Discrete Frequency Noise Generation From an Axial Flow Fan Blade Row

1970 ◽  
Vol 92 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Ramani Mani
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Acoustic Energy ◽  
Frequency Noise ◽  
Noise Generation ◽  
Two Dimensional ◽  
Axial Flow Fan ◽  
Fan Noise ◽  
Blade Row ◽  
Fan Blade

An analysis is presented which treats the noise generation from an axial flow fan row by given forces including the effects of a moving medium. The linearization of Euler’s equations to yield tractable problems for fan noise is discussed. The three-dimensional problem is decomposed into several two-dimensional problems. Finally, full details are given of a two-dimensional analysis to predict the amounts of acoustic energy, at the blade passing frequency and its harmonics, radiated up and downstream of a blade row due to its interaction with a neighboring row.

Application of casing treatment to an industrial axial-flow fan

1998 ◽  
Vol 212 (4) ◽  
pp. 225-233 ◽  
Author(s):  
S D Hill ◽  
R L Elder ◽  
A B McKenzie
Keyword(s):  
Axial Flow ◽  
Rotating Stall ◽  
Strain Gauges ◽  
Axial Flow Fan ◽  
Fan Noise ◽  
Flow Measurements ◽  
Casing Treatment ◽  
Blade Tip ◽  
Fan Blade ◽  
Insight Into

This paper deals with an experimental investigation into the influence of a vaned recess casing treatment on the performance of an industrial-type axial-flow fan with a hub-tip ratio of 0.4. The treatment has been tested in a variety of configurations relative to the fan, with an emphasis on the amount of fan blade tip exposure to the treatment. Two sets of blading, one of which is of the fully reversible type, have been investigated. Detailed flow measurements have been carried out with a slanted hot wire probe to provide an insight into the operation of the device and into the nature of the rotating stall in the solid casing configuration. Strain gauges have been employed to enable blade stresses to be recorded and an in-duct microphone to enable comparative tests on fan noise has also been used.

scholarly journals Performance Enhancement of an Induced Draught Axial Flow Fan Through Pressure Recovery

R&D Journal ◽  
2021 ◽  
Vol 37 ◽  
Author(s):  
G. M. Bekken ◽  
C. J. Meyer ◽  
S. J. van der Spuy
Keyword(s):  
Performance Enhancement ◽  
Three Dimensional ◽  
Axial Flow ◽  
Design Flow ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Axial Flow Fan ◽  
Conical Diffuser ◽  
Efficiency Increase ◽  
Annular Diffuser

ABSTRACT This study illustrates that downstream diffusers can significantly aid the performance of an induced draught axial flow fan. Two conical diffusers of length 0.2 and 0.4 times the fan diameter and an annular diffuser with a length equal to the fan diameter are tested. At the design flow rate of the fan, the short conical diffuser increases the available static pressure by 17.6 % and the static efficiency by 8.9 %. The medium-length conical diffuser increases it by 21.9 % and 11.7 %, respectively. The long annular diffuser produces a 28.2 % pressure increase and a 14.2 % efficiency increase. The paper also compares the obtained pressure recovery coefficients of the different discharge diffusers using two-dimensional axisymmetric and three-dimensional computations. It shows that the pressure at the outlet of the fan cannot be assumed to be equal to atmospheric pressure, as is prescribed by the fan testing standards. A new method of measuring pressure recovery from two-dimensional computations is proposed. Additional keywords: Pressure recovery, axial flow fan, diffuser.

scholarly journals Wake Decay: Effect of Freestream Swirl

1997 ◽  
Author(s):  
J. M. Brookfield ◽  
I. A. Waitz ◽  
J. Sell
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Mixing Rate ◽  
Rotating Blade ◽  
Blade Row ◽  
The Mean ◽  
The Difference ◽  
Fan Blade

A study of the effects of freestream swirl on the decay characteristics of wakes shed from a rotating blade row is presented. The freestream swirl behind the rotor causes the wakes to skew tangentially, stretching the wakes as they are convected from the rotor to the stator. The effect of stretching on wake decay is illustrated using a simplified two-dimensional model. The model is described and the results are compared to 1) measurements from a two-dimensional cascade facility where no stretching or skewing of the wakes occurs, 2) solutions obtained using a three-dimensional, Reynolds-averaged Navier-Stokes solver, and 3) experimental wake measurements taken behind a low hub-to-tip ratio fan. For typical fan geometries with hub-to-tip ratios of approximately 0.5 and rotor-stator spacings of one to two rotor chord lengths, the wake can be stretched by over 50 percent. The stretching increases the mixing rate which leads to a reduction in the mean wake velocity deficit of approximately thirty percent and a widening of the wake of about fifteen percent. These effects account for much of the difference seen between cascade wake measurements and those taken behind rotating fan blade rows. It is therefore important to include such effects when using cascade data for prediction of fluid mechanic, acoustic, or structural phenomena associated with fan wakes. Finally, the study also suggests a potential for small (< 3 dB) reductions in wake-stator interaction noise through tailoring the fan loading distribution to produce particular span wise wake decay characteristics.

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