Turbofan Airfoil Protrusions for Noise Reduction
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Solution Overview
Problem
Turbofan engines generate significant noise due to trailing-edge self-noise and wake interaction noise, which are not effectively mitigated by existing airfoil designs.
Innovation Solution
The airfoil features protrusions with curvilinear shapes along the pressure and suction sidewalls downstream from the mid-point of the chord line and upstream of the trailing edge, promoting wake mixing and reducing interaction noise through streamwise vortical mixing, optimized for local boundary layer conditions and aerodynamic pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional airfoil designs are used, then manufacturing simplicity is maintained, but noise generation from trailing-edge self-noise and wake interaction remains significant
Solution Approach 1:
The airfoil trailing edge is segmented into multiple discrete elements (first trailing edge element, second trailing edge element, and intermediate trailing edge elements) rather than being a single continuous structure. This segmentation allows each element to be independently optimized for noise reduction while maintaining overall airfoil functionality, directly addressing the technical contradiction by reducing noise through structural division.
Solution Approach 2:
The intermediate trailing edge elements are positioned at specific locations where the boundary layer thickness is approximately 5-15% of the trailing edge thickness, creating local quality variations in the trailing edge region. This local optimization targets the specific area where wake interaction noise is generated, allowing noise reduction without requiring complex modifications to the entire airfoil structure.
2Object-affected harmful factors
If trailing edge modifications are made to reduce noise, then noise reduction is achieved, but manufacturing complexity increases
Solution Approach 1:
The intermediate trailing edge elements are designed to be positioned during the airfoil manufacturing process based on predetermined boundary layer thickness criteria. By establishing the positioning criteria in advance (at 5-15% of trailing edge thickness from the airfoil surface), the manufacturing process can proceed systematically without requiring complex post-manufacturing adjustments, thus maintaining ease of manufacture while achieving noise reduction.
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 solution effectively reduces aeromechanical and aeroacoustic responses of downstream surfaces by enhancing wake mixing vorticity, leading to quieter operation by minimizing corner flow losses and associated drag.
Implementation Method 1
promoting wake mixing and reducing interaction noise through streamwise vortical mixing
Implementation Method 2
optimized for local boundary layer conditions and aerodynamic pressure distribution
Data Source
AI summary
An airfoil for a turbofan engine includes a first contoured sidewall, a second contoured sidewall, a leading edge, and a trailing edge with each extending in a spanwise direction defined between a root and a tip portion of the airfoil. The first contoured sidewall and the second contoured sidewall define an outer surface of the airfoil. The airfoil further includes a plurality of protrusions where each protrusion of the plurality of protrusions has a curvilinear shape and extends outwardly from the outer surface along at least one of the first contoured sidewall or the second contoured sidewall. The plurality of protrusions is defined downstream from a mid-point of a chord length of the airfoil and terminates upstream of the trailing edge.