Boost Compressor for Gas Turbine Cooling Air Pressure
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Solution Overview
Problem
The increasing cooling loads in gas turbine engines, particularly due to gear reductions that cause turbines to rotate faster, result in insufficient cooling air pressure for effective cooling of high-pressure turbine components, leading to potential durability issues and reduced thermal efficiency.
Innovation Solution
A boost compressor driven by a low speed rotor spool is used to increase the pressure of cooling air, which is then passed through a second heat exchanger before being delivered to the high-pressure turbine area, and a clutch mechanism is introduced to disconnect the boost compressor when higher pressure is not necessary, allowing for efficient modulation of cooling air flow based on operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gear reduction is introduced between the fan drive turbine and the fan, then the fan can be driven at lower speeds, but the turbine rotation speed increases leading to higher cooling loads that cannot be met by existing cooling air systems
Solution Approach 1:
A boost compressor is introduced as an intermediary device between the cooling air source and the high-pressure turbine components. This boost compressor receives cooling air from the compressor outlet and pressurizes it before delivery, enabling the cooling system to meet the increased cooling demands created by the gear reduction system.
2Quantity of substance
If cooling air is tapped downstream of the high pressure compressor, then the cooling air is readily available, but the pressure is insufficient to effectively cool the high pressure turbine components
Solution Approach 1:
The boost compressor acts as a mediator that takes the readily available cooling air from the compressor outlet and increases its pressure to the required level for effective high-pressure turbine component cooling, thus resolving both the availability and pressure requirements.
Solution Approach 2:
Cooling air is extracted (tapped) from the compressor outlet where it is readily available, and then separately pressurized by the boost compressor to achieve the necessary pressure for high-pressure turbine cooling, decoupling the quantity availability from the pressure requirement.
3Reliability
If the boost compressor is continuously engaged to provide pressurized cooling air, then cooling effectiveness is maintained, but fuel efficiency decreases during operations where high pressure cooling is not necessary
Solution Approach 1:
The boost compressor is made dynamic through the clutch mechanism, allowing it to be selectively engaged and disengaged based on operational conditions. This enables the system to maintain cooling effectiveness when needed while improving fuel efficiency when the high-pressure cooling demand is low or absent.
Solution Approach 2:
The control system monitors engine operating conditions and automatically engages or disengages the boost compressor as needed, allowing the system to self-regulate and optimize the balance between cooling effectiveness and fuel efficiency without continuous manual intervention.
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 provides cooler and pressurized cooling air, enhancing turbine durability and reducing cooling flow demands, while also improving fuel efficiency by selectively engaging/disengaging the boost compressor based on power operation conditions.
Implementation Method 1
A boost compressor driven by a low speed rotor spool is used to increase the pressure of cooling air
Implementation Method 2
the cooling air is then passed through a second heat exchanger before being delivered to the high-pressure turbine area
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A gas turbine engine (100) has a compressor section with a low pressure compressor (104) and a high pressure compressor (102). The high pressure compressor (102) has a downstream most location (106). A cooling air system includes a tap (114) from a location upstream of the downstream most location (106). The tap (114) passes air to a boost compressor (118) and a heat exchanger (116), which passes the air back to a location to be cooled. The boost compressor (118) is driven by a shaft (113) which drives the lower pressure compressor (104).