Cryogenic Fuel Bottoming Cycle for Aircraft Thermal Energy Recovery
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Solution Overview
Problem
Existing gas turbine engines waste significant thermal energy due to limitations in the capability of working fluids to absorb heat, limiting the amount of additional work that can be generated in a bottoming cycle.
Innovation Solution
Aircraft propulsion systems utilize a cryogenic fuel system that includes a cryogenic fuel storage tank, a bottoming compressor, a turboexpander, and a mixer to circulate and heat liquid fuel, converting it into a gaseous state for efficient energy recovery and power generation, with heat exchangers to optimize fuel flow and thermal energy utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional working fluid is used in the bottoming cycle, then the system structure is simple, but the thermal energy recovery capability is limited
Solution Approach 1:
The patent changes the physical and chemical parameters of the working fluid by using cryogenic fuel (such as liquid hydrogen or liquid methane) instead of conventional working fluids. This parameter change enables the working fluid to absorb thermal energy more effectively from the exhaust gas, thereby improving thermal energy recovery capability while managing system complexity through integrated design
Solution Approach 2:
The cryogenic fuel serves multiple functions: it acts as both the fuel for the combustor and the working fluid for the bottoming cycle. This multi-functionality allows the system to recover thermal energy effectively without adding separate complex subsystems, thus addressing the contradiction between energy recovery and system complexity
2Productivity
If the working fluid's heat absorption capability is increased, then additional work generation is improved, but the system complexity increases
Solution Approach 1:
The patent utilizes phase transitions of the cryogenic fuel (from liquid to gaseous state) as it absorbs thermal energy in the heat exchanger. This phase transition enables significant heat absorption capability, allowing the working fluid to absorb large amounts of thermal energy and generate additional work through expansion in the turbine, thereby improving productivity while managing system complexity
Solution Approach 2:
By changing the working fluid to cryogenic fuel with superior heat absorption properties, the system achieves enhanced additional work generation. The parameter change in working fluid selection enables more effective thermal energy recovery and conversion to mechanical work without requiring proportionally complex system modifications
3Loss of energy
If cryogenic fuel is used as working fluid, then thermal energy recovery is enhanced, but the fuel system complexity increases
Solution Approach 1:
The cryogenic fuel system is designed to serve dual purposes: supplying fuel to the combustor and providing working fluid for the bottoming cycle. This multi-functionality reduces the need for separate fuel delivery and working fluid circulation systems, thereby enhancing thermal energy recovery while mitigating fuel system complexity through integrated architecture
Solution Approach 2:
The patent merges the fuel supply system and the bottoming cycle working fluid system into a single integrated cryogenic fuel circulation system. The fuel pump, heat exchanger, and turbine are combined into a cohesive system where the same fluid serves both combustion and work generation functions, reducing overall system complexity while maintaining enhanced thermal energy recovery capability
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
Enhances engine efficiency by effectively recovering thermal energy and vaporizing liquid fuel, thereby generating additional shaft power and improving overall system performance.
Implementation Method 1
a mixer where the gaseous fuel flow mixes with and heats a liquid fuel flow to generate a gaseous fuel flow
Implementation Method 2
a cryogenic fuel storage tank where the gaseous fuel flow condenses to a liquid state
Implementation Method 3
a mixer where the gaseous fuel flow mixes with and heats a liquid fuel flow to generate a gaseous fuel flow
Implementation Method 4
a first heat exchanger where the gaseous fuel flow exhausted from the bottoming compressor is heated
Implementation Method 5
the second heat exchanger may communicate thermal energy from the exhaust gas flow into the gaseous fuel flow
Implementation Method 6
a turboexpander (e.g., a turbine) where the gaseous fuel flow from the first heat exchanger is expanded to generate shaft power
Data Source
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AI summary
An aircraft propulsion system (20) includes a core engine (25) that includes a combustor (26) where a cryogenic fuel is mixed with compressed air and ignited to generate an exhaust gas flow (90), a propulsive fan (22) driven by shaft power that is generated by the core engine (25), a cryogenic fuel system (62) that includes a cryogenic fuel storage tank (74), a fuel flow path (82) where a fuel flow (104) is circulated from upstream in a direction downstream toward the combustor (26) of the core engine (25), a bottoming compressor (84) where a gaseous fuel flow (104) is compressed, a first heat exchanger (78) where the gaseous fuel flow (104) exhausted from the bottoming compressor (84) is heated, a turboexpander (86) where the gaseous fuel flow (98) from the first heat exchanger (78) is expanded to generate shaft power (66), and a mixer (88) where the gaseous fuel flow (92) mixes with and heats a liquid fuel flow (70) to generate a gaseous fuel flow (104) for communication to the bottoming compressor (84).