Variable Tip Gap Control for Ducted Aircraft Propellers
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Solution Overview
Problem
Current ducted rotor systems lack the ability to effectively monitor and control the changing tip gap between rotor blades and the duct, leading to performance degradation and increased risk of collisions, as they cannot adjust to deformations caused by flight conditions and external factors like bird strikes.
Innovation Solution
A tip gap monitoring and control system that includes sensors to detect changes in the tip gap and actively or semi-actively adjusts the position of blade tips or inner duct surfaces to maintain an optimal distance, using mechanisms like pitch-span converters, tension-torsion straps, and sacrificial blade tips to ensure safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor blades are shortened to prevent collisions with the duct, then the risk of collision is reduced, but the thrust production efficiency deteriorates
Solution Approach 1:
The patent implements variable blade length through extendable blade tip extensions that can dynamically adjust between retracted and extended positions. This allows the rotor blade length to change based on flight conditions, enabling the system to maintain optimal thrust efficiency when collisions are not a risk while extending collision protection when needed, thus resolving the contradiction between collision risk reduction and thrust production efficiency
Solution Approach 2:
The patent changes the physical parameter of blade length by deploying blade tip extensions that extend beyond the main blade body when collisions are anticipated and retract when safe. This parameter change allows the system to optimize both safety and performance by adjusting blade length rather than maintaining a fixed conservative length, thereby resolving the contradiction between reliability and productivity
2Productivity
If the tip gap is reduced to maximize duct performance, then the thrust efficiency is improved, but the risk of blade-duct collision increases
Solution Approach 1:
The patent implements dynamic tip gap control through blade tip extensions that can extend or retract based on real-time collision risk assessment. This allows the system to maintain small tip gaps for optimal thrust efficiency when safe, and increase the tip gap by extending blade tips when collision risk is detected, thereby resolving the contradiction between thrust efficiency and collision risk
Solution Approach 2:
The patent employs a control system that monitors flight conditions and collision risk, providing feedback to adjust blade tip extension position. This feedback mechanism enables the system to continuously optimize the tip gap based on current operational status, maintaining high thrust efficiency while preventing blade-duct collisions by adjusting the gap dynamically rather than using a fixed conservative setting
3Productivity
If the rotor blades are made longer to improve thrust efficiency, then the productivity increases, but the likelihood of collision with the duct increases
Solution Approach 1:
The patent segments the rotor blade into a main blade body and an extendable blade tip extension. This segmentation allows the main blade to maintain optimal length for thrust efficiency while the separate extension component can be deployed or retracted based on collision risk, thus resolving the contradiction by separating the thrust-generating function from the collision-risk function
Solution Approach 2:
The patent makes the blade tip extension dynamic rather than fixed, allowing it to extend when collisions are anticipated and retract when safe. This dynamic capability enables the system to maintain long blade lengths for high thrust efficiency during safe operations while providing collision protection when needed, resolving the contradiction between productivity and reliability
Data Source
AI summary
A proprotor system for a ducted aircraft includes a duct and proprotor blades surrounded by the duct. Each proprotor blade is rotatable about a respective pitch change axis. The proprotor blades are configured to change collective pitch about the pitch change axes. The proprotor blades are extendable along the pitch change axes into various positions including a retracted position and an extended position. The proprotor blades change between the retracted position and the extended position based on the collective pitch of the proprotor blades, thereby controlling a tip gap between the proprotor blades and the duct.