Noise Attenuation Panel With Interconnected Cells For Low Frequency Noise
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Solution Overview
Problem
Existing noise attenuation panels in gas turbine engines, particularly those with a honeycomb structure, are ineffective in reducing low-frequency noise due to their resonance frequency limitations, which require a small neck diameter and large body volume, making them bulky and unsuitable for space-constrained areas.
Innovation Solution
The noise attenuation panel interconnects cells via communication holes, with one cell preventing gas flow, allowing the panel to function as a series of Helmholtz resonators with a lowered resonance frequency, enabling a thinner design suitable for space-constrained areas like guide vanes, by optimizing the distance between the inlet hole and the end cell and using a honeycomb structure for structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional Helmholtz resonator design is used with small neck diameter and large body volume to achieve low frequency noise attenuation, then the resonance frequency is lowered, but the panel depth becomes large and unsuitable for space-constrained areas
Solution Approach 1:
The panel is divided into multiple cells arranged in series between the first and second walls, with partition walls creating separate compartments. This segmentation allows the acoustic treatment to be distributed across multiple smaller units rather than requiring a single large-depth cavity, thereby reducing the overall panel depth while maintaining low-frequency noise attenuation effectiveness.
Solution Approach 2:
Multiple cells are nested in series between the first and second walls, with each cell containing a portion of the acoustic treatment function. The cells are arranged such that they occupy space more efficiently than a single large cavity, nesting the acoustic function within a compact depth profile that fits space-constrained areas like guide vanes.
2Adaptability or versatility
If the panel depth is reduced to fit space-constrained areas, then the panel becomes suitable for positions like guide vanes, but the low frequency noise attenuation capability is compromised
Solution Approach 1:
The acoustic treatment function is segmented into multiple cells that can be arranged in series within the available space. This allows the panel to adapt to different depth constraints in various engine positions while maintaining the cumulative acoustic treatment effect needed for low-frequency noise attenuation.
Solution Approach 2:
Instead of relying solely on increasing depth in one dimension to achieve low-frequency attenuation, the invention uses multiple cells arranged in series between the walls, effectively utilizing the surface area and cellular arrangement to achieve the acoustic effect within reduced depth, thereby enabling adaptation to various engine positions with different spatial constraints.
3Adaptability or versatility
If more through holes are added to increase gas flow, then the noise attenuation panel can treat more positions, but the structural stability of the honeycomb pattern is reduced
Solution Approach 1:
Through holes are selectively provided only in the first wall rather than distributed across all walls and partition walls. This local placement allows gas flow and noise attenuation functionality while preserving the structural integrity of the honeycomb pattern in the second wall and partition walls, maintaining structural stability while enabling adaptability to multiple engine positions.
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 design effectively attenuates low-frequency noise with a minimal depth requirement, allowing for the panel's use in more positions within the engine, including guide vanes, while maintaining structural stability under pressure conditions.
Implementation Method 1
the cells of the honeycomb material act as a Helmholtz resonator when they communicate with the outside. This provides an acoustic panel which absorbs the noise over a certain range of frequencies
Implementation Method 2
viscous forces in the neck (through hole) together with nonlinear effects serves as the damping
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
The invention relates to a noise attenuation panel (20,21,22) comprising a first wall (31), a second wall (32) and partition walls (33,34) connected to the first and second walls (31,32) and defining cells (35,36,37) between the first and second walls (31,32), wherein the first wall (31) is provided with a plurality of through holes (40). At least two of said cells (35,36,37) are interconnected via a communication hole (38,39). One of said through holes (40) leads to a first (35) of said at least two interconnected cells and a second (37) of said interconnected cells is configured to prevent any gas flow through the second cell.