Variable Cycle Gas Turbine Propulsor
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Solution Overview
Problem
Conventional gas turbine engines are inefficient at both subsonic and supersonic speeds due to their design, which limits their operational efficiency over a wide range of speeds.
Innovation Solution
A variable cycle gas turbine propulsion system incorporating a turbofan engine, peripheral duct, annular frame, auxiliary turbine, and auxiliary fan, which allows for adjustable airflow to optimize thrust production across different speed modes by altering the bypass ratio and fan pressure ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional turbojet engine design is used, then high exhaust velocity is achieved for supersonic speed efficiency, but propulsive efficiency deteriorates at subsonic speeds
Solution Approach 1:
The patent applies dynamics by making the bypass ratio variable through movable ducts and flow control mechanisms. The bypass ratio can be adjusted dynamically: at subsonic speeds, a high bypass ratio is used to improve propulsive efficiency by accelerating large masses of air to lower velocities; at supersonic speeds, the bypass ratio is reduced to allow higher exhaust velocities for better performance. This dynamic adjustment resolves the contradiction between maintaining high exhaust velocity and achieving good propulsive efficiency across different flight regimes.
2Use of energy by moving object
If a high bypass ratio is used, then propulsive efficiency is improved at subsonic speeds, but acceleration and response deteriorate at supersonic speeds
Solution Approach 1:
The variable cycle engine uses dynamic flow control mechanisms including movable bypass ducts, adjustable flow diverters, and variable area nozzles that can rapidly change the bypass ratio. During acceleration phases or supersonic flight, the system dynamically reduces the bypass ratio to increase exhaust velocity and improve acceleration response. During steady subsonic cruise, the bypass ratio is increased to maximize propulsive efficiency. This dynamic adaptability resolves the contradiction between propulsive efficiency and acceleration performance.
3Device complexity
If a fixed cycle design is used, then device complexity is minimized, but adaptability to different speed conditions deteriorates
Solution Approach 1:
The patent implements a variable cycle engine with dynamic flow control systems including movable bypass ducts, adjustable flow diverters, and variable area nozzles that can change the engine's operational characteristics in real-time. These dynamic components allow the engine to adapt its bypass ratio and flow paths to optimize performance across different flight regimes from subsonic to supersonic speeds, significantly improving adaptability while accepting the trade-off of increased device complexity.
Solution Approach 2:
The variable cycle engine design incorporates multi-functional components that can operate in different modes. The bypass system, flow diverters, and nozzle assemblies serve multiple functions: they control bypass ratio for efficiency, manage flow distribution for acceleration, and adapt to different flight regimes. This multi-functionality allows a single engine design to replace what would traditionally require different engine types for different speed regimes, improving versatility while managing complexity through integrated design.
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 system achieves improved propulsive efficiency at both subsonic and supersonic speeds by optimizing airflow distribution and pressure ratios, enhancing fuel economy and reducing noise in subsonic operations while improving acceleration and response in supersonic conditions.
Implementation Method 1
The auxiliary turbine is connected to an aft end of the core engine and is configured to receive the combustion air
Implementation Method 2
The auxiliary fan is connected to the auxiliary turbine and is configured to receive airflow from the peripheral duct
Implementation Method 3
The propulsive gas flow is exhausted at a downstream or rear end of the engine through an exhaust nozzle, after flowing axially through the engine. The exhaust gas exits the nozzle at a higher velocity than the velocity of the inlet air thereby producing thrust with the net acceleration of the flow
Data Source
AI summary
A gas turbine propulsion system comprises a turbofan engine, a peripheral duct, an annular frame, an auxiliary turbine and an auxiliary fan. The turbofan engine is configured to produce bypass air and combustion air. The bypass air flows through a bypass duct and the combustion air flows through a core engine. The peripheral duct surrounds the turbofan engine and is configured to selectively receive peripheral inlet air. The annular frame is disposed aft of the bypass duct and the peripheral duct, and is rotatable to alternately guide the bypass air out the bypass duct or the peripheral duct. The auxiliary turbine is connected to an aft end of the core engine and is configured to receive the combustion air. The auxiliary fan is connected to the auxiliary turbine and is configured to receive airflow from the peripheral duct.