Aircraft Propulsor Mounting for Noise Shielding
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Solution Overview
Problem
Open fan propulsors in aircraft produce high noise levels, which are undesirable and violate stringent noise regulations, while noise-reducing technologies often compromise fuel efficiency and aerodynamics.
Innovation Solution
The aircraft configuration includes a fuselage and wing with propulsors mounted such that rotors are located longitudinally between the rear spar and wing trailing edge, with a lowest point of the rotor diameter above the wing upper surface, utilizing the wing's upward curvature under 1-g wing loading to provide acoustic shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If open fan propulsors are used to improve fuel efficiency, then fuel efficiency is improved, but noise output increases to unacceptable levels
Solution Approach 1:
The wing structure serves as an intermediary element that naturally shields the propulsor noise from ground-level observers. The upward curvature of the wing under 1-g loading creates a geometric barrier between the noise source (propulsor) and the measurement points, allowing the open fan propulsor to maintain its fuel efficiency benefits while reducing noise impact on communities.
2Object-generated harmful factors
If noise-reducing technologies such as increased rotor spacing or blade cropping are applied, then noise levels are reduced, but thrust and fuel efficiency decrease
Solution Approach 1:
The invention converts the harmful noise radiation pattern of the open fan propulsor into a beneficial outcome by utilizing the wing's upward curvature to redirect noise away from ground-level areas. This approach achieves noise reduction without modifying the propulsor configuration, thereby preserving thrust and fuel efficiency.
3Object-generated harmful factors
If non-aerodynamic surfaces are introduced or existing aerodynamic surfaces are increased for noise blockage, then noise is reduced, but aerodynamic performance is compromised
Solution Approach 1:
The wing serves multiple functions: it provides aerodynamic lift for flight and simultaneously acts as a noise shield for the propulsor. By positioning the propulsor such that the wing's upward curvature under 1-g loading blocks noise radiation, the same aerodynamic surface performs dual roles without requiring additional non-aerodynamic structures.
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
This configuration effectively attenuates noise emissions by up to 15 dB without compromising fuel efficiency or introducing non-aerodynamic surfaces, meeting noise regulations while maintaining aerodynamic performance.
Implementation Method 1
utilizing the wing's upward curvature under 1-g wing loading to provide acoustic shielding
Data Source
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AI summary
An arrangement for an aircraft includes a fuselage, a wing, and a propulsor. The wing may have a wing upper surface, a rear spar and a wing trailing edge. The propulsor may include at least one rotor having a rotor diameter and a rotor axis. The propulsor may be mounted such that the rotor is located longitudinally between the rear spar and the wing trailing edge. The propulsor may also be mounted such that a lowest point of the rotor diameter is located vertically above the wing upper surface.