Shrouded Rotor Acoustic Reflector Layout for Ground Noise Redirection
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Solution Overview
Problem
Existing shrouded rotor systems in aircraft, such as ducted yaw control systems, emit noise in all directions, particularly towards the ground, causing disturbance to individuals on the ground.
Innovation Solution
Incorporation of acoustic reflectors positioned transversely to the air stream, with acoustically reflective sections that reflect acoustic waves away from the ground, utilizing convex shapes visible from the ground and concave shapes from above, to redirect noise upwards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If acoustic reflectors are added to redirect noise away from the ground, then noise emission towards the ground is reduced, but device complexity increases
Solution Approach 1:
The acoustic reflector is merged with the existing duct structure of the shrouded rotor system. The reflector forms an integral part of the duct, eliminating the need for separate noise control components while achieving noise redirection functionality.
Solution Approach 2:
The duct structure serves multiple functions: it contains the rotor blades, directs airflow, and simultaneously acts as an acoustic reflector to redirect noise away from the ground. This multi-functionality reduces overall device complexity by combining noise control with existing structural elements.
2Object-affected harmful factors
If acoustic reflectors are positioned transversely to the air stream, then noise reflection away from ground is achieved, but manufacturing complexity increases
Solution Approach 1:
The acoustic reflector incorporates curved surfaces with specific geometric profiles that are optimized for acoustic reflection. These curved geometries are designed to efficiently redirect acoustic waves away from the ground while being manufacturable using standard aerospace forming techniques.
Solution Approach 2:
The reflector geometry is designed with specific dimensional parameters and angular orientations that optimize acoustic reflection. By carefully selecting and adjusting these geometric parameters, the design achieves effective noise control while remaining compatible with existing manufacturing capabilities.
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
Significantly reduces noise emission towards the ground by reflecting acoustic waves away from individuals on the ground, achieving noise attenuation of several decibels.
Implementation Method 1
the acoustic reflector comprising an acoustically reflective section situated transversely to the air stream to reflect acoustic waves exiting the air stream towards the ground in a direction away from the ground
Data Source
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AI summary
The present invention relates to an aircraft (1) equipped with a shrouded rotor system (20), said system (20) comprising a shroud (21) and a rotor (31) equipped with blades (32), the blades (32) being arranged in an air stream (40) delimited by the shroud (21) and movable in rotation about an axis of rotation (AXROT) of the rotor (31), the shroud (21) extending longitudinally in a rear direction (AR) from a structure (2), the shroud (21) extending in an upward direction from a bottom (211) to a top (212) and transversely from a first side (213) to a second side (214). Said aircraft (1) includes at least one acoustic reflector (51) reflecting in a direction away from the ground (100) acoustic waves (95) exiting the air stream (40) as they move towards the ground (100).