Hybrid Propulsion Cooling System for Thermal Soakback Mitigation
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Solution Overview
Problem
Gas turbine engines experience thermal soakback during shutdown, leading to inadequate cooling and increased weight, cost, and complexity due to reliance on auxiliary power units or batteries for electric power at altitude, where natural convection and thermal radiation are insufficient.
Innovation Solution
A hybrid propulsion system incorporating a gas turbine engine and a secondary engine, with a pressurized tank containing a cooling fluid that expands through a turbine to generate electricity and cool the engine, while isolating the gas turbine engine from ambient air to prevent heat transfer and thermal soakback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the gas turbine engine is shut down and natural convection and thermal radiation are used for cooling, then the cooling system is simple, but the cooling effect is insufficient leading to thermal soakback
Solution Approach 1:
The system stores cryogenic cooling fluid in a pressurized tank before shutdown occurs. When shutdown happens, the pre-stored cooling fluid is automatically released through the expansion valve to provide immediate cooling, preventing thermal soakback before it can occur rather than relying on slow natural convection.
Solution Approach 2:
The cooling fluid undergoes phase transition from liquid to gas when it passes through the expansion valve. This phase change absorbs significant heat from the engine components, providing rapid and effective cooling during shutdown when natural convection is insufficient.
2Use of energy by moving object
If auxiliary power units or batteries are used to provide electric power during shutdown, then continuous power is available, but system weight and complexity increase
Solution Approach 1:
The cryogenic cooling fluid system serves dual functions: it cools the engine during shutdown and simultaneously drives the turbine to generate electric power. This eliminates the need for separate auxiliary power units or batteries, reducing system weight and complexity while maintaining continuous power availability.
Solution Approach 2:
The cooling fluid itself becomes the energy source for power generation. As the fluid expands and cools the engine, it naturally drives the turbine connected to the generator, making the system self-sufficient for both cooling and power needs without external auxiliary equipment.
3Loss of energy
If the gas turbine engine operates without isolation from ambient air, then heat transfer to ambient is efficient, but thermal soakback to sensitive components occurs during shutdown
Solution Approach 1:
The engine system is divided into thermal zones: hot sections (turbine, combustor) and sensitive sections (fuel injectors, electrical wiring). The cooling fluid is directed specifically to protect sensitive components from thermal soakback, while hot sections continue to dissipate heat to the ambient environment through the exhaust path.
Solution Approach 2:
The cryogenic cooling fluid acts as an intermediary between the hot engine components and sensitive components. It absorbs excess heat from hot sections and redirects thermal energy away from temperature-sensitive components, preventing thermal soakback while maintaining overall heat dissipation.
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
Effectively cools the gas turbine engine during shutdown, reduces weight and complexity by eliminating the need for auxiliary power units, and provides continuous electric power by converting the expansion of cooling fluid into electricity.
Implementation Method 1
The cooling fluid may expand through and rotate the turbine
Implementation Method 2
The rotation of the turbine may generate electricity
Implementation Method 3
providing a cooling fluid from a pressurized tank to the gas turbine engine, impinging the gas turbine engine with the cooling fluid to cool the gas turbine engine
Implementation Method 4
heat from the turbine and/or combustor section may soak toward components like fuel injectors, electrical wiring, etc.
Implementation Method 5
The expansion valve may be in fluid communication with the pressurized tank and the core passage
Implementation Method 6
The cooling fluid may expand through and rotate the turbine
Data Source
AI summary
A hybrid propulsion system is provided. The system may comprise a gas turbine engine and a secondary engine, an inlet, an exhaust, a pressurized tank, and an expansion valve. The inlet may be in fluid communication with the ambient environment. The gas turbine engine may have a core passage including a compressor, a combustion chamber, and a turbine. The core passage may be in selective fluid communication with the inlet. The exhaust may be in fluid communication with the ambient environment and the core passage. The pressurized tank may be located upstream of the core passage. The pressurized tank may contain a cooling fluid. The expansion valve may be in fluid communication with the pressurized tank and the core passage. The pressurized tank may provide cooling fluid to the core passage to cool the gas turbine engine during operation of the secondary engine.