Brayton Cycle Cooling for High-Speed Vehicle Combustor Walls
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Solution Overview
Problem
Current cooling systems for high-speed vehicles, such as scramjets, are limited in their ability to manage high heat loads at supersonic and hypersonic speeds, leading to fuel coking and performance deterioration, and require overfueling which increases weight and reduces efficiency.
Innovation Solution
A closed Brayton cycle cooling system using a second fluid that circulates through the combustor wall to absorb heat, allowing for efficient heat transfer to the fuel and reducing the need for overfueling, while maintaining high combustor wall temperatures below the coking limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fuel is used as the primary coolant to prevent coking, then combustor wall temperature is restricted to moderate values, but this leads to overfueling and performance deterioration
Solution Approach 1:
A heat exchanger is introduced as an intermediary component between the fuel and combustor wall. The heat exchanger allows thermal energy to be transferred from the fuel to the combustor wall without direct thermal contact, enabling the fuel to be cooled to prevention coking temperatures while the combustor wall receives sufficient thermal energy for efficient combustion. This mediator resolves the contradiction by decoupling the thermal coupling between fuel and combustor wall.
2Reliability
If excess fuel is used for cooling, then fuel overheating and coking are prevented, but this leads to overfueling and added weight
Solution Approach 1:
The heat exchanger serves as an intermediary that enables efficient heat transfer from the fuel to the combustor wall. This allows the system to use the minimum necessary fuel for cooling purposes, as the heat exchanger efficiently extracts the required thermal energy. The mediator improves the effectiveness of fuel cooling while minimizing the amount of excess fuel needed, thereby reducing the weight penalty associated with overfueling.
3Device complexity
If fuel temperature is directly coupled to combustor wall temperature, then cooling is simple, but this limits the maximum temperature capability to preclude coking
Solution Approach 1:
The heat exchanger acts as an intermediary thermal coupling device between the fuel and combustor wall. While it adds a component to the cooling system, it enables independent temperature control of the fuel and combustor wall. The fuel can be maintained at lower temperatures to prevent coking, while the combustor wall can operate at higher temperatures for improved performance. This mediator achieves the goal of preventing coking while enabling higher maximum operating temperatures.
4Speed
If chemical heat sink systems are used to extend cooling capability, then Mach number capability increases, but this leads to short catalyst life and catalyst poisoning
Solution Approach 1:
The heat exchanger serves as a physical intermediary that enables efficient heat transfer without requiring chemical reactions or catalysts. By using direct thermal conduction through the heat exchanger walls, the system achieves effective fuel cooling and heat recovery without the need for chemical heat sink materials. This eliminates the reliability issues associated with catalyst degradation and poisoning, while still enabling high Mach number operation through efficient thermal management.
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 extends the Mach number capability beyond Mach 8, reduces fuel flow rates, and provides weight savings by decoupling combustor wall temperature from fuel temperature, enabling efficient high-speed operation without fuel coking and overfueling.
Implementation Method 1
The second fluid may be circulated within the combustor wall and heat may be transferred from the combustor wall to the second fluid, thus cooling the combustor wall
Implementation Method 2
A combustor of the engine may include a combustor wall, which may be structured to withstand high temperatures. The second fluid may be circulated within the combustor wall and heat may be transferred from the combustor wall to the second fluid
Implementation Method 3
A closed Brayton cycle cooling system using a second fluid that circulates through the combustor wall to absorb heat
Data Source
AI summary
A cooling system for a high-speed vehicle may comprise a combustor wall at least partially enclosing a combustor and which is cooled using a coolant circulating in a Brayton cycle. The heated coolant may be expanded in a turbine, transfer heat to a fuel within a heat exchanger, and be compressed by a compressor before returning to the combustor wall. The combustor wall may be capable of withstanding high temperatures, higher than the temperature at which fuel coking may take place. Heat transfer takes place between the coolant and the combustor wall, and between the coolant and the fuel. A method of cooling an engine for a high-speed vehicle is also disclosed.