Flow Control Ducted Fans Aperture Design
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Solution Overview
Problem
Ducted fan systems in aircraft are prone to flow separation and fan inlet distortion during high-angle-of-attack or crosswind conditions, leading to compromised performance, especially in tilt-wing aircraft where efficient inlet designs are limited across different flight modes.
Innovation Solution
A flow control apparatus with a duct featuring a controllable aperture on its exterior surface, upstream of the fan, which can be partially opened to create a secondary flow path into the duct, reducing flow separation and improving fan performance by adapting to various flight modes and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed inlet design is used for ducted fans, then the structure is simple, but fan performance is compromised in high angle of attack or crosswind conditions due to flow separation and inlet distortion
Solution Approach 1:
The inlet design incorporates movable doors that can change position based on flight conditions. The doors are actuated to open or close specific aperture groups depending on whether the aircraft is in hover, transition, or forward flight mode, allowing the inlet geometry to dynamically adapt rather than remain fixed.
Solution Approach 2:
The system changes the effective inlet geometry parameters by selectively opening or closing different aperture groups. This alters the flow path characteristics and inlet distortion patterns to match different flight regimes, improving fan performance across the full operating envelope.
2Reliability
If active flow control devices such as fluidic oscillators are used to improve flow over ducted fans, then flow attachment is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts the flow control function from complex active devices and implements it through passive geometric modifications to the inlet structure. The controllable apertures and doors provide flow management capabilities without requiring fluidic oscillators, pulsating jets, or other active flow control mechanisms.
3Productivity
If the controllable aperture is opened to create a secondary flow path, then flow separation is reduced and fan efficiency is improved, but device complexity increases
Solution Approach 1:
The inlet structure is segmented into multiple aperture groups that can be independently controlled. Each group can be opened or closed based on specific flight conditions, allowing granular control over the secondary flow path rather than a single all-or-nothing aperture.
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 controllable aperture system enhances fan efficiency and reduces power consumption by maintaining flow attachment and adapting to different flight conditions, such as hover and cruise modes, thereby improving overall aircraft performance.
Implementation Method 1
ducted fans can be prone to issues including flow separation and fan inlet distortion in certain conditions
Data Source
AI summary
Flow control ducted fans are disclosed. A disclosed example flow control apparatus for use with an aircraft includes a duct defining an inner cavity with a primary flow path, a fan disposed in the inner cavity, an aperture on an exterior surface of the duct and upstream from the fan, the aperture fluidly coupled to the inner cavity to define a secondary flow path, and a door to control a degree to which the aperture is opened.