Gas Turbine Nacelle Low-Frequency Sound Damping
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Solution Overview
Problem
Existing aircraft gas turbine engine casings with honeycomb structure layers for noise damping are limited in installation space and ineffective for low-frequency sound damping, requiring multiple parts and structural modifications.
Innovation Solution
Additional sound-damping elements are integrated radially outside the honeycomb structure layer, extending axially and circumferentially to form a larger damping unit, connected via recesses to create a labyrinthine soundproofing system, allowing for effective low-frequency noise absorption without dividing the honeycomb structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the honeycomb structure layer is divided into multiple parts for assembly, then the installation space is reduced, but the low-frequency sound damping effectiveness is lost
Solution Approach 1:
The sound damping system is segmented into two functional parts: a honeycomb structure layer for high-frequency damping and additional sound-damping elements for low-frequency damping. These parts are assembled together to form a complete damping system that fits within the engine housing while maintaining effectiveness across the full frequency spectrum.
Solution Approach 2:
The additional sound-damping elements extend in the axial direction beyond the honeycomb structure layer, utilizing the axial dimension to accommodate low-frequency damping components without compromising the radial space available for high-frequency damping. This dimensional extension allows both damping mechanisms to coexist effectively.
2Reliability
If the fan housing flange diameter is increased to accommodate sound-damping elements, then low-frequency sound damping is improved, but the structural complexity increases
Solution Approach 1:
The fan housing flange is designed to serve multiple functions: it provides the structural connection between engine components and simultaneously accommodates the additional sound-damping elements. This multi-functionality allows low-frequency damping to be integrated without requiring separate structural modifications.
Solution Approach 2:
The sound-damping elements are merged with the fan housing structure, where the housing itself serves as part of the sound damping system. This integration reduces the need for separate structural components and simplifies the overall assembly.
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 enhances low-frequency sound damping, optimizes installation space, and allows for easy integration into existing engine housings, improving fan performance and load distribution while maintaining a lightweight and cost-effective design.
Implementation Method 1
The honeycombs of the honeycomb structure layer, which consists for example of metal or a composite material, form λ/4 dampers
Implementation Method 2
Each sound-damping element has at least one hollow chamber which extends essentially in the axial direction and is connected to the honeycomb structure layer via recesses. The hollow chamber thus serves to dampen low-frequency vibrations
Data Source
Figure 1
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AI summary
The housing (29) has a honeycomb structural layer arranged in a region of an inflow-side air inlet (11) at the housing arranged upstream of a fan (12). Sound proofing elements arranged at radially outside the honeycomb structural layer that extends in axial direction. The sound damping elements are arranged annularly adjacent to one another in circumferential direction. Each sound-damping element comprises a hollow chamber extending in axial direction through recesses in communication with the honeycomb structural layer.