Propeller Blade Groups with Varying Geometric Characteristics for Noise Reduction
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Solution Overview
Problem
Existing propeller-driven aircrafts continue to face challenges in reducing noise levels, both inside the fuselage and in the surrounding environment, due to the persistent nature of propeller noise, which affects passenger comfort and community annoyance despite previous noise reduction methods.
Innovation Solution
The propeller design incorporates multiple blade groups with varying geometric characteristics such as chord, twist, length, blade angle, and camber, resulting in distinct noise signatures that distribute energy over a broader frequency range, reducing both near-field and far-field noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional propeller designs with uniform blades are used, then manufacturing is simple and reliable, but noise levels remain high both inside and outside the aircraft
Solution Approach 1:
The patent applies local quality by giving each blade a unique geometric configuration (different chord lengths, twist angles, airfoil sections) at specific radial positions along the blade span, while maintaining uniform geometry in other aspects. This localized differentiation of blade characteristics creates varied noise signatures from each blade, effectively reducing overall propeller noise without requiring complete redesign of the entire propeller system.
Solution Approach 2:
The patent employs asymmetry by deliberately designing blades with non-uniform geometric characteristics across the blade set. Each blade possesses asymmetric features relative to others, such as varying camber distributions or twist profiles, which cause each blade to generate distinct aerodynamic noise characteristics. This asymmetric design breaks the periodicity of noise generation, distributing energy across a broader frequency spectrum and reducing peak noise levels.
2Object-affected harmful factors
If swept blade propellers or increased blade count are used, then noise reduction is achieved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies parameter changes by systematically varying geometric parameters (chord length, twist angle, airfoil section thickness, camber) across different blades and along the blade span. These controlled parameter variations are implemented within existing manufacturing capabilities, using standard blade fabrication processes rather than requiring new manufacturing technologies. The changes are achieved through adjusted molding or forming parameters during production.
Data Source
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AI summary
A propeller (32) is provided including a hub (36) and a first blade group (50a) and a second blade group (50b). The first blade group (50a) includes at least one first propeller blade (40a) and the second blade group (50b) includes at least one second propeller blade (40b). The at least one first propeller blade (40a) and the at least one second propeller blade (40b) are mounted to and equidistantly spaced about the hub (36). The at least one first propeller blade (40a) of the first blade group (50a) has at least one geometric characteristic different from the at least one second propeller blade (40b) of the second blade group (50b). The different blade groups (50a-50d) will generate different noise signatures over a wider range of frequencies allowing for the design of low noise propeller systems.