Integrated APU and Waste Heat Recovery Using Supercritical CO2
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Solution Overview
Problem
Gas turbine engines suffer from inefficiency due to wasted heat energy being expelled without providing additional work, leading to reduced engine efficiency and increased fuel consumption.
Innovation Solution
A waste heat management system that integrates an auxiliary power unit (APU) with a gas turbine engine, utilizing a supercritical CO2 cycle to recover waste heat through a series of heat exchangers and turbines, allowing for the generation of mechanical or electrical work even when the main engine is off, by directing a working fluid through a secondary heat recovery heat exchanger during engine shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If waste heat is expelled without recovery, then the system is simple, but engine efficiency is reduced and fuel consumption increases
Solution Approach 1:
The patent merges the APU system and waste heat recovery system into a single integrated unit. The APU turbine and compressor are combined with the waste heat recovery turbine and heat exchangers, allowing the same components to perform dual functions: generating power during engine operation and recovering waste heat during ground operations, thereby reducing overall system complexity while addressing energy loss
Solution Approach 2:
The integrated system performs multiple functions: it generates auxiliary power when the engine is running, recovers waste heat during ground operations, and provides cooling through the heat exchangers. This multi-functionality eliminates the need for separate APU and waste heat recovery systems, resolving the contradiction between energy recovery and system complexity
2Power
If a separate APU system is installed, then power is available during engine shutdown, but component count and weight increase
Solution Approach 1:
The patent combines the APU functionality with the waste heat recovery system components. The same turbine, compressor, and heat exchangers serve both as waste heat recovery devices during engine operation and as APU power generation components during ground operations, eliminating the need for a separate APU system and thereby reducing weight
Solution Approach 2:
The integrated system provides auxiliary power during engine shutdown through the APU turbine while simultaneously serving as a waste heat recovery system during engine operation. This dual functionality achieves the required power availability without adding the weight of a separate APU system
3Use of energy by moving object
If waste heat is recovered through heat exchangers, then energy efficiency improves, but system complexity and component count increase
Solution Approach 1:
The patent integrates the waste heat recovery heat exchangers into the APU system architecture. The heat exchangers are positioned to recover heat from engine exhaust and cooling air, and this recovered heat is utilized by the APU turbine and working fluid cycle, thereby improving energy efficiency while avoiding the complexity of a completely separate heat recovery system
Solution Approach 2:
The heat exchangers serve dual purposes: they recover waste heat from the engine during operation and simultaneously provide thermal energy to the APU working fluid for power generation during ground operations. This multi-functionality improves energy efficiency without proportionally increasing system complexity
4Loss of energy
If the working fluid is directed through multiple heat exchangers, then more waste heat is recovered, but the system becomes more complex
Solution Approach 1:
The patent combines multiple heat recovery functions into a single integrated working fluid path. The working fluid passes through heat exchangers that simultaneously recover heat from engine exhaust, cooling air, and other thermal sources, maximizing waste heat recovery while maintaining a unified fluid path rather than multiple separate systems
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 system enhances engine efficiency by converting waste heat into work, reducing fuel burn and weight, while potentially eliminating the need for separate APU systems, thereby improving overall aircraft performance and reducing component count.
Implementation Method 1
a recuperating heat exchanger that is a working fluid-to-working fluid heat exchanger
Implementation Method 2
a heat rejection heat exchanger that is thermally connected to a portion of the cooling duct, the heat rejection heat exchanger being a working fluid-to-air heat exchanger
Implementation Method 3
a heat recovery heat exchanger being a working fluid-to-exhaust heat exchanger
Implementation Method 4
an auxiliary power unit (APU) system having a secondary heat recovery heat exchanger that is a working fluid-to-APU exhaust heat exchanger
Implementation Method 5
the working fluid is supercritical CO 2 (sCO 2 )
Implementation Method 6
The expansion of the combustion products drives the turbine section to rotate
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Waste heat management systems are described. The waste heat management systems include a turbine engine (500) having a compressor section, a combustor section, a turbine section, and a nozzle (520). The compressor section, the combustor section, the turbine section, and the nozzle define a core flow path that expels through the nozzle (520). The waste heat management systems also include an auxiliary power unit (APU) system (540) and a waste heat recovery system (502) operably connected to the APU system (540). The APU system is integrated into a working fluid flow path (522) of the waste heat recovery system (502).