Effect of inlet reflections on fan noise radiation

AIAA Journal ◽  
1996 ◽  
Vol 34 (9) ◽  
pp. 1771-1777 ◽  
Author(s):  
H. D. Meyer
Keyword(s):  
Fan Noise ◽  
Noise Radiation

Fan Casing Noise Radiation

1991 ◽  
Vol 113 (1) ◽  
pp. 37-42 ◽  
Author(s):  
G. H. Koopmann ◽  
W. Neise ◽  
K. A. Cunefare
Keyword(s):  
Sound Pressure ◽  
Noise Spectrum ◽  
Centrifugal Fan ◽  
Noise Sources ◽  
Fan Noise ◽  
Noise Radiation ◽  
Starting Point ◽  
Element Program ◽  
Inlet Box ◽  
Subharmonic Frequency

This paper presents a method for assessing the extent of casing noise radiation of a centrifugal fan relative to the aeroacoustic sources associated with the inlet box of the fan. Central to the method is a boundary element program which is used to compute the acoustic pressures on the surfaces of the fan casing in terms of its surface vibration which in this case was measured experimentally. Data from an earlier experiment was used as the starting point for this study. Available data included sound pressure measurements near and away from the inlet box of the fan and vibration measurements over the casing of the fan. Noise from the outlet duct of the fan was purposely highly attenuated. Computations of sound pressure, intensity, and power indicated that, at the blade passing frequency (300 Hz), the aerodynamic sources generated near the entrance plane of the inlet box of the fan dominate the noise spectrum in the field. On the other hand, at the first subharmonic frequency of the blade tone (150 Hz), the sound power generated from the inlet box and fan casing are within 3 dB of each other. Thus, for effective noise control at this frequency, it would be necessary to include both noise sources in the overall treatment.

scholarly journals Lifting Fan Noise Studies

1969 ◽  
Author(s):  
G. Krishnappa ◽  
G. G. Levy
Keyword(s):  
Experimental Investigation ◽  
Aerodynamic Characteristics ◽  
Broadband Noise ◽  
Fan Noise ◽  
Noise Radiation ◽  
Close Spacing ◽  
Blade Passing Frequency ◽  
Low Levels ◽  
High Level ◽  
Inflow Conditions

The paper reviews the results of an experimental investigation of noise radiated from a VTOL lifting fan inlet under static inflow conditions. The results are discussed in the light of recent theoretical and experimental conclusions on compressor noise radiation, combined with relevant data on the aerodynamic characteristics of the fan. The presence of high level discrete tones, up to four harmonics of the blade passing frequency superimposed over a broadband noise extending from 200 to 15,000 cps, is attributed to close spacing between rotor and stator blades, Low levels of broadband noise were observed to be caused by low levels of turbulence at the intake. Analysis of the limited results shows the variation of broadband noise as the sixth power of the velocity of the flow relative to the blade.

Axisymmetric computations of fan noise radiation from turbofan inlets

1999 ◽  
Author(s):  
D. Ait-Ali-Yahia ◽  
D. Stanescu ◽  
W. Habashi ◽  
M. Robichaud
Keyword(s):  
Fan Noise ◽  
Noise Radiation

Wave envelope and infinite element schemes for fan noise radiation from turbofan inlets

AIAA Journal ◽  
1984 ◽  
Vol 22 (12) ◽  
pp. 1719-1726 ◽  
Author(s):  
R. J. Astley ◽  
W. Eversman
Keyword(s):  
Fan Noise ◽  
Infinite Element ◽  
Noise Radiation
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