Cooled Cooling Air System for Turbofan Engine Thermal Management
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Solution Overview
Problem
Conventional turbofan engine designs face limitations in propulsive efficiency due to thermal issues associated with gearboxes and high compressor exit temperatures, which restrict the ability to achieve desired compression ratios and thrust outputs while maintaining efficient engine performance.
Innovation Solution
Incorporating a cooled cooling air system that reduces the temperature of airflow using a heat exchanger and provides cooled air to turbine components, along with advanced gearbox configurations and temperature-resistant materials, to manage heat and increase compression efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional turbofan engine designs are used with standard gearboxes, then the engine structure is simpler and easier to manufacture, but propulsive efficiency is limited due to thermal issues and high compressor exit temperatures
Solution Approach 1:
The engine is divided into distinct thermal management zones with separate cooling circuits for different components (compressor, gearbox, turbine). This segmentation allows optimized cooling strategies for each component, improving overall propulsive efficiency while managing complexity through modular design.
Solution Approach 2:
The patent implements variable cooling parameters including temperature-controlled cooling air extraction at different compressor stages, adjustable cooling flow rates to the gearbox, and dynamic cooling activation based on operating conditions. These parameter changes optimize propulsive efficiency across different flight regimes.
2Power
If higher compression ratios are achieved to increase thrust output, then thrust performance is improved, but compressor exit temperatures become excessively high causing thermal management problems
Solution Approach 1:
Cooling air is extracted from the compressor at intermediate stages before the air reaches excessively high temperatures. This preliminary cooling action prevents thermal degradation of subsequent components while maintaining the high compression ratio needed for thrust generation.
Solution Approach 2:
A dedicated cooling air circuit acts as an intermediary between the high-temperature compression process and heat-sensitive downstream components. This intermediate cooling airflow manages temperature transitions, allowing high compression ratios without thermal damage to turbines and other components.
3Temperature
If advanced cooling systems are added to reduce compressor exit temperatures, then thermal management is improved, but device complexity and weight increase
Solution Approach 1:
The cooling air extracted from the compressor serves multiple functions: it cools the gearbox, conditions the air for combustion, and manages thermal loads in the turbine section. This multi-functionality reduces the need for separate cooling systems, minimizing added complexity while achieving effective thermal management.
Solution Approach 2:
The compressor itself generates the cooling air required for thermal management by extracting a portion of its own discharge air. This self-service approach eliminates the need for external cooling sources or additional power-consuming cooling systems, reducing overall system complexity.
4Reliability
If gearbox cooling is enhanced to manage thermal issues, then reliability is improved, but system complexity and weight increase
Solution Approach 1:
A pneumatic cooling system uses compressed air from the compressor to cool the gearbox, replacing heavier liquid cooling systems. This approach provides effective heat removal while minimizing weight addition, as the cooling medium is already available in the engine's air supply.
Solution Approach 2:
The cooling air that has passed through the gearbox and absorbed heat is not discarded but recovered and redirected to other thermal management functions or expelled through the exhaust. This recovery approach maximizes the utility of the cooling air, reducing the need for additional cooling mass.
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
The cooled cooling air system allows for increased turbofan engine thrust output while maintaining or improving propulsive efficiency, reducing compressor exit temperatures, and accommodating higher operating temperatures without excessive weight or complexity.
Implementation Method 1
the cooled cooling air system includes a heat exchanger configured to reduce a temperature of the cooling airflow
Implementation Method 2
provides the cooled cooling airflow to a turbine section of the turbomachine
Data Source
AI summary
A method of operating an engine is provided. The method includes operating the engine at a takeoff power level. Operating the engine at the takeoff power level includes operating the engine with a power performance indicator quantity (PIQPower) in a range of 1400 pounds per square inch (lbs/in2) to 2500 lbs/in2, wherein the power performance indicator quantity is determined according to:PIQPower=PIQHPTIPIQHPCE×N1N2×FnTotalAHPCE.