Adaptive Vertical Lift Engine Fan Variable Pressure Control
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Solution Overview
Problem
Current turbofan engines face limitations in maintaining constant operating pressure ratios and flexibility in load shifting between shaft and fan loading, leading to inefficient performance at diverse flight conditions and varying power settings, due to fundamental operating characteristics that result in bypass/core pressure leakage.
Innovation Solution
The implementation of an adjustable inlet guide vane and a partial midspan shroud that separates the core and bypass fluid paths, with a seal to restrict flow migration, allowing for variable pressure control and reduced leakage, enabling efficient operation across a wide range of flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional turbofan engine configuration is used with fixed fan pressure ratio and bypass ratio, then the engine can be designed to a reasonable size for combat maneuvers, but the engine performance suffers from bypass/core pressure leakage at reduced fan power settings and cannot operate efficiently at low speed flight conditions
Solution Approach 1:
The patent applies dynamics by making the fan pressure ratio variable through an adjustable fan blade pitch mechanism. The fan blades can be adjusted between different pitch angles to change the fan pressure ratio dynamically, allowing the engine to adapt to different flight conditions (low-speed flight, high-speed flight, combat maneuvers) without fixed compromises. This dynamic adjustment eliminates bypass/core pressure leakage by optimizing the pressure ratio at each operating condition.
Solution Approach 2:
The patent changes the operating parameters of the engine by variable fan pressure ratio adjustment. By changing the fan blade pitch angle, the fan pressure ratio is varied to match different flight requirements. This parameter change allows the engine to maintain optimal performance across diverse conditions rather than being locked into a single fixed pressure ratio that causes energy loss through pressure leakage.
2Power
If the fan pressure ratio is optimized for combat maneuvers, then thrust production is sufficient for high-speed and maneuvering flight, but the engine cannot efficiently transmit power to the shaft for low speed flight
Solution Approach 1:
The adjustable fan blade pitch mechanism allows the fan to dynamically adjust its characteristics. At high-power settings for combat maneuvers, the fan operates at a higher pressure ratio optimized for thrust production. At low-speed flight conditions, the fan blade pitch is adjusted to a lower angle, reducing the fan pressure ratio and allowing more power to be transmitted to the shaft through the core flow, thereby improving versatility across different power transmission modes.
3Productivity
If the bypass ratio is increased to improve low-speed flight efficiency, then more air flows through the bypass stream, but the engine size increases and performance at high-speed combat maneuvers deteriorates
Solution Approach 1:
Instead of using a fixed high bypass ratio that increases engine size, the patent uses a variable fan pressure ratio system. The bypass ratio effect is achieved dynamically by adjusting fan blade pitch rather than statically through geometry. This allows the engine to maintain a compact size while achieving high bypass ratio benefits at low speeds through active control of the fan pressure ratio, improving low-speed efficiency without the penalty of increased engine dimensions.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A turbofan engine (10) has a fan (42) in fluid communication with a core stream (28) and a bypass stream (30) of air separated by splitters disposed both upstream and downstream (24, 25) of the fan (42). A blade splitter (shroud) (26) on the fan (42) partially spans a fan blade (42) thus separating the core and bypass streams (28, 30) downstream while leaving a communication gap (55) upstream for communication between the flows (28, 30). The communication gap (55) expands an operational range of the fan (42) over fans without the communication gap (55).