Variable Area Fan Nozzle Ice Management
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Solution Overview
Problem
Gas turbine engine fan operability is compromised by fixed nozzle area designs, leading to performance penalties and challenges in managing fan flutter, surge, and stall, especially under varying flight conditions and icing scenarios.
Innovation Solution
A variable area fan nozzle system that adjusts its position based on icing conditions and airspeed, using movable flaps and a controller to alter the fan nozzle exit area, ensuring adequate operability margin and optimizing engine performance across different flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed nozzle area design is used, then the engine structure is simple, but the fan operability is compromised leading to performance penalties and challenges in managing fan flutter, surge, and stall
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed nozzle from a static structure to a dynamic one with movable flaps that can adjust the nozzle exit area. The flap mechanism allows the nozzle area to vary during engine operation, enabling adaptation to different flight conditions and improving fan operability margins while managing fan flutter, surge, and stall conditions.
Solution Approach 2:
The patent implements parameter changes by modifying the nozzle exit area parameter through movable flaps. By changing the effective nozzle area parameter in response to operating conditions (including icing conditions), the system optimizes fan operability and engine performance across the flight envelope without requiring complete redesign of the entire nozzle structure.
2Adaptability or versatility
If the fan operating line is compromised to accommodate various engine operating conditions, then the engine can operate across the flight envelope, but fuel consumption increases and performance is reduced
Solution Approach 1:
The variable area nozzle provides dynamic adaptation capability, allowing the engine to maintain optimal performance across different flight conditions without compromising fuel efficiency. By adjusting the nozzle area in real-time, the system preserves the fan operating line characteristics needed for various operating conditions rather than designing for a compromised average performance.
Solution Approach 2:
The system changes the nozzle exit area parameter to optimize engine performance for specific operating conditions. This allows the engine to achieve better fuel consumption characteristics at each operating point by adjusting the nozzle area rather than being constrained by a fixed design that must accommodate all conditions equally.
3Productivity
If flaps are kept open at low air speeds, then the nozzle exit area is maximized for performance, but ice accumulation becomes more likely to affect operation
Solution Approach 1:
The system dynamically adjusts flap position based on detected icing conditions. When ice accumulation is detected or anticipated at low air speeds, the control system modifies the flap position to reduce ice accumulation effects while managing the resulting impact on nozzle exit area and engine performance.
Solution Approach 2:
The system uses feedback from icing condition detection to adjust flap operation. By monitoring conditions that indicate ice accumulation risk and responding with appropriate flap position adjustments, the system manages the harmful effects of ice while attempting to maintain acceptable engine performance.
Data Source
AI summary
A method of managing a gas turbine engine variable area fan nozzle includes the steps of operating a variable area fan nozzle according to a first operating schedule. An icing condition input is evaluated to determine the likelihood of ice presence. The first operating schedule is altered to provide a variable area fan nozzle position if ice is likely present or actually present to provide an icing operating schedule different than the first operating schedule. The first operating schedule corresponds to the flaps at least partially open at air speeds below a first airspeed. The altering step includes closing the flaps below the first airspeed as part of the icing operating schedule. The variable area fan nozzle position is adjusted according to the icing operating schedule. A fan is arranged in a fan nacelle that includes a flap configured to be movable between first and second positions. An actuator is operatively coupled to the flap.