Adaptive Fan System for Variable Cycle Turbofan Engine
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Solution Overview
Problem
Military gas turbine engines face inefficiencies in both specific fuel consumption and power-to-weight ratio compared to commercial engines, necessitating a variable cycle design that achieves low fuel consumption and high thrust levels for supersonic flight and maneuvering capabilities.
Innovation Solution
A variable cycle gas turbine engine with an adaptive fan system, featuring a transmission system that selectively varies the speed of a variable-speed fan stage relative to a base fan stage, allowing operation in high thrust, low bypass ratio modes or high efficiency, high bypass ratio modes by diverting airflow through separate bypass ducts, maintaining constant inlet flow and optimizing engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed bypass ratio design is used, then the engine structure is simple, but the engine cannot achieve both low fuel consumption and high thrust levels across different flight conditions
Solution Approach 1:
The patent implements a variable cycle engine with two fan stages that can operate at different speeds, allowing the bypass ratio to be dynamically adjusted. The first fan stage is directly coupled to the turbine, while the second fan stage is coupled through a transmission system, enabling independent speed control to adapt to different flight conditions (supersonic, subsonic, cruise, maneuvering).
Solution Approach 2:
The engine is divided into two independent fan stages with separate bypass ducts. The first fan stage handles core airflow while the second fan stage handles bypass airflow, allowing independent control of each stage's speed and flow rate to optimize performance across different operating modes.
2Use of energy by moving object
If a high bypass ratio is used, then fuel consumption is reduced, but thrust level and power-to-weight ratio decrease
Solution Approach 1:
The transmission system allows the second fan stage to operate at variable speeds independent of the first fan stage. During cruise conditions, the second fan stage operates at high speed with high bypass ratio for fuel efficiency. During supersonic or maneuvering conditions, the second fan stage speed is reduced or stopped, lowering bypass ratio and increasing thrust availability.
3Power
If a low bypass ratio is used, then thrust level and power-to-weight ratio are increased, but fuel consumption efficiency decreases
Solution Approach 1:
The variable speed transmission system enables the engine to switch between low bypass ratio mode (high thrust, lower efficiency) and high bypass ratio mode (lower thrust, high efficiency) by adjusting the second fan stage speed according to flight conditions, optimizing the trade-off between thrust and fuel consumption dynamically.
4Productivity
If the fan speed is varied during operation, then efficiency and transient characteristics are improved, but spool speed changes increase
Solution Approach 1:
The engine is segmented into two independent fan stages with separate control systems. The first fan stage maintains stable operation and provides the core drive, while the second fan stage is controlled independently through the transmission system to adjust bypass flow and improve transient response without significantly affecting the overall spool speed stability.
Data Source
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AI summary
One embodiment of the present invention is a unique gas turbine engine. Another embodiment is a unique variable cycle gas turbine engine. Another embodiment is a unique adaptive fan system for a variable cycle turbofan engine having at least one turbine. Another embodiment is a unique method for operating a variable cycle gas turbine engine. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines and related systems.