Integrated Air Cycle Machine for Gas Turbine Cooling
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Solution Overview
Problem
Existing gas turbine engine cooling systems require large air cycle machines to provide cooled cooling air at or above compressor discharge pressure (P3), which is impractical for installation in the engine under-cowl area or on the aircraft.
Innovation Solution
Integration of an air cycle machine with a heat exchanger within the gas turbine engine, where the air cycle rotor is mechanically coupled to the engine rotor, allowing for compression and cooling of bleed air, enabling the provision of cooled cooling air at pressures above P3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a large air cycle machine is installed to provide cooled cooling air at or above P3 pressure, then the cooling performance is improved, but the device size and installation space requirements worsen
Solution Approach 1:
The air cycle machine is nested within the engine structure by integrating it into the accessory gearbox area and utilizing the engine's existing mechanical power. The ACM compressor and expander are positioned within the engine cowling space, with the expander mechanically coupled to the engine rotor to receive mechanical power directly from the engine, eliminating the need for external power sources and reducing overall system volume.
Solution Approach 2:
The air cycle machine serves multiple functions: it provides cooled cooling air for turbine components, utilizes waste heat from the heat exchanger for potential energy recovery, and integrates with the engine's existing mechanical and fluid systems. The system can operate in different modes depending on engine conditions, providing versatility in cooling applications.
2Volume of moving object
If an air cycle machine is integrated within the engine to reduce size, then the installation space is reduced, but the mechanical coupling complexity increases
Solution Approach 1:
The air cycle machine is merged with the engine's existing mechanical systems by coupling the expander to the engine rotor through the accessory gearbox. The ACM compressor is integrated with the engine's air supply system, drawing bleed air from the compressor and returning cooled air to the engine. This merging reduces the number of external connections and simplifies the overall system architecture.
3Temperature
If cooled cooling air is provided at high pressure (P3 or above), then the cooling effectiveness is improved, but the energy consumption increases
Solution Approach 1:
The system converts waste mechanical power from the engine rotor into useful cooling by driving the air cycle machine expander. The expander recovers energy from the high-pressure air and converts it to mechanical work, which drives the compressor. This energy recovery process reduces the net energy consumption while maintaining high cooling air pressure and temperature differential for effective cooling.
Solution Approach 2:
The air cycle machine operates autonomously using the engine's own mechanical power and air supply. The expander is mechanically coupled to the engine rotor, receiving power directly from the engine without external power sources. The system uses the engine's bleed air as the working fluid, eliminating the need for separate power and fluid supply systems.
Data Source
AI summary
A gas turbine engine includes: a compressor, a combustor, and a turbine arranged in sequential flow relationship along a primary flowpath, the turbine being connected in mechanical driving relationship to the compressor, so as to define at least one engine rotor that is rotatable about a centerline axis of the engine; a secondary flowpath connected in flow communication with the primary flowpath; and an air cycle machine including an air cycle rotor carrying an at least one air cycle compressor and at least one air cycle expander, wherein: the air cycle rotor is coupled in mechanical driving relationship with the at least one engine rotor; the air cycle rotor is coupled in fluid flow communication with the secondary flowpath; and the air cycle rotor is coupled in fluid flow communication with at least one heat exchanger.