Cooling Compressor Starter for Gas Turbine Engine
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Solution Overview
Problem
Current gas turbine engines face challenges in providing effective cooling to high-pressure turbine sections due to the limitations of existing heat exchanger technology, which struggles with high temperatures and pressures, especially as temperatures at the downstream discharge of the high-pressure compressor exceed 1350°F (732°C).
Innovation Solution
The implementation of a cooling compressor system that includes a centrifugal compressor impeller driven by the turbine section, with an auxiliary power unit providing pressurized air and variable vanes to direct airflow efficiently through a heat exchanger, allowing for the use of cooler air from an upstream compressor stage to be compressed and delivered to the high-pressure turbine, thereby reducing the workload and improving cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If air is tapped from the downstream discharge of the high-pressure compressor, then the cooling air pressure is sufficient for the turbine section, but the air temperature becomes too high (greater than or equal to 1350°F) to provide effective cooling
Solution Approach 1:
The cooling air system is segmented into multiple sources: cooler air from an upstream compressor stage and additional pressurized air from a heat exchanger. This segmentation allows the system to combine air at different temperatures and pressures to achieve the desired cooling effect without exceeding temperature limits.
Solution Approach 2:
A heat exchanger is introduced as an intermediary device to cool the high-temperature air from the downstream compressor discharge. The heat exchanger transfers heat from the cooling air to the bypass air, enabling the air to be cooled before entering the turbine section while maintaining sufficient pressure.
2Ease of operation
If a separate air turbine starter is used to begin rotation of engine components, then starting capability is provided, but device complexity and packaging space increase
Solution Approach 1:
The cooling compressor is merged with the air turbine starter function. The cooling compressor's rotor serves dual purposes: it compresses air for cooling during normal operation and acts as a turbine starter during engine startup. This consolidation eliminates the need for a separate air turbine starter, reducing component count and simplifying the overall system.
Solution Approach 2:
The cooling compressor is designed with multi-functionality, serving both as a compression device for cooling air generation and as a starter motor during engine startup. The same rotor and housing structure perform different functions at different operational phases, improving system efficiency and reducing complexity.
3Stress or pressure
If high pressure air is delivered to the turbine at high temperatures, then the cooling load on the turbine section increases, but component stress and thermal damage risk increase
Solution Approach 1:
Cooling action is performed preliminarily before the air enters the turbine section. The heat exchanger cools the air in advance, and the variable vanes on the cooling compressor impeller optimize compression to deliver cooled air at the required pressure level before it reaches the turbine, preventing thermal stress accumulation.
Solution Approach 2:
Variable vanes are incorporated on the cooling compressor impeller to dynamically adjust the compression process. These vanes can change their angle to optimize airflow and compression ratio under different operating conditions, enabling the system to deliver air at the optimal combination of pressure and temperature for turbine cooling.
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 solution effectively reduces the workload required to compress air to the desired pressure level, allowing for higher pressure air to be delivered to the turbine at significantly lower temperatures, enhancing cooling efficiency and reducing the stress on engine components, while also eliminating the need for a separate air turbine starter, resulting in improved engine performance and packaging efficiency.
Implementation Method 1
The compressed air passes into a heat exchanger where it is cooled by the bypass air
Implementation Method 2
a cooling compressor system that includes a centrifugal compressor impeller driven by the turbine section
Data Source
Figure 1
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Figure 4
AI summary
A gas turbine engine comprises a high pressure compressor (108) with a downstream discharge, and more upstream locations. A turbine section has a high pressure turbine (117). A tap (110) taps air from at least one of the more upstream locations in the compressor section, passes the tapped air through a heat exchanger (112) and then to a cooling compressor (114). The cooling compressor (114) compresses air downstream of the heat exchanger (112), and delivers air into the high pressure turbine (117). The cooling compressor (114) is connected to be driven with at least one rotor in the main compressor section. A source (165) of pressurized air is selectively sent to the cooling compressor to drive a rotor (176) of the cooling compressor (114) to rotate, and to in turn drive the at least one rotor of the main compressor section at start-up of the gas turbine engine.