Variable Geometry Inlet for Ducted Fan Using Stretchable Skin
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Solution Overview
Problem
Ducted fans with fixed geometry inlets face challenges in accommodating conflicting performance requirements for distinct operational modes, such as hover and high-speed cruise, leading to mechanical and control complexity, reduced reliability, and increased costs.
Innovation Solution
A variable geometry inlet system featuring a retractable ring, a pressurizable tube, and a stretchable skin that transitions between modes, allowing the leading edge to change configuration between operational modes to optimize performance, with the retractable ring extending axially in one mode and retracting in another, and the tube inflating or deflating to adjust the inlet geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed geometry inlet is selected to facilitate enhanced performance for an expected operational mode, then performance in that mode is improved, but performance in other operational modes deteriorates
Solution Approach 1:
The inlet geometry is made dynamically adjustable through a variable geometry mechanism that can change the inlet shape between at least two different configurations. This allows the ducted fan to optimize performance for different operational modes (e.g., hover and high-speed cruise) by selecting the appropriate inlet geometry, thereby resolving the contradiction between fixed-geometry performance and multi-mode adaptability.
2Adaptability or versatility
If a variable geometry inlet is provided to vary between first and second geometries for different operational modes, then adaptability is improved, but mechanical and control complexity increases
Solution Approach 1:
The patent replaces complex mechanical variable geometry systems with a simpler alternative where the inlet geometry is defined by the interaction between a stretchable skin and either a retractable ring or inflated tube. This substitution reduces mechanical complexity and control requirements while maintaining the ability to vary inlet geometry between different operational modes.
Solution Approach 2:
The inlet incorporates a stretchable skin that can elastically deform to define different inlet geometries. This flexible membrane approach eliminates the need for complex rigid mechanical adjustment mechanisms, thereby reducing device complexity while enabling variable geometry functionality for different operational modes.
3Adaptability or versatility
If mechanical variable geometry systems are used to adjust inlet geometry, then geometry variation capability is improved, but reliability decreases
Solution Approach 1:
The use of a stretchable skin as the primary geometry-defining element eliminates moving mechanical joints, bearings, and complex actuation systems that are prone to failure. The elastic deformation of the skin provides a inherently more reliable method of geometry variation compared to traditional mechanical systems with multiple moving parts.
Solution Approach 2:
The patent employs an inflatable tube as an alternative to mechanical adjustment systems. By using pneumatic pressure to inflate or deflate the tube, the inlet geometry can be varied without mechanical moving parts, thereby improving reliability while maintaining geometry variation capability for different operational modes.
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 enhances performance in both operational modes while reducing mechanical and control complexity, improving reliability and cost-effectiveness by maintaining desired aerodynamic shapes through elastic deformation and pressure adjustments.
Implementation Method 1
The stretchable skin is elastically deformable in at least a circumferential direction about a longitudinal axis of the ducted fan
Implementation Method 2
The tube is pressurizable to a relatively deflated state in the first mode and to a relatively inflated state in the second mode
Data Source
AI summary
A variable geometry inlet for a ducted fan is selectively transitionable between a first and second mode. The inlet includes a retractable ring that extends circumferentially about the inlet and is selectively movable between an axially extended position in the first mode and an axially retracted position in the second mode. A tube extends circumferentially proximate the retractable ring, and is pressurizable to a relatively deflated state in the first mode and to a relatively inflated state in the second mode. A stretchable skin extends circumferentially proximate the retractable ring, and is elastically deformable in at least a circumferential direction about a longitudinal axis of the fan. A leading edge of the inlet in the first mode is defined by the stretchable skin disposed against a forward edge of the retractable ring, and in the second mode by the stretchable skin disposed against at least a portion of the tube.