Rotor assembly
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Solution Overview
Problem
Ducted fan systems face limitations in thrust generation due to unfavorable flow characteristics caused by air mixing between fan blades and the duct, and the rigidity of ducted rotors is compromised by external control structures, which can lead to reduced efficiency and stability.
Innovation Solution
A rotor assembly with a control tube and crosshead mechanism that allows for mechanical control of rotor blade pitch, using a trunnion assembly to translate the control tube and crosshead, enabling rotation of rotor blades about their pitch-change axes without the need for external pitch links, thereby maintaining rotor hub stiffness and minimizing tip gap for improved thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tip gap is minimized to maximize thrust, then thrust generation is improved, but the risk of catastrophic fan movement increases due to reduced flexibility
Solution Approach 1:
The rotor hub assembly incorporates flexible elements that allow controlled movement and flexion of the fan assembly. This dynamic capability enables the system to maintain minimal tip gaps for optimal thrust generation while simultaneously accommodating movement forces to prevent catastrophic contact between fan blades and the duct.
2Ease of operation
If additional structure is added to the rotor blade control mechanism, then pitch control capability is improved, but the stiffness of the rotor hub assembly is reduced
Solution Approach 1:
The control tube is nested within the rotor hub assembly, with the crosshead mechanism positioned inside the hub. This nested arrangement allows pitch control functionality to be integrated within the existing hub structure, providing full pitch control capability without requiring external additions that would compromise hub stiffness.
Solution Approach 2:
The control tube extends axially through the rotor hub, utilizing the axial dimension for control mechanisms rather than requiring radial or lateral extensions. This dimensional approach allows pitch control structure to be positioned along the rotation axis, maintaining rotor hub stiffness in critical radial directions while enabling full pitch control functionality.
Data Source
AI summary
A rotor assembly including a rotor mast, a rotor hub coupled to the rotor mast, a plurality of rotor blades coupled to the rotor hub, a control tube extending through the rotor mast, a crosshead coupled to the control tube, and a mechanism configured to drive the rotor mast in rotation. Wherein the mechanism is longitudinally positioned between a top portion and a bottom portion of the control tube and translation of the control tube relative to the rotor mast causes rotation of the rotor blades about their pitch-change axes. While the crosshead is installed, the crosshead is prevented from angular rotation about the mast axis. A pin of a rotor blade assembly is captured between opposing tabs of the crosshead and movable relative to the opposing tabs in response to translation of the crosshead along the mast axis.