Annular Splitter Wall Serrations for Turbomachine Broadband Noise
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Solution Overview
Problem
Aero-acoustic management in turbomachines and profiled airflow structures is challenging due to broadband noise generated by the interaction of fan wakes with inlet and outlet guide vanes, which affects aerodynamic properties and requires noise reduction without compromising lift and boundary layer stability.
Innovation Solution
The turbomachine incorporates profiled structures with serrations featuring individually inclined teeth and angularly offset recesses, optimized in orientation and shape to minimize noise impact while adapting to rotational influences, with options for fixed or variable tooth inclinations based on engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If serrated profile structures are used to reduce broadband noise, then acoustic noise levels are reduced, but aerodynamic properties (aerodynamic losses, lift, boundary layer stall) are significantly affected
Solution Approach 1:
The patent applies different geometric characteristics to different parts of the serrated profile. The teeth have specific height, spacing, and inclination angles that are optimized locally to reduce noise while the overall profile geometry is designed to minimize aerodynamic disruption. This local optimization allows noise reduction without compromising global aerodynamic performance.
Solution Approach 2:
The serrated profile features asymmetric tooth geometry with specific inclination angles relative to the airflow direction. The teeth are not symmetric but have predetermined angles that are optimized to reduce broadband noise while maintaining favorable aerodynamic characteristics, resolving the contradiction between noise reduction and aerodynamic performance.
2Volume of moving object
If the fan diameter is increased and nacelle length is reduced to decrease distance between fan and guide vanes, then engine size is optimized, but interaction of fan wake with guide vanes increases broadband noise
Solution Approach 1:
The patent converts the harmful wake interaction into a beneficial effect by using the serrated profile structures on guide vanes. These serrations are specifically designed to interact with the fan wake in a controlled manner, reducing broadband noise while allowing the compact engine configuration to be maintained. The harmful wake interaction is transformed into a noise-reduction mechanism.
3Object-affected harmful factors
If teeth of serrated profile are individually inclined to face airflow globally oblique to general axis, then noise reduction effectiveness is improved, but manufacturing complexity increases
Solution Approach 1:
The serrated profile is divided into multiple individual teeth, each with a predetermined inclination angle. This segmentation allows each tooth to be independently optimized for noise reduction while the overall pattern can be manufactured using standardized processes. The complex inclined geometry is broken down into repeatable modular tooth elements.
Solution Approach 2:
The patent specifies predetermined parameters for tooth inclination angles, heights, and spacing that optimize noise reduction. By defining these parameters in advance, the complex geometry can be consistently manufactured using controlled parameter variations rather than requiring complex adaptive manufacturing processes.
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 reduces acoustic noise levels while maintaining aerodynamic performance by aligning serration surfaces with airflow directions and adapting to rotational changes, thus optimizing both aero-acoustic and mechanical aspects.
Implementation Method 1
profiled structures having a profiled leading and/or trailing edge having, along a leading and/or trailing edge line, a serrated profile thus provided with a succession of teeth and hollows... serrated airfoils are capable of reducing broadband noise
Implementation Method 2
the airflow generated axially (X-axis hereafter, also called the general axis) downstream of a rotating structure... is vortex-driven and strongly influenced by a direction of air rotation
Data Source
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AI summary
An aircraft turbine engine comprises an annular wall (160) for splitting a flow of air, downstream of an upstream fan (14), first stationary blades (24) for guiding a primary flow and the second stationary guidance blades (26) attached to the annular splitting wall (160), the wall being provided with at least one profiled structure for air flow having a profiled leading edge exhibiting a profile (28) with serrations exhibiting a succession of teeth (30) and troughs, such that, along the leading edge from a first location (21) to a second location (23), the teeth are individually inclined towards the second location, either towards an oblique orientation of the air flow, or in the direction of the line (240) of camber of the first blades. Alternatively, the troughs (32) are angularly interposed between two first circumferentially consecutive blades.