Geared Turbofan Variable Nozzle for Fuel Efficiency
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Solution Overview
Problem
Direct drive turbofan engines face challenges in reducing turbofan pressure ratio, leading to increased engine weight and cost due to the need for additional compressor and turbine stages, which affects propulsive efficiency and fuel consumption.
Innovation Solution
A geared turbofan engine design where the fan is decoupled from the low spool and equipped with an adjustable nozzle exit area, utilizing a flow control device with hinged flaps and actuators to vary the nozzle exit area, allowing for independent control of fan speed and bypass airflow, thereby optimizing thrust and efficiency across different flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the turbofan pressure ratio is reduced to improve propulsive efficiency and fuel consumption, then fuel efficiency improves, but additional compressor and turbine stages are required which increases engine weight and cost
Solution Approach 1:
The engine is divided into separate fan and core spools that can rotate at different speeds, with the fan decoupled from the low spool. This segmentation allows independent optimization of fan pressure ratio for fuel efficiency while maintaining appropriate core spool characteristics, eliminating the need for additional compressor and turbine stages
Solution Approach 2:
The fan nozzle exit area is made variable through flow control devices with hinged flaps and actuators, allowing dynamic adjustment of the nozzle area. This enables the fan to operate at optimal pressure ratios across different flight conditions, achieving improved fuel efficiency without requiring fixed additional stages that would increase engine weight
2Use of energy by moving object
If the fan pressure ratio is reduced to improve propulsive efficiency, then propulsive efficiency improves, but additional compressor and turbine stages must be added which increases device complexity
Solution Approach 1:
The fan is decoupled from the low spool, creating independent rotational systems. This allows the fan to operate at reduced pressure ratios for improved propulsive efficiency while the core spool maintains appropriate compression, eliminating the need for additional compressor and turbine stages that would increase device complexity
Solution Approach 2:
Variable fan nozzle exit area through flow control devices enables dynamic optimization of fan operating conditions. The nozzle can be adjusted to maintain optimal airflow and pressure ratios across different flight conditions, achieving improved propulsive efficiency without requiring fixed additional stages
3Adaptability or versatility
If the nozzle exit area is made variable to manipulate engine operating conditions, then operating flexibility improves, but device complexity increases due to additional control structures
Solution Approach 1:
The fan nozzle exit area is made variable through flow control devices with hinged flaps and actuators, allowing dynamic adjustment of the nozzle area to manipulate engine operating conditions. This enables the engine to adapt to different flight conditions and optimize performance while maintaining manageable structural complexity through efficient design
Data Source
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AI summary
A turbofan engine (10) is provided that includes a fan nacelle (34) surrounding a core nacelle (12). The core nacelle (12) houses a spool (14). The fan (34) and core (12) nacelles provide a bypass flow path (39) having a nozzle exit area (40). A turbofan (20) is arranged within the fan nacelle (34) upstream from the core nacelle (12). A flow control device (41) is adapted to effectively change the nozzle exit area (40) to obtain a desired operating condition for the turbofan engine (10). A gear train (22) couples the spool (14) and turbofan (20) for reducing a turbofan rotational speed relative to a spool rotational speed. A controller (50) is programmed to respond to at least one sensor (52-60). The controller (50) is programmed to effectively control the nozzle area (40).