Turbomachine Blade Sweep Angle for Tone Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aero gas turbine engines face significant noise challenges due to tone noise generated by fan blades, particularly at supersonic operating conditions, which is difficult to attenuate effectively with existing noise reduction methods.
Innovation Solution
The blade design is optimized by varying the leading edge sweep angle along the radial direction to direct acoustic power into better attenuated acoustic modes, using techniques such as computational fluid dynamics to minimize noise at the blade passing frequency and its harmonics, and shaping the blade to produce specific pressure shocks that enhance noise attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional noise reduction methods (acoustic liners, stator vanes) are used to attenuate tone noise, then noise levels are reduced, but the methods are ineffective at supersonic operating conditions and require complex modifications to existing blade designs
Solution Approach 1:
The patent applies local quality by varying the leading edge sweep angle at different radial positions along the blade. The sweep angle is not uniform but is optimized locally at each spanwise location to direct acoustic power into specific acoustic modes that are better attenuated by the intake liner, thereby reducing tone noise without requiring complex overall blade redesign
Solution Approach 2:
The patent changes the geometric parameter of the leading edge sweep angle along the radial direction. By adjusting this parameter distribution, the blade modifies the acoustic power distribution across different radial modes, directing energy into modes that experience higher attenuation in the lined intake, thus reducing overall tone noise effectiveness
2Object-affected harmful factors
If the blade leading edge sweep angle is varied to direct acoustic power into attenuated modes, then tone noise is significantly reduced, but the blade design becomes more complex and harder to manufacture
Solution Approach 1:
The patent applies local quality by varying the leading edge sweep angle at different radial positions along the blade. The sweep angle is not uniform but is optimized locally at each spanwise location to direct acoustic power into specific acoustic modes that are better attenuated by the intake liner, thereby reducing tone noise without requiring complex overall blade redesign
Solution Approach 2:
The patent introduces a dynamic characteristic by making the sweep angle variable along the radial direction rather than fixed. This dynamic geometric variation allows the blade to adaptively direct acoustic power into different modes depending on the radial position, achieving noise reduction while maintaining manufacturability through a systematic variation pattern
3Object-affected harmful factors
If existing fan blade designs are used, then fan efficiency and foreign object damage resistance are maintained, but tone noise at supersonic operating conditions remains high
Solution Approach 1:
The patent applies local quality by varying the leading edge sweep angle at different radial positions along the blade. The sweep angle is not uniform but is optimized locally at each spanwise location to direct acoustic power into specific acoustic modes that are better attenuated by the intake liner, thereby reducing tone noise without requiring complex overall blade redesign
Solution Approach 2:
The patent segments the blade leading edge into multiple radial zones, each with a different optimized sweep angle. This segmentation allows different portions of the blade to perform different functions: directing acoustic power into specific modes while maintaining overall fan efficiency and reliability characteristics
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 approach significantly reduces tone noise by directing acoustic power into more attenuated modes, resulting in a substantial decrease in noise levels, with the acoustic power of the least attenuated radial mode being more than 5 dB lower than the total acoustic power, effectively addressing the noise reduction challenges in aero gas turbine engines.
Implementation Method 1
tone noise is produced by shock waves emanating from the fan blades and propagating upstream through the engine intake
Implementation Method 2
line the intake and bypass ducts with panels that absorb the sound produced by the fan system
Data Source
AI summary
A blade for a turbomachine extends in use, in a radial direction relative to the axis of the turbomachine. The turbomachine has at least one operating condition which generates supersonic fluid flow at the blade. The blade is adapted to provide, at the supersonic operating condition, a leading edge sweep angle which varies such that successive radial positions (i) to (iii) along the leading edge are at respective sweep angle turning points. Position (i) is the radially inner and position (iii) the radially outer of the positions. Position (i) is at or radially outward of the 30% span position, where 0% span is the radially innermost point of the leading edge and 100% span is the radially outermost point of the leading edge.