Front Fan Separation Wall Serrations for Broadband Noise Reduction
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Solution Overview
Problem
In Ultra-High Bypass Ratio turbofan engines, the interaction between the fan wake and stator vanes generates dominant broadband noise, necessitating new solutions to maintain and reduce noise levels, particularly due to the short axial distance between the fan and inlet guide vanes, leading to higher air turbulence exposure.
Innovation Solution
The introduction of an annular separation wall with a serrated leading edge, featuring a profile with undulations that optimize geometry to minimize noise correlation, using criteria such as amplitude, spacing, and alignment relative to fan blades, to reduce noise radiation from the interaction between the fan wake and stator vanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the axial distance between the fan and inlet guide vanes is reduced to decrease nacelle length, then the nacelle length is reduced, but the noise level increases due to higher air turbulence exposure
Solution Approach 1:
The leading edge of the annular separation wall is given a serrated profile with specific geometric characteristics (amplitude, wavelength, orientation) that differ from the rest of the structure. This localized modification targets the specific region where fan wake interacts with the separation wall, reducing broadband noise generation at this critical location while maintaining the overall compact nacelle design
Solution Approach 2:
Instead of modifying the axial spacing between components, the invention addresses noise reduction by introducing a new dimensional characteristic - the serrated profile with specific amplitude and wavelength parameters. This transforms the problem from a one-dimensional spacing issue to a multi-dimensional geometric optimization, allowing noise control without increasing nacelle length
2Adaptability or versatility
If the fan diameter is increased to achieve higher bypass ratio, then the bypass ratio is improved, but the interaction noise with stator vanes increases
Solution Approach 1:
The serrated leading edge of the annular separation wall provides localized noise reduction at the critical interaction zone between fan wake and stator vanes. This allows the system to maintain large fan diameter for high bypass ratio while suppressing the harmful interaction noise through targeted geometric modification at the separation wall
Solution Approach 2:
The serrated profile introduces asymmetry in the leading edge geometry of the annular separation wall, with teeth and hollows creating an non-uniform structure that disrupts the coherent interaction between fan wake and stator vanes, thereby reducing broadband noise generation
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
The serrated leading edge design effectively reduces noise radiation by minimizing the correlation between noise sources and turbulent flow areas, enhancing noise reduction and robustness while maintaining efficient airflow guidance.
Implementation Method 1
the interaction of the fan wake with the IGVs, OGVs and slat is one of the dominant broadband noise sources
Implementation Method 2
the leading edge of the beak of said annular separation wall has a profile with serrations having a succession of teeth and hollows
Data Source
Figure 1~8
Figure 9~11
Figure 12~13
AI summary
This relates to a turbomachine with a front-mounted fan, comprising an annular flow-splitting wall (160) provided a nose (16), for splitting an incoming air flow between a primary flow and a secondary flow, the nose having a leading edge; guide vanes IGV for guiding the primary flow, and guide vanes OGV for guiding the secondary flow. The leading edge of the nose (16) has a serrated profile (28) exhibiting a succession of teeth and of troughs.