2000 Fiscal Year Final Research Report Summary
Reduction of Centrifugal Blower Noise Using Active Noise Source Cancellation Method
| Project/Area Number |
10650187
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Waseda University |
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Principal Investigator |
OHTA Yutaka Waseda University, School of Science and Engineering, Professor, 理工学部, 教授 (50211793)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Fluid Machinery / Centrifugal Blower / Aerodynamic Noise / Blade Passing Frequency / Active Noise Control / Passive Noise Control / Noise Reduction |
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| Research Abstract |
Experimental and Analytical Approach has been conducted for these three years in order to present an effective evaluation and reduction methods for aerodynamic noise radiated from widely used centrifugal type of blower.
Experiments are focused on basic and higher-order of blade passing frequency (BPF) components of the radiated noise since these components show distinct peaks in power spectra and thus control the whole noise level. First, effective noise source region is experimentally determined using correlation method between the data of pressure fluctuation on the scroll surface and that of far field noise. The effective noise source region of basic BPF exists in the vicinity of the cut off apex as usually expected, while that of the higher-order BPF exists relatively downstream part on the scroll. Using this pattern of noise source distribution, active cancellation of BPF components are conducted by using piezoelectric actuators to oscillate the scroll surface directly. However, the presented active control is found to be very effective only for the higher-order BPF components because the pressure fluctuation level of basic BPF noise source is much larger than that of the secondary source. Then, another type of reduction method i.e. passive reduction method by changing geometric parameters of the blower, is necessary to have the complete noise reduction method. The passive reduction method is related to the characteristics of the noise transmission passage which is composed of some numbers of blade-to-blade passages and inlet duct. By adjusting the blade passing frequency to the maximum attenuation frequency of the frequency response function of the transmission passage, noise level of basic BPF can be reduced more than 20 decibels. The presented hybrid method of active and passive noise control is found to be effective against any types of radiated noise from centrifugal blower, and is the quite new type of noise reduction technique.
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