Duct Burner in Turbofan Bypass for Thrust Augmentation
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Solution Overview
Problem
Existing gas turbine engines face challenges in meeting diverse propulsion needs, particularly in 'hot day' and high altitude conditions with short runways, due to limitations in fan diameter and length, and current augmentation systems are too long and not adaptable for exhaust system shaping, while also increasing weight and complexity.
Innovation Solution
A duct burner system is integrated into the bypass duct of a gas turbine engine upstream of the exit plane, combining the primary and secondary flows of pressurized combustion gases for efficient thrust augmentation, with a supplementary fan stage and adjustable nozzle designs to optimize thrust and fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If current augmentation systems are used to increase take-off thrust, then thrust increase is achieved, but engine length increases and exhaust system shaping becomes difficult
Solution Approach 1:
The duct burner is nested within the bypass duct of the turbofan engine, utilizing the existing bypass duct space for thrust augmentation. This integration allows the augmentation system to be contained within the engine's existing envelope, avoiding increases in engine length while still providing the required thrust increase.
Solution Approach 2:
The bypass duct serves multiple functions: it provides the bypass flow path for the turbofan engine and simultaneously houses the duct burner for thrust augmentation. This multi-functionality eliminates the need for separate augmentation system components that would extend the engine length.
2Power
If current augmentation systems are used to increase take-off thrust, then thrust increase is achieved, but device complexity and weight increase
Solution Approach 1:
The bypass duct is designed to serve dual purposes: as the bypass flow path and as the housing for the duct burner. This eliminates the need for separate augmentation system components, reducing overall system complexity and weight while maintaining thrust augmentation capability.
Solution Approach 2:
The augmentation system is merged with the bypass duct structure, combining the thrust augmentation function with the existing bypass flow path. This integration reduces the number of separate components and simplifies the overall system architecture.
3Length of moving object
If non-augmented higher fan pressure ratio engines are used to meet thrust requirements within diameter and length constraints, then diameter and length constraints are satisfied, but cruise segment specific fuel consumption increases
Solution Approach 1:
The engine operates in two dynamic modes: a cruise mode with lower fan pressure ratio for optimal fuel efficiency, and a take-off mode with duct burner augmentation for maximum thrust. This dynamic operation allows the engine to optimize fuel consumption during cruise while meeting thrust requirements during take-off without permanently increasing engine length or weight.
Solution Approach 2:
The fan pressure ratio is varied between cruise and take-off operations. During cruise, a lower fan pressure ratio is used for optimal fuel efficiency. During take-off, the duct burner is activated to provide the necessary thrust augmentation, allowing the use of a lower fan pressure ratio overall while still meeting peak thrust requirements.
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 duct burner system provides a modest 15-25% increase in take-off thrust while maintaining engine length and shaping compatibility, achieving a more efficient cruise cycle with reduced specific fuel consumption and adaptable exhaust system design.
Implementation Method 1
a duct burner disposed in the bypass duct, upstream of the exit plane, for generating a second flow of pressurized combustion gases
Implementation Method 2
combining the first and second flows of pressurized combustion gases in to a mixed exhaust flow downstream of the exit plane
Data Source
AI summary
A gas turbine engine includes a turbomachinery core operable to generating a first flow of pressurized combustion gases, the core having an exit plane; a fan disposed upstream of the core adapted to extract energy from the core and generate a first flow of pressurized air; a bypass duct surrounding the core which receives a portion of the flow of pressurized air from the fan; a duct burner disposed in the bypass duct, upstream of the exit plane, for receiving the first flow of pressurized air and generating a second flow of pressurized combustion gases; and an exhaust duct disposed downstream of the core and operable to receive and the first and second flows of pressurized combustion gases and to discharge the combined flows downstream.