Turbomachine Fan Blade Protuberance for Vortex Noise Reduction
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Solution Overview
Problem
Turbomachines with unducted fans experience high operating acoustic levels due to aerodynamic interactions between contra-rotating fans, particularly at low-speed operations, where downstream blade-marginal vortex interactions dominate noise radiated, and current solutions like clipping are ineffective in the presence of external elements or incidence, degrading turbomachine efficiency.
Innovation Solution
The blade design features a single protuberance on the leading edge, positioned between 0.75 and 0.85 of the blade's height, creating two independent co-rotating vortices and contra-rotating auxiliary vortices to reduce noise by preventing vortex merging, with specific dimensions for the protuberance and optional notch to manage flow distribution effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If clipping is used to reduce downstream blade-marginal vortex interaction, then noise is reduced, but turbomachine efficiency is degraded
Solution Approach 1:
The invention applies local quality by introducing a protuberance at a specific location (0.75-0.85 of blade height) on the leading edge, creating localized flow modification. This targeted approach generates supplementary vortices that interact with marginal vortices locally, reducing noise without requiring global blade redesign that would compromise overall efficiency
Solution Approach 2:
The invention segments the vortex structure by creating multiple independent vortices (supplementary vortices from the protuberance and natural marginal vortices) instead of a single large vortex. This segmentation prevents the formation of large-scale coherent structures that cause strong noise, while maintaining the distributed vortex pattern needed for efficient momentum transfer
2Object-affected harmful factors
If clipping is used to reduce downstream blade-marginal vortex interaction, then noise is reduced, but the solution becomes ineffective in the presence of external elements or incidence
Solution Approach 1:
The invention applies preliminary action by pre-modifying the flow field upstream of the downstream fan through the protuberance-induced supplementary vortices. These vortices are generated in advance to interact with and disrupt the marginal vortices before they can cause strong blade-vortex interactions, providing robust noise reduction that works in both isolated and non-isolated configurations
Solution Approach 2:
The invention changes the flow parameters by introducing controlled vorticity through the protuberance geometry (height 0.05-0.2H, length 0.02-0.1H). This parameter modification creates a more resilient flow structure that maintains its noise-reducing effectiveness under varying operating conditions and in the presence of external elements
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 significantly reduces noise radiated by turbomachines by weakening downstream blade-marginal vortex interaction without degrading upstream fan performance, maintaining efficiency even in non-isolated configurations with external elements or incidence.
Implementation Method 1
The single protuberance is defined by its span position h such that 0.75 H ≤ h ≤ 0.85 H, so as to locally disturb, as the fan rotates, the distribution of the flow around the blade, so as to form two independent main vortices downstream
Implementation Method 2
the disturbing means comprising a single protuberance formed on the leading edge of the blade... locally disturb, as the fan rotates, the distribution of the flow around the blade
Implementation Method 3
the aerodynamic interaction between the upstream and downstream contra-rotating fans of such a turbomachine with unducted fan generates high operating acoustic levels... downstream blade-marginal vortex interaction dominates the radiated acoustic spectrum
Data Source
AI summary
A blade for a fan of a turbomachine, for example of unducted fan type, a corresponding fan, and a corresponding turbomachine. The blade includes a mechanism arranged, at a single location, to locally, as the fan rotates, disturb a distribution of flow around the blade so as to form two independent main vortices downstream.