Aircraft sCO2 Heat Engine Waste Heat Recovery
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Solution Overview
Problem
Aircraft engines face challenges in efficiently recuperating waste heat from exhaust gases without reducing thrust output or overall efficiency, as existing methods struggle to effectively convert this heat into useful work.
Innovation Solution
The use of a supercritical carbon dioxide (sCO2) heat engine, which is thermally coupled with the aircraft engine to convert waste heat into mechanical energy through a closed thermodynamic cycle, allowing for staged heat recuperation from multiple heat sources, including exhaust gas, coolant, and lubricating fluids, without significantly impacting thrust or efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heat is recuperated from exhaust gas in a turbofan engine, then energy efficiency is improved, but thrust output is reduced
Solution Approach 1:
A heat exchanger is introduced as an intermediary device to transfer heat from the exhaust gas to a working fluid (supercritical CO2) without directly cooling the exhaust gas flow that generates thrust. This allows heat recovery while maintaining the thermal energy available for thrust generation.
Solution Approach 2:
The patent replaces direct mechanical extraction of energy from exhaust gas (which would reduce thrust) with a thermal field-based approach using a heat exchanger and thermodynamic cycle, converting thermal energy to mechanical work through a separate closed loop system.
2Loss of energy
If a heat recovery system is added to the aircraft engine, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The heat recovery system is integrated with the existing aircraft engine systems by utilizing exhaust gas, coolant, and lubricating oil as heat sources, merging multiple thermal fields into a single combined heat recovery system that reduces overall complexity compared to separate systems.
Solution Approach 2:
The supercritical CO2 heat engine serves multiple functions: it drives a generator for electrical power, can drive a compressor for air supply, and can be coupled with propellers for direct propulsion, allowing a single heat recovery system to support multiple aircraft systems.
3Loss of energy
If supercritical CO2 is used as working fluid, then energy conversion efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The system operates with supercritical CO2 at specific pressure and temperature parameters (above critical point of 31.1°C and 73.8 bar) to achieve high conversion efficiency. The heat exchanger and turbine are designed to maintain these critical parameters throughout the thermodynamic cycle.
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 approach enhances energy efficiency by converting waste heat into useful mechanical work, reducing fuel consumption and operating costs, while providing a compact and environmentally friendly solution for aircraft power plants.
Implementation Method 1
a heat engine that is thermally coupled with the aircraft engine and that converts the heat into mechanical energy
Implementation Method 2
The heat from the exhaust gas of the aircraft engine (and/or other heat sources of the aircraft engine) may be transferred to a heat engine
Data Source
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AI summary
Aircraft power plants including combustion engines (18), and associated methods for recuperating waste heat from such aircraft power plants are described. A method includes transferring the heat rejected by the internal combustion engine (18) to supercritical CO2 (sCO2) used as a working fluid in a heat engine (20, 120, 220). The heat engine (20, 120, 220) converts at least some of the heat transferred to the sCO2 to mechanical energy to perform useful work onboard the aircraft.