio behavior, while maintaining low porosity and thermal functionalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling holes are used in combustor liners, then cooling function is provided, but stress concentration occurs around the cooling holes leading to reduced fatigue life
Solution Approach 1:
The patent employs asymmetric slot geometries with specific aspect ratios and orientations that are not symmetric about the hole center. This asymmetry creates auxetic behavior where transverse contraction during stretching reduces stress concentration at the cooling feature boundaries, thereby improving fatigue life while maintaining cooling effectiveness
Solution Approach 2:
The patent systematically varies geometric parameters including aspect ratio (length-to-width ratio of slots), orientation angles, and spacing to optimize both cooling performance and stress distribution. By adjusting these parameters, the structure achieves negative Poisson's ratio behavior that simultaneously improves cooling and reduces stress concentration
2Reliability
If auxetic structures with intricate geometries are fabricated, then negative Poisson's Ratio behavior is achieved, but manufacturing complexity increases significantly
Solution Approach 1:
The patent divides the combustor liner into a periodic array of unit cells, each containing simplified slot geometries. This segmentation allows complex auxetic behavior to emerge from simple repeating patterns, making manufacturing feasible through standardized processes while achieving the desired NPR effect at the macro scale
Solution Approach 2:
The patent utilizes a porous structure with cooling slots that can be fabricated using established porous material manufacturing techniques. The slot patterns are designed to achieve NPR behavior through the arrangement and geometry of voids rather than through complex solid structures, simplifying the manufacturing process
3Temperature
If porosity is increased to improve cooling performance, then cooling effectiveness increases, but structural strength decreases
Solution Approach 1:
The patent optimizes the aspect ratio and orientation of cooling slots to achieve maximum cooling effectiveness at minimal porosity levels. By carefully controlling slot dimensions and spacing, the design extracts maximum cooling performance from the available porosity while maintaining structural integrity
4Adaptability or versatility
If conventional positive Poisson's Ratio materials are used, then material availability is high, but stress concentration occurs under compressive loading
Solution Approach 1:
The patent introduces asymmetric slot geometries within conventional materials that induce auxetic behavior. This asymmetry causes the material to contract laterally when stretched, creating a negative Poisson's ratio effect that reduces stress concentration under compressive thermal and mechanical loads while using readily available materials
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
These structures achieve improved cooling effectiveness and stress reduction, increasing the fatigue life of gas turbine components by up to several orders of magnitude, while maintaining or reducing material costs and porosity.
Implementation Method 1
auxetic structures with obliquely angled elongated apertures or slots that traverse the material thickness at an angle, providing enhanced cooling performance, stress reduction, and negative Poisson's Ratio behavior
Implementation Method 2
providing enhanced cooling performance
Data Source
Figure 1~2C
Figure 3A~4D
Figure 5A~6D
AI summary
Auxetic structures, effusion-cooling auxetic sheets, systems and devices with auxetic structures, and methods of using and methods of making auxetic structures are disclosed. An auxetic structure is disclosed which includes an elastically rigid body with opposing top and bottom surfaces. First and second pluralities of elongated apertures extend through the elastically rigid body from the top surface to the bottom surface. The first plurality of elongated apertures extends transversely with respect to the second plurality of elongated apertures. The first and/or second pluralities of elongated apertures are obliquely angled with the top surface of the elastically rigid body. The elongated apertures are cooperatively configured to provide a desired cooling performance while exhibiting stress reduction through negative Poisson's Ratio (NPR) behavior under macroscopic planar loading conditions. For example, the auxetic structure may exhibit an effusion cooling effectiveness of approximately 30-50 Eta and a Poisson's Ratio of approximately -0.2 to -0.9%.