Augmentor Flow Splitter Duct for Gas Turbine Cooling
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Solution Overview
Problem
Gas turbine engine augmentors face reduced efficiency due to high air flow requirements for cooling, which decreases augmentor temperature capability and efficiency, and uncontrolled screech-induced vibrations lead to high-cycle fatigue, necessitating effective screech suppression.
Innovation Solution
The implementation of an augmentor flow splitter duct system that directs a portion of fan bypass air into an annular augmentor liner cooling flow path and maintains a positive backflow pressure margin, reducing the amount of air needed for screech suppression and cooling, while optimizing the design of screech suppression air holes and film cooling holes to minimize air flow losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If highly effective film-cooling structures are used to cool the augmentor liner, then the metal temperature shielding is improved, but the air flow consumption increases which reduces augmentor efficiency
Solution Approach 1:
The cooling air flow is segmented into different functional paths: a first cooling air flow path for film cooling the liner, and a second cooling air flow path for cooling the exhaust nozzle. This segmentation allows optimized cooling distribution, ensuring adequate protection while minimizing total air consumption by directing flow where most needed.
Solution Approach 2:
A flow splitter duct is introduced as an intermediary component that receives cooling air and distributes it between the liner film cooling holes and exhaust nozzle cooling holes. This mediator enables precise control over cooling air allocation, allowing the system to achieve effective temperature shielding with reduced overall air flow requirements.
2Reliability
If cooling air is used to suppress screech in the augmentor, then screech-induced vibrations are reduced, but the air flow required for cooling increases which decreases augmentor efficiency
Solution Approach 1:
The cooling air flow serves multiple functions simultaneously: it provides film cooling to protect the liner from hot combustion gases, cools the exhaust nozzle, and suppresses screech vibrations. By making the cooling air flow multi-functional, the system achieves reliable screech suppression without requiring additional dedicated air flow, thereby maintaining augmentor efficiency.
Solution Approach 2:
The system optimizes cooling air flow parameters by controlling the proportion of air directed to different cooling paths. By adjusting flow distribution parameters and maintaining appropriate pressure ratios between cooling zones, the system achieves effective screech suppression while minimizing total air consumption, thus preserving augmentor efficiency.
3Temperature
If fan bypass air is used for cooling the augmentor liner, then cooling effectiveness is improved, but the discharge gases available for augmentor combustion are reduced
Solution Approach 1:
The cooling air requirement is segmented and satisfied primarily through recirculated cooling air from the exhaust zone rather than relying heavily on fan bypass air. This segmentation allows the system to maintain cooling effectiveness while preserving fan bypass air for combustion, as the recirculated air provides sufficient cooling with minimal impact on combustion gas availability.
Solution Approach 2:
The cooling system utilizes recirculated cooling air that is generated within the exhaust zone itself, creating a self-sustaining cooling circuit. This self-service approach reduces dependence on external fan bypass air, allowing the discharge gases to be fully utilized for combustion while maintaining adequate cooling effectiveness through internal recirculation.
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 reduces the air flow required for screech suppression and cooling, enhancing overall engine efficiency and extending the life of augmentor components by effectively managing screech-induced vibrations and maintaining acceptable metal temperatures.
Implementation Method 1
efficient augmentor cooling liner should provide casing thermal shielding to maintain acceptable levels of metal temperature consistent with durability and life requirements for the augmentor
Implementation Method 2
directing a portion of fan bypass air into a generally annular augmentor liner cooling flow path between an augmentor outer casing and an annular augmentor liner
Implementation Method 3
maintaining positive backflow pressure margin between air flow within the augmentor splitter flow path and the augmentor liner cooling flow path
Implementation Method 4
Intense combustion induced, high frequency pressure oscillations are generated under certain operating conditions in the augmentor and are known in the art as 'screech'. Uncontrolled screech reduces the high-cycle fatigue life of the augmentor components due to screech-induced vibration
Data Source
AI summary
A gas turbine engine augmentor includes an augmentor outer casing 502 and an annular augmentor liner 504 disposed radially within and radially separated from the augmentor outer casing 502 to form a generally annular augmentor liner cooling flow path 500 between the augmentor casing and the annular augmentor liner, and an augmentor flow splitter duct 506 disposed at the upstream end of the augmentor liner and radially between the augmentor outer casing 502 and the annular augmentor liner 504 and defining a splitter flow path 520 between the annular augmentor liner 504 and the annular augmentor flow splitter duct 506. A method of operating a gas turbofan engine including an augmentor includes directing a portion of fan bypass air into a generally annular augmentor liner cooling flow path 500 between an augmentor outer casing 502 and an annular augmentor liner 504, directing a portion of the air in the augmentor liner cooling flow path 500 into a splitter flow path 520 disposed radially outside the augmentor liner 504 and maintaining positive backflow pressure margin between air flow within the splitter flow path and the augmentor liner cooling flow path 500.