Variable Pitch Rotor With Tensioning Joint Mechanism
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Solution Overview
Problem
Aerodynamic rotors in aircraft experience reduced stiffness due to large diameter fan blades, leading to noise generation and efficiency loss from small deformations, particularly in turbofan engines with variable pitch blades, which are exacerbated by flexible structures and distorted airflow.
Innovation Solution
A structure with tensioning joint mechanisms and tension elements that maintain constant lateral force along the blade span, allowing pitch variation without altering tension, thereby increasing stiffness and reducing noise through acoustic node modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fan diameter is increased to improve fuel efficiency, then propulsive performance is improved, but blade stiffness is reduced leading to increased noise and deformation
Solution Approach 1:
The blade structure is segmented into multiple functional zones: the variable pitch mechanism at the root, the tension element attachment points at intermediate stations, and the aerodynamic profile at the tip. This segmentation allows independent optimization of each zone - the root for pitch control, the intermediate stations for stiffness reinforcement, and the tip for aerodynamic performance.
Solution Approach 2:
The rotor system employs composite construction combining traditional blade materials with tension element reinforcement. The tension elements act as structural reinforcements that can be integrated with the existing blade composite structure, creating a hybrid system that maintains flexibility where needed while adding stiffness where required.
2Adaptability or versatility
If blade pitch is varied to optimize performance at different flight phases, then adaptability is improved, but structural stability is compromised due to reduced stiffness
Solution Approach 1:
The system dynamically adjusts blade pitch angle according to flight conditions while the tension elements provide continuous structural support. The variable pitch mechanism remains fully functional, but the tension elements ensure that during pitch transitions and at various pitch settings, the blade maintains adequate stiffness to prevent excessive deformation and maintain structural stability.
3Object-generated harmful factors
If tension elements are added to increase blade stiffness, then noise is reduced, but device complexity increases
Solution Approach 1:
The tension elements serve multiple functions simultaneously: they act as structural reinforcements to increase blade stiffness, provide aerodynamic benefits by reducing deformation-induced noise, and maintain compatibility with the variable pitch mechanism. This multi-functionality reduces the need for separate components and simplifies the overall system architecture.
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 solution effectively reduces noise and enhances propulsive performance by increasing blade stiffness and shifting natural frequencies away from blade passage frequencies, improving aerodynamic and acoustic properties.
Implementation Method 1
at least one tension element engaged by the at least one tension joint mechanism in each blade, said at least one tension element configured to maintain tension between the blades in the rotor
Implementation Method 2
exerting a lateral correcting force on the blades with the at least one tension element to establish acoustic nodes to modulate deformation wavelength of the blades
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A propulsion unit having reduced noise employs a rotor (16a, 16b) having a plurality of variable pitch blades (22). A tensioning joint mechanism (28) is carried within each blade (22) and a tension element (20) is engaged by the tension joint mechanism (28). The tension element (20) is configured to maintain tension between the blades (22) in the rotor (16a, 16b) and the tensioning joint mechanism (28) adapted to allow variation of pitch of the blades (22) without altering tension in the tension element (20).