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Vibration analysis and noise reduction of the swinging unit. Noise components of ducted fans. Flow source Trace noise Noise of the turbulent boundary layer Noise of the separated flow region Mechanical source Noise of the drive train Noise of the excited cover Noise of the PWM control. - PowerPoint PPT Presentation
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1 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Vibration analysis and noise reduction of the swinging unit
2 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Noise components of ducted fans
• Flow source Trace noise Noise of the turbulent boundary layer Noise of the separated flow region
• Mechanical source Noise of the drive train Noise of the excited cover Noise of the PWM control
3 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Flow source noises
• Trace noise
• Noise of the turbulent boundary layer
0
0
drag
lifting
F
FS
4 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Flow source noises
•Noise of the separated boundary layer
Proper and improper constructions for the entrance region
(1) Separation bubble (1) Laminar sublayer(2) Turbulent boundary
layer
5 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Mechanical source noises
Finite element modal analysis
•DOF: 162168•N. of elements: 26824 •Solver: COSMOS
Mesh: Mode shape at 48.55 Hz:
6 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Mechanical source noises
Results
Number of natural frequencies in each 20 Hz range
7 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Measurement
• Four-channel-measurement 2 accelerometers microphone tachometer
8 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Measurement
Zero pitch
Max pitch direction 1
Max pitchdirection 2
9 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Waterfall diagrams
Microphone signal compared with finite element results
10 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Waterfall diagrams
Microphone signal scaled by rpm
11 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Waterfall diagrams
The 8 kHz PWM noise appearing in the signal of the 2nd accelerometer
12 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
The 8 kHz PWM noise appearing in the signal of the microphone
13 / 13Vibration analysis and noise reduction of the swinging unitMagyar Bálint (BME)Magyar Bálint (BME)
A C R O B O T E R 3rd3rd OSB meeting OSB meeting Reading, Reading, 22-23 22-23 / / 1111 / 2007 / 2007
Conclusions
Reduction or elimination of noise components
• Flow source components Trace noise - Not significant Noise of the turbulent boundary layer - By choosing better airfoil Noise of the separated flow region - Proper contstruction of the
entrance region
• Mechanical source components Noise of the excited cover - By increasing stiffness, rarefying
natural frequencies Noise of the PWM control - By raising controller frequency
above human hearing limit
Estimated total possible noise reduction:dBALA 86
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