Intercooled Cooling Air for Gas Turbine Engine Efficiency
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Solution Overview
Problem
Current gas turbine engine designs face challenges in providing effective cooling to high-pressure turbine components due to increasing overall pressure ratios, as existing heat exchanger technologies struggle with high temperatures and pressures, particularly when air temperatures approach 1350° F, limiting their efficiency and durability.
Innovation Solution
The implementation of a system that includes a first tap for delivering air at a lower pressure, a heat exchanger positioned in the bypass duct, and a cooling compressor that compresses air to a higher pressure, with a valve assembly to selectively choose between air from the tap and the high-pressure feed for delivery to the turbine section, allowing for efficient cooling and reduced energy expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air is tapped from the downstream most end of the compressor section, then the cooling air pressure is sufficient for turbine cooling, but the air temperature is elevated making heat exchanger cooling less effective
Solution Approach 1:
The compressor section is divided into multiple tapping points along its length. The system taps cooling air from intermediate stages rather than the final discharge, obtaining air at lower temperatures while maintaining adequate pressure through strategic placement of multiple taps at different compressor stages
Solution Approach 2:
The heat exchanger acts as an intermediary device positioned in the bypass duct to cool the tapped air before it reaches the turbine section. By introducing this intermediate cooling stage, the system reduces the temperature of compressor air without requiring it to come from the lowest pressure point
2Temperature
If a heat exchanger is used to cool the air, then the cooling effectiveness improves, but the system complexity and energy expenditure increase
Solution Approach 1:
The heat exchanger utilizes the cold bypass air flow as a free cooling source. The bypass duct provides a continuous stream of relatively cool air that automatically absorbs heat from the compressor air in the heat exchanger without requiring additional energy input, making the cooling system self-sufficient
Solution Approach 2:
The system merges the compressor air flow path with the bypass air flow path through the heat exchanger. By combining these two air streams thermally rather than requiring separate cooling systems, the design reduces overall energy expenditure while maintaining effective turbine cooling
3Power
If the overall pressure ratio is increased, then the engine power and efficiency improve, but the turbine component temperatures increase beyond heat exchanger capabilities
Solution Approach 1:
The system performs preliminary cooling of the compressor air before it enters the turbine section. By pre-cooling the air through the heat exchanger using bypass air, the system prepares the cooling air in advance, allowing higher pressure ratios to be used in the compressor without exceeding thermal limits in the turbine
Solution Approach 2:
The system adds a thermal management dimension to the pressure ratio optimization problem. Instead of solely increasing pressure ratio to improve power, the design introduces a bypass air cooling pathway that enables higher pressure ratios by managing the thermal dimension separately, thus decoupling power increase from temperature increase
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 configuration enables efficient cooling of turbine components by utilizing air at lower temperatures and pressures, reducing the work required to compress air, leading to improved engine efficiency and increased power density while extending the lifespan of heat exchanger components.
Implementation Method 1
a heat exchanger positioned in the bypass duct
Implementation Method 2
The air from the downstream most end of the compressor section is at elevated temperatures
Implementation Method 3
a cooling compressor that compresses air to a higher pressure
Data Source
AI summary
A gas turbine engine includes a plurality of rotating components housed within a compressor section and a turbine section. A first tap is connected to the compressor section and configured to deliver air at a first pressure. A heat exchanger is connected downstream of the first tap and configured to deliver air to an aircraft fuselage. A cooling compressor is connected downstream of the heat exchanger. A high pressure feed is configured to deliver air at a second pressure which is higher than the first pressure. The cooling compressor is configured to deliver air to at least one of the plurality of rotating components. A valve assembly that can select whether air from the first tap or air from the high pressure feed is delivered to the aircraft pneumatic system.