scholarly journals An Image Based Mathematical Model for the Propagation of Fan Noise in a Plenum with Large Side Openings

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Michael J. Panza
Keyword(s):  
Mathematical Model ◽  
Side Wall ◽  
Group Model ◽  
Image Model ◽  
Zero Sound ◽  
Noise Sources ◽  
Fan Noise ◽  
Air Inlet ◽  
Source Orientation ◽  
Reflecting Surfaces

This paper presents another application of an images group model for a special enclosure geometry and source orientation. A previous work outlined the concept via application to a special tight-fitting enclosure. Application of the concept to a fan plenum requires different mathematical descriptions for the image groups. This paper describes the sound reverberation inside a sound enclosure with mostly open sides where the primary noise sources are the air inlets and exhausts of axial type fans located at the top of the enclosure, the sound transmission through the air inlet openings, and the radiation to wayside positions. The main reverberation between the floor and ceiling is determined with an image based mathematical model. The model considers how the main reverberant part image group is amplified by its images from two parallel bulkheads and any side wall frame members. The method of images approach allows the hard surfaces of an untreated plenum to be represented by perfectly reflecting surfaces with zero sound absorption coefficients, thus not requiring any estimate or measurement for these surfaces. Numerical results show excellent comparison to experimental results for an actual plenum. The image model is also shown to be significantly more accurate than the standard large room diffuse field reverberant model.

Two-step computational aeroacoustics approach for underhood cooling fan application

2021 ◽  
Vol 263 (3) ◽  
pp. 3615-3624
Author(s):  
Parag Chaudhari ◽  
Jose Magalhaes ◽  
Aparna Salunkhe
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Air Flow ◽  
Computational Aeroacoustics ◽  
Noise Sources ◽  
Fan Noise ◽  
Cooling Fan ◽  
Sound Pressure Levels ◽  
One Step

Aeroacoustic noise is one of the important characteristics of the fan design. Computational Aeroacoustics (CAA) can provide better design options without relying on physical prototypes and reduce the development time and cost. There are two ways of performing CAA analysis; one-step and two-step approach. In one-step CAA, air flow and acoustic analysis are carried out in a single software. In two-step approach, air flow and acoustic analysis are carried out in separate software. Two-step CAA approach can expedite the calculation process and can be implemented in larger and complex domain problems. For the work presented in this paper, a mockup of an underhood cooling fan was designed. The sound pressure levels were measured for different installation configurations. The sound pressure level for one of the configurations was calculated with two-step approach and compared with test data. The compressible fluid flow field was first computed in a commercially available computational fluid dynamics software. This flow field was imported in a separate software where fan noise sources were computed and further used to predict the sound pressure levels at various microphone locations. The results show an excellent correlation between test and simulation for both tonal and broadband components of the fan noise.

A Ring Silencer Design for Reducing Noise of Axial Fan

2003 ◽  
Vol 03 (03) ◽  
pp. L259-L264
Author(s):  
Jian-Da Wu ◽  
Mingsian R. Bai
Keyword(s):  
Helmholtz Resonator ◽  
Boundary Region ◽  
Acoustic Analogy ◽  
Axial Fan ◽  
Noise Sources ◽  
Fan Noise ◽  
Fluctuating Pressure ◽  
Axial Fans ◽  
Fan Blade ◽  
Broadband Frequency

In this paper, a ring silencer design for reducing the noise of axial fans is presented. The noise sources on axial fans are usually caused by the fluctuating pressure distribution on the surface of fan blade. Most of the sources are near the trailing edge of blades or boundary region of blades. The ideation of proposed design is based on the principle of Helmholtz resonator for reducing the noise around the fan. The electro-acoustic analogy of this design is presented and simply discussed. Experimental measurement is carried out to evaluate the proposed design for reducing the axial fan noise. The result of experiment indicated that the ring silencer achieved 17 dB in blade passing frequency and 10 dB in other broadband frequency of power spectrum level.

scholarly journals Active control of periodic fan noise in laptops: spectral width requirements in a delayed buffer implementation

2009 ◽  
Vol 7 (02) ◽  
Author(s):  
H. A. Cordourier-Maruri ◽  
F. Orduña-Bustamante
Keyword(s):  
Active Control ◽  
High Performance ◽  
Active Noise Control ◽  
Spectral Width ◽  
Tonal Noise ◽  
Successful Operation ◽  
Noise Sources ◽  
Fan Noise ◽  
Audio Processing ◽  
Cooling Fans

An active control system intended for the reduction of strictly periodic noise components in computer cooling fans is described, which is based on high‐performance digital sound device architectures found in some personal computers. The system overcomes causality and synchronization constrains imposed by delayed buffering, as usually found in computer audio processing. Performance of the system is demonstrated and evaluated through measurements in a physical implementation of active noise control of synthetic tones combined with laptop fan noise, carried out under anechoic and slightly everberant conditions. Tests on other types of tonal noise sources, like an electrical transformer, were also carried out. However, its wider applicability to the cancellation of tonal noise has been proved compromised by weak periodicity issues found and reported in this work. Also, a study of noise spectral width requirements for successful operation is presented.

Numerical Analysis of an Industrial Fan Fitted With Noise Reduction Devices

2006 ◽  
Author(s):  
J. Amaral Teixeira ◽  
E. Naylor ◽  
P. C. Ivey ◽  
A. G. Sheard ◽  
I. R. Kinghorn
Keyword(s):  
Numerical Analysis ◽  
Noise Reduction ◽  
Flow Characteristics ◽  
Pressure Rise ◽  
Broadband Noise ◽  
Noise Sources ◽  
Fan Noise ◽  
Trailing Edge ◽  
Low Speed ◽  
The Individual

The reduction of noise emitted by industrial low speed cooling fans, particularly those fitted to air conditioning systems is a concern to fan manufacturers. The market for industrial low speed fans is highly competitive, with fan noise being the major differentiating factor between competing products. Noise reduction strategies are therefore implemented but these can adversely affect the fan’s pressure delivery capability. A reduction of fan speed can also lead to a reduction in fan noise but this is usually accompanied by a corresponding reduction in pressure rise and flow rate. The practical difficulties associated with maintaining fan pressure and flow characteristics while simultaneously reducing fan noise present fan manufacturers with a challenge. Traditional empirical approaches to the reduction of fan noise have almost been exhausted and no longer offer the potential to significantly reduce fan noise. The understanding of the aerodynamic mechanisms that act as broadband noise sources in low speed fans has been the subject of a considerable number of papers over many years. For most fans operating as a single blade row, the main sources of noise, other than those dependent on the incident turbulence levels, depend on the trailing edge and tip gap flow conditions. A range of strategies seeking to control the noise generated by these regions have been proposed over time by various authors and a number of these schemes have reached production status. The current paper details the numerical analysis of an industrial low speed fan, commonly used in conjunction with a cooling matrix, and which incorporates two distinct noise reduction features; trailing edge crenulations and a blade tip fence. Comparisons are carried out between various combinations of blades, with and without the individual features, and a discussion of the aerodynamics of the particular configurations is undertaken from a perspective of their noise reduction capabilities.

scholarly journals Mathematical study of transport phenomena along a tuyere of the Teniente converter

2006 ◽  
Vol 2006 ◽  
pp. 1-12
Author(s):  
J. San Martín ◽  
R. Gormaz ◽  
C. Conca ◽  
F.-Z. Saouri ◽  
A. Benaddi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Gas Flow ◽  
Refractory Lining ◽  
Transport Phenomena ◽  
Gas Velocity ◽  
Mathematical Study ◽  
Air Inlet ◽  
Solid Part ◽  
Velocity Pressure

This paper presents a comprehensive mathematical model of transport phenomena which occur along a tuyere of the Teniente converter during injection of oxygen-enriched air. Inlet pressure, gas velocity and temperature, the dimensions of the tuyere, and the properties of gas are the basic data. From these inputs, temperature distribution of the refractory walls of the converter around the tuyere as well as the velocity, pressure, and the Mach number along the pipe can be calculated. In this model, the heat transfer through the metal jacket of the tuyere and the refractory lining are duly taken into account. More precisely, a mathematical model is developed where the equations of momentum and energy of the gas are coupled with the equations of heat transfer inside the solid part. This new model couples a partial differential equation in the solid part with four ordinary differential equations in the gas flow.

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.

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