Emissive Composite Materials for Electron Transpiration Cooling
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Solution Overview
Problem
Conventional heat dissipation techniques for high-performance applications like air and space vehicles are inadequate, particularly during hypersonic flight, as they increase vehicle weight, complicate engine design, and struggle with cooling narrow aerodynamic leading edges, where ablative heat shields are not suitable and can saturate under severe thermal loads.
Innovation Solution
Emissive composite materials comprising a refractory metal matrix and ceramic electride materials that emit electrons upon heating, providing a passive cooling mechanism known as electron transpiration cooling, which can exceed the cooling effects of radiative cooling and retain the mechanical properties of the base metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If internal cooling systems such as heat pipes and refrigerant circulators are used, then cooling effectiveness is improved, but vehicle weight increases significantly
Solution Approach 1:
The patent replaces mechanical cooling systems (heat pipes, refrigerant circulators) with a material-based solution. The refractory metal matrix composite material inherently provides thermal management through its composition and structure, eliminating the need for separate mechanical cooling components and thereby reducing vehicle weight while maintaining cooling effectiveness
Solution Approach 2:
The patent employs a refractory metal matrix composite material that combines multiple materials to achieve superior thermal properties. This composite structure enables effective heat dissipation through the material itself, providing passive thermal management without adding the weight of active cooling systems
2Temperature
If ablative heat shields are used for thermal protection, then thermal protection effectiveness is improved, but vehicle weight increases and shape changes occur
Solution Approach 1:
The patent uses a refractory metal matrix composite material that provides thermal protection without the weight penalty of ablative heat shields. The composite structure with ceramic electride particles in the refractory metal matrix enables heat dissipation through electron emission, maintaining protection effectiveness while reducing weight
Solution Approach 2:
The patent replaces the consumable ablative heat shield mechanism with a stable, non-consumable refractory metal matrix composite. This substitution eliminates the weight of thick ablative layers and avoids shape changes, as the material provides passive thermal protection without being consumed during operation
3Temperature
If forced air or compressed gas cooling is used, then heat dissipation is improved, but engine design complexity increases
Solution Approach 1:
The patent replaces forced air or compressed gas cooling systems with a material-based thermal management solution. The refractory metal matrix composite material provides passive heat dissipation through its inherent properties, eliminating the need for complex air flow control systems, valves, and ducts, thereby reducing engine design complexity while maintaining heat dissipation effectiveness
4Temperature
If ablative heat shields are used for narrow aerodynamic leading edges, then thermal protection is attempted, but the narrow geometry makes effective protection difficult
Solution Approach 1:
The patent employs a refractory metal matrix composite material that can be applied as a coating or integrated into narrow aerodynamic leading edge structures. The composite's thermal management properties work effectively in thin-section applications, providing thermal protection adapted to narrow geometries where ablative heat shields would be ineffective
Solution Approach 2:
The patent enables localized thermal management tailored to specific geometric requirements. The refractory metal matrix composite can be applied selectively to narrow aerodynamic leading edges, providing thermal protection adapted to the local geometry rather than requiring thick ablative layers that would be ineffective in narrow sections
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 emissive composite materials offer a passive and efficient heat dissipation method that significantly surpasses conventional cooling techniques, maintaining mechanical stability and allowing for enhanced thermal management in high-temperature environments, particularly suitable for high-tolerance applications where ablative strategies are unsuitable.
Implementation Method 1
a ceramic electride material in the refractory metal matrix; a collector configured to receive electrons emitted across open space by the ceramic electride material upon heating of the part and the emissive composite material
Data Source
AI summary
Electron emission from an emissive substance, such as an emissive composite material, can be employed as a heat dissipation technique and mechanism for a part subject to operational heating. Emissive composite materials containing a refractory metal matrix and a ceramic electride material in the refractory metal matrix can be utilized for this purpose. Emissive composite materials can retain the thermal stability of the base refractory metal and emit electrons upon being heated to a sufficiently high temperature. Cooling systems and associated methods can utilize a collector configured to receive electrons emitted across open space by the ceramic electride material upon heating, and a conductive pathway can allow the electrons to be returned to the emissive composite material. Accordingly, the emissive composite material and the collector define a portion of an electrical circuit.