Development and Application of Fan Noise Prediction Method to Axial and Centrifugal Fan

2002 ◽  
Author(s):  
Duck-Joo Lee ◽  
Wan-Ho Jeon ◽  
Ki-Hoon Chung
Keyword(s):  
Flow Field ◽  
Free Field ◽  
Sound Field ◽  
Solid Boundary ◽  
Centrifugal Fan ◽  
Acoustic Analogy ◽  
Axial Fan ◽  
Fan Noise ◽  
Scattering Effect ◽  
Numerical Predictions

Numerical predictions of fan noise have not been studied extensively. This is due to the scattering effect of the fan casing, duct and the difficulty in obtaining aerodynamic acoustic source. New method to predict the fan noise and performance is developed and used to calculate various fan noise problems. A vortex method is used to model the fan and to calculate the flow field. Acoustic pressures are obtained from the unsteady force fluctuations of the blades using an acoustic analogy. But the acoustic analogy can be applied only in the free field in general. In order to consider the solid boundary effects of the casing, the newly developed Kirchhoff-Helmholtz BEM (Boundary Element Method) is introduced. With the above-mentioned method, the flow field and sound field of centrifugal and axial fan were calculated. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal sound. Also, in the predicted sound field, we can see the scattering effect of duct and casing.

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.

Development of an Ultra-Quiet Fan for Computer Cooling Applications

2014 ◽  
Author(s):  
Zhenyu Wang ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Field Measurements ◽  
Vortex Structures ◽  
Tip Clearance ◽  
Axial Fan ◽  
Fan Noise ◽  
Piv Measurements ◽  
Cooling Fan

We report the progress made in our recent study to develop an ultra-quiet axial fan for computer cooling applications. By using a commercially-available cooling fan as the baseline, a number of acoustically tailored modifications are implemented in order to reduce the noise level of the cooling fan, which includes optimizing the rotator blades and guide vanes according to axial fan design theory, adding an intake cone in the front of the hub to guide the airflow into the axial fan smoothly, and reducing the tip clearance to lower the noise generation due to tip vortex structures. A comparison study is conducted to measure the sound pressure level (SPL) of the reformed axial fan in an anechoic chamber, in comparison to that of the prototype fan, in order to assess the effects of the modifications on the fan noise reduction. The measurement results of our preliminary study reveal that, at the same flow rate, the SPL of the reformed fan would be up to 5 dB lower than that of the prototype fan. In addition to measuring the sound pressure levels (SPLs) of the fans, a digital particle image velocimetry (PIV) system is also used to conduct detailed flow field measurements to reveal the changes of the flow characteristics and unsteady vortex structures associated with the modifications. Besides conducting “free-run” PIV measurements to determine the ensemble-averaged statistics of the flow quantities such as mean velocity, Reynolds stress, and turbulence kinetic energy (TKE) distributions at the exit of the axial fan, “phase-locked” PIV measurements are also performed to elucidate further details about evolution of the unsteady vortex structures in fan exhaust in relation to the position of the rotating fan blades. The detailed flow field measurements are correlated with the SPL measurements in order to elucidate underlying physics associated with the fan noise reduction.

scholarly journals Numerical simulation of leakage flow field and acoustic characteristics for safety valve

2021 ◽  
Vol 336 ◽  
pp. 01007
Author(s):  
Fan Qian ◽  
Minghui Hu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Pressure Fluctuation ◽  
Large Scale ◽  
Safety Valve ◽  
Sound Field ◽  
Wall Pressure ◽  
Small Scale ◽  
Acoustic Analogy ◽  
Wall Pressure Fluctuation

Aiming at the internal leakage problem of spring type nuclear safety valve at the sealing surface, the flow field and sound field characteristics at the leakage height of 0.5mm between the valve disc and the valve seat sealing surface were studied, and the numerical simulation was carried out based on large eddy simulation(LES) and mohring acoustic analogy method, and compare the effects of acoustic wall pressure fluctuation(AWPF) and turbulent wall pressure fluctuation(TWPF) as the excitation source on the external sound field of the valve. The simulation results show that: the change gradient of velocity field and pressure field at the leakage port of safety valve is significant and form vortices of different sizes. The small-scale vortices are mainly in the leakage port, while the large-scale vortices mainly exist in the flow channel; When the valve is leaking, the noise is mainly dominated by high-pressure injection noise, its spectrum curve shows wide-band characteristics, and the external noise of the valve is mainly caused by AW P F. The above research results can provide a theoretical basis for the safety valve online detection method.

Numerical Simulation and Experimental Research of Hydrophone Flow Noise

2020 ◽  
Author(s):  
Mingyuan Li ◽  
Jianzhang Liu ◽  
Yan Wei ◽  
Fengzhong Qu ◽  
Minhao Zhang ◽  
...  
Keyword(s):  
Flow Field ◽  
Acoustic Communication ◽  
Communication System ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Sound Field ◽  
Underwater Acoustic Communication ◽  
Acoustic Analogy ◽  
Underwater Acoustic ◽  
Flow Noise

Abstract Underwater acoustic communication is an important technology in deep-sea research. In underwater acoustic communication system, when hydrophone as acoustic receiver is exposed to sea environment and moves along with an underwater vehicle, its performance is prone to be affected by various ambient noises, among which its generated flow noise is the major source. This would especially influence the performance and shorten the communication distance of underwater acoustic communication system. In this paper, we try to unveil how the flow field is correlated with the flow noise of hydrophone. The Large Eddy Simulation (LES) method and acoustic analogy were used to simulate the flow field and the sound field around hydrophone, respectively. The flow noise of hydrophone at different moving velocities was obtained. Then experiments in an anechoic tank were carried out to verify the simulation results. The subsequent analysis of the experimental results shows that the flow noise has obvious influence on underwater communication, and as the hydrophone moves faster, its sound pressure level climbs up higher. This study also further verifies the reliability of simulating the flow noise of bare hydrophone by computational fluid dynamics, and provides the theoretical basis for improving the signal-to-noise ratio of low-frequency underwater acoustic communication system.

Three-Dimensional Numerical Simulation of the Whole Flow Field on Centrifugal Fan

2012 ◽  
Vol 251 ◽  
pp. 15-20
Author(s):  
Bo Wan ◽  
Xue Fei Liang ◽  
Tao Sun
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Flow Field ◽  
Three Dimensional ◽  
Air Cooling ◽  
Cooling Towers ◽  
Centrifugal Fan ◽  
Axial Fan ◽  
Grain Drying ◽  
Turbo Machinery

Centrifugal fan is a kind of widely used turbo machinery. It is widely used in buildings, mines, factories, tunnels, vehicles, ships and air cooling towers and cooling; grain drying and sending; inflatable hovercraft and propulsion. It has many advantages compared to axial fan. In this paper, we study the numerical simulation of the whole flow field of a High-pressure centrifugal fan called 9-16№15.9D.The researches can contribute to a better design on centrifugal fan.

An Experimental and Computational Study on the Aerodynamic and Acoustic Characteristics of Case Fans

2015 ◽  
Author(s):  
Zhenyu Wang ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Numerical Study ◽  
Field Measurements ◽  
Vortex Structures ◽  
Tip Clearance ◽  
Axial Fan ◽  
Fan Noise ◽  
Cooling Fan

We report the progress made in our recent study to develop an ultra-quiet axial fan for computer cooling applications. By using a commercially-available cooling fan as the baseline, a number of acoustically tailored modifications are implemented in order to reduce the noise level of the cooling fan, which includes optimizing the rotating blades and guide vanes according to axial fan design theory, adding an intake cone in the front of the hub to guide the airflow into the axial fan smoothly, and reducing the tip clearance to lower the noise generation due to tip vortex structures. A comparison study is conducted to measure the sound pressure level (SPL) of the new-design axial fan in an anechoic chamber, in comparison to that of the baseline fan, in order to assess the effects of the modifications on the fan noise reduction. The measurement results of our study reveal that, at the same flow rate, the SPL of the new-design fan would be up to 5 dB lower than that of the baseline fan. In addition to measuring the sound pressure levels (SPLs) of the fans, a digital particle image velocimetry (PIV) system is also used to conduct detailed flow field measurements to reveal the changes of the flow characteristics and unsteady vortex structures associated with the modifications. “Time-averaged” PIV measurements illustrate the ensemble-averaged statistics of the flow quantities such as mean velocity, Reynolds stress, and turbulence kinetic energy (TKE) distributions at the flow field around the axial fan. Moreover, a numerical study of the new-design fan is also performed and which is aimed to investigate the flow details inside of the fan. The validation comparison between numerical results and experimental results agree very well and that gives the strong confidence for the computational flow field in the fan can be regarded as useful complement for experiments. The detailed flow field measurements are correlated with the SPL measurements in order to elucidate underlying physics associated with the fan noise reduction.

Experimental and Numerical Investigation of the Aerodynamic Noise Radiated From a Centrifugal Blower

2015 ◽  
Author(s):  
Jiandong Chen ◽  
Beibei Sun ◽  
Jianrun Zhang ◽  
Fei Xue ◽  
Xin Liu
Keyword(s):  
Three Dimensional ◽  
Prediction Method ◽  
Aerodynamic Noise ◽  
Centrifugal Fan ◽  
Centrifugal Blower ◽  
Fan Noise ◽  
Large Eddy Simulation Model ◽  
Scattering Effect ◽  
Eddy Simulation ◽  
Numerical Result

Centrifugal blowers are widely used as garden machines, however, the aerodynamic noise generated by these machines cause serious problems. Although many researches focus on the generation mechanism and prediction method of centrifugal fan noise, most of these researches analysis the simplified centrifugal fan models and ignore the diffraction and scattering effect. In this paper, both experimental and numerical methods are carried out to analysis and measure the aerodynamic noise of the centrifugal blower. In order to calculate the flow field, a CFD (Computational Fluid Dynamics) numerical model is established, and the LES (Large Eddy Simulation) model is used to solve the three-dimensional unsteady flow, while the FW-H (Ffows Williams-Hawkings) model is used to calculate the acoustic source. To consider the diffraction and scattering effect, a BEM method is used to predict the sound radiated from the blower. A parallel experiment is carried out to measure the aerodynamic noise in a semi-anechoic room, and the numerical result shows a good agreement with the experiment result. The effect of outlet and inlet ducts on the sound radiation of the centrifugal blower is also investigated in this paper.

Application of acoustic analogy to automotive engine-cooling fan noise prediction

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1095-1098 ◽  
Author(s):  
Jeonghan Lee ◽  
Kyungseok Cho ◽  
Soogab Lee
Keyword(s):  
Noise Prediction ◽  
Acoustic Analogy ◽  
Fan Noise ◽  
Automotive Engine ◽  
Engine Cooling ◽  
Cooling Fan

scholarly journals Analysis of the Influence of Different Bionic Structures on the Noise Reduction Performance of the Centrifugal Pump

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 886
Author(s):  
Cui Dai ◽  
Chao Guo ◽  
Yiping Chen ◽  
Liang Dong ◽  
Houlin Liu
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Centrifugal Pump ◽  
Great Influence ◽  
Frequency Doubling ◽  
Sound Field ◽  
Internal Flow ◽  
Test System ◽  
Centrifugal Pumps ◽  
External Characteristics

The strong noise generated during the operation of the centrifugal pump harms the pump group and people. In order to decrease the noise of the centrifugal pump, a specific speed of 117.3 of the centrifugal pump is chosen as a research object. The bionic modification of centrifugal pump blades is carried out to explore the influence of different bionic structures on the noise reduction performance of centrifugal pumps. The internal flow field and internal sound field of bionic blades are studied by numerical calculation and test methods. The test is carried out on a closed pump test platform which includes external characteristics and a flow noise test system. The effects of two different bionic structures on the external characteristics, acoustic amplitude–frequency characteristics and flow field structure of a centrifugal pump, are analyzed. The results show that the pit structure has little influence on the external characteristic parameters, while the sawtooth structure has a relatively great influence. The noise reduction effect of the pit structure is aimed at the wide-band noise, while the sawtooth structure is aimed at the discrete noise of the blade-passing frequency (BPF) and its frequency doubling. The noise reduction ability of the sawtooth structure is not suitable for high-frequency bands.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

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