Turbofan Inner Fixed Structure for Variable Airflow Control
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Solution Overview
Problem
High bypass turbofan engines face challenges with increased weight, noise, and reduced efficiency due to large nacelle size, which affects performance during varying flight conditions beyond normal cruise operations.
Innovation Solution
A gas turbine engine system with a ducted inner fixed structure that modulates the discharge airflow cross-sectional area using selectively actuated duct nozzles with flaps, allowing for adjustment of airflow to optimize performance across different flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsive efficiency is improved, but nacelle size increases resulting in increased weight, noise and drag
Solution Approach 1:
The patent applies the dynamics principle by making the inner fixed structure movable through actuation mechanisms. The ducted passage's discharge airflow cross-sectional area is modulated by moving the inner fixed structure, allowing the system to dynamically adapt to different operating conditions. This resolves the contradiction by enabling a compact nacelle design that can expand its effective airflow area when needed, achieving high bypass efficiency without permanently increasing nacelle size and associated weight.
2Productivity
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsive efficiency is improved, but nacelle size increases resulting in increased noise
Solution Approach 1:
The movable inner fixed structure allows dynamic modulation of the discharge airflow cross-sectional area, enabling the engine to optimize noise characteristics during different flight conditions. By reducing the effective discharge area during conditions where noise is problematic, the system maintains propulsive efficiency while mitigating noise generation without requiring a permanently larger nacelle.
3Productivity
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsive efficiency is improved, but nacelle size increases resulting in increased drag
Solution Approach 1:
The patent utilizes the dynamics principle by implementing an actuated inner fixed structure that modulates the discharge airflow cross-sectional area. This allows the nacelle to maintain a compact size for reduced drag while dynamically expanding the effective airflow passage when high propulsive efficiency is required, thereby resolving the contradiction between drag reduction and efficiency maintenance.
4Productivity
If the turbofan engine is designed for maximum performance during normal cruise operation, then cruise efficiency is improved, but performance at non-cruise operating conditions deteriorates
Solution Approach 1:
The movable inner fixed structure enables dynamic adaptation to different flight conditions by modulating the discharge airflow cross-sectional area. During cruise, the structure is positioned to optimize efficiency, while during take-off, landing, and maneuver conditions, it can be actuated to different positions to optimize performance for those specific conditions, thereby resolving the contradiction between cruise optimization and overall adaptability.
Solution Approach 2:
The patent applies parameter changes by physically altering the discharge airflow cross-sectional area through movement of the inner fixed structure. This parameter modification allows the engine to transition between different performance states, optimizing for cruise efficiency when needed while maintaining adaptability for other flight conditions, thus resolving the contradiction between specialized optimization and general versatility.
Data Source
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AI summary
A gas turbine engine system includes a fan bypass passage (27), a core nacelle (28) having an inner fixed structure (40) within the fan bypass passage, a passage (42) extending through the inner fixed structure, and a duct nozzle (48). The passage includes an inlet (44) for receiving a fan airflow (F2) from the fan bypass passage and an outlet (46) for discharging the fan airflow. The duct nozzle includes a variable cross-sectional exit area (50) for controlling the fan airflow within the passage and is selectively moveable to influence the variable cross-sectional exit area.