1 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Vibration analysis and noise reduction of the swinging unit
2 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 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 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Flow source noises Trace noise Noise of the turbulent boundary layer
4 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 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 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Mechanical source noises Finite element modal analysis DOF: N. of elements: Solver: COSMOS Mesh:Mode shape at Hz:
6 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Mechanical source noises Results Number of natural frequencies in each 20 Hz range
7 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Measurement Four-channel-measurement 2 accelerometers microphone tachometer
8 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Measurement Zero pitch Max pitch direction 1 Max pitch direction 2
9 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Waterfall diagrams Microphone signal compared with finite element results
10 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Waterfall diagrams Microphone signal scaled by rpm
11 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 Waterfall diagrams The 8 kHz PWM noise appearing in the signal of the 2nd accelerometer
12 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 2007 The 8 kHz PWM noise appearing in the signal of the microphone
13 / 13 Vibration analysis and noise reduction of the swinging unit Magyar Bálint (BME) A C R O B O T E R 3rd OSB meeting Reading, / 11 / 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: