Unstady Flow within Centrifugal Fan Casing and the Mechanism of Noise Generation
| Project/Area Number |
59460088
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | Waseda University |
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Principal Investigator |
YOSHIOKA Eisuke (1985-1986) Professor, Department of Mechanical Engineering, Waseda University, 理工学部, 教授 (50063699)
大田 英輔 (1984) 早稲田大学, 理工学部, 教授
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| Co-Investigator(Kenkyū-buntansha) |
KAWASE Takehiko Professor, Department of Mechanical Engineering, Waseda University, 理工学部機械工学科, 教授 (60063690)
TAJIMA Kiyohiro Professor, Department of Mechanical Engineering, Waseda University, 理工学部機械工学科, 教授 (60063335)
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| Project Period (FY) |
1984 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1985: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1984: ¥3,400,000 (Direct Cost: ¥3,400,000)
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| Keywords | Fluid Machinery / Centrifugal Fan / Fan Noise / Unsteady Internal Flow / 3-Dimensional Numerical Analysis / Surge Similation / Similarity Rule of Noise Prediction / サージ |
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| Research Abstract |
A fundamental study approaching a similarity rule of the centrifugal fan noise and flow mechanism related to the low frequency system oscillation is made by the following investigations;
(1) The blade passing frequency noise, say BPF noise, is expressed in terms of a machine dependent factor, a rotational-speed dependent factor, an attenuation factor between the 1st and the 2nd mode of the BPF noise, and a frequency response function expressing the acoustic propagation characteristics. Each level and the geometrical parameters of the factors are determined by experiments. The frequency response function is estimated by a plane acoustic model analysis.
(2) Three dimensional flow field within the fan casing is discussed by measurements of pressure fluctuation, and by inviscid numerical analysis applying the FLIC method and the DENTON technique. The levels and the spetial distributions of fluctuation components due to the impeller discharge and secondary flow related to the casing geometry
… More
are to be distinguished.
(3) A numerical method to simulate the low frequency system oscillation is concerned by introducing the pressure-flow rate characteristic of the fan and one dimensional expressions of the system passages.
The results and the future prospects of the research are obtained as follows;
(a) The noise prediction rule is found very satisfactory, and the frequency response function is described by the length and the cross-sectional area of the blade-to-blade passage and the fan inlet duct. Without reduction of the fluid machinery efficiency, a noise suppression of 25 dB is found possible by a suitable selection of the fan geometry.
(b) Within the casing, fluctuation due to the secondary flow is not significant in compared to the turbulent mixing. The major fluctuation distributes only on the side wall area very close to the cut-off of the scroll, and this is due to the impeller discharge.
(c) The three dimensional numerical analysis and the one dimensional simulation method are found to lead satisfactory results. These method will be applied to a further analysis about the unsteady blade passage flow during the system oscillation at a low discharge operation. Less
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Report
(1 results)
Research Products
(10 results)
