• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.71-76
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• 2009

In a running blower, there are various exciting forces which can generate noise. The noise of an running industrial fan or blower depends on the structure of a fan, the machining accuracy of each element, and assembled conditions. Many studies have been carried out to reduce the noise of it. In this study, 3-hole buffs are used in pipe of blower to study the influence the number and position of buffs on the noise reduction at inlet and outlet in pipe. Commercial engineering software ANSYS and SYSNOISE were employed to analyze the characteristics and reduction ratio of pressure. It is concluded that optimal position and number of buffs in pipe of blower to show the least reduction ratio of pressure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.185-190
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• 2001

The structure borne noise of the air-conditioner, which degrades the noise quality, is hardly reduced by the general noise treatments. It can be effectively reduced by eliminating the structural vibration which the noise originates from. The rubber vibration isolator prevents the dynamic force induced by the fan driving motor from exciting the chassis structure, which finally reduces the structure borne noise. The dynamic properties of the vibration isolation system such as the natural frequency of the vibration isolation and loss factor of the rubber isolator, need to be experimentally evaluated. In this paper, these dynamic properties were obtained by the resonant method using the impact hammer for 3 types of the isolator specimens. It is known that the isolation natural frequency of the axial direction of the rubber isolator is two times higher than that of the radial direction, and is proportional to the hardness of the rubber specimen.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.396-401
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• 2000

It is addressed that the turbulent broadband sound power from a sirocco fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer on the blade. The design parameters such as solidity(c/s) and stagger angle are specified to predict performance and noise level because the separation and slip velocity are strongly affected by them along with the flow coefficient. This paper reports the effects of the solidity and the stagger angle upon the trailing edge noise from the circular arc-shaped blade of sirocco fan.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.82-87
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• 2007

A cleaner has trouble with too much noise and power consumption. To solve these problems, the investigation for motors, which are the main component of vacuum cleaner, is required. However, it is difficult to analyze the flow by the experimental means because of the high speed of the fan rotation ranging from 30,000 rpm to 50,000 rpm. Moreover it takes much time to perform the numerical simulation for the flow. In this research, it is aimed to analyse the flow through the centrifugal fan which is believed to be a main noise source, by the computational method. The efficiency of the centrifugal fan is affected by friction loss, shock loss and so on. Those losses depend on factors like the velocity of impeller, blade shape and etc. Accordingly, the influence of the shape of impeller on the flow is investigated in this study. The computational analysis was done by changing impeller shapes. The flow around the centrifugal fan is simulated by applying the moving mesh. To verify the validity of the computation results, the air flow rate and the pressure field to the cleaner is compared with the experimental data. All simulations are performed by using commercial code SC/Tetra. The calculated results show good agreement with the experimental ones qualitatively and it is believed to be promising to use computational simulation in the improvement of the vacuum cleaner performance.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.767-770
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• 2002

The performance and noise characteristics of the design parameters of a cross-flow fan are investigated by computational methods. The incompressible Wavier-Stokes equations in moving coordinates are time-accurately solved for obtaining the pressure fluctuations due to the aerodynamic interactions between the impeller blades and the stabilizer, and sound pressure is then computed by the Ffowcs Williams-Hawkings equation. Design parameters of the cross-flow fan include blade setting angle, exit-diffusion angle, and stabilizer installation angle. Also, an optimization of the aforementioned design parameters has been peformed using the Taguchi method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.737-742
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• 2011

Because of complex structure of inlet and outlet flows, the performance of centrifugal fans used in a household refrigerator is affected by many parameters of duct system surrounding the fans. In this paper, the performance of a centrifugal fan is numerically analysed according to shapes of inlet bell-mouth. To improve performance of the centrifugal fan, some design parameters are selected for comparison. On a basis of these comparison, optimum shape of inlet bell-mouth is proposed to maximise the flow rate of the fan.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.75-81
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• 2000

Vibration problems induced by an air cooled heat exchanger with axial flow fan were investigated during the operation of a petrochemical plant. Two different studies were done; one was experimental field test and the other was theoretical verification. To find main cause of the blade passing frequency of the fan after installing additional blockage board at the air inlet of the axial fan, the frequency spectrum was measured. The vibrations of the blade passing frequency became higher. The natural frequency of driving support of the heat exchanger was theoretically calculated. It was approximately equal to the blade passing frequency. During the normal operation of the plant, it was impossible to modify the structure of the driving support. Instead, the blade number was increased to reduce vibration level. It increased the ratio of the forcing frequency to the natural frequency of the driving support over the resonance region.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.14-16
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• 2010

A Duct surrounding a fan is known to reduce the tip loss and increase the fan performance efficiency. It also reduces the fan noise drastically. Ducted fan, therefore, has been focused to be a promising candidate for high efficient propulsion system. In this study, a small plane having ducted fan which can be tilted for vertical take-off and landing, is analyzed by CFD and its aerodynamic characteristics are compared. Ductef fan aircraft has small range of angle of attack for mininum drag and duct design should be focused for efficient ducted fan aircraft.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.433-438
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• 1999

This paper describes Active Noise Cancellation/Control(ANC) method that removes the information of the unnecessary noise and doesn't remove the informations of the necessary noise(warning sound, operating sound etc.) for the induced noise of the mechanical system. In this paper, the noise source Is axial fan, and the Feedback Active Noise control method that can effectively control BPF generated from the axial fan is used, and the Filtered-X LMS algorithm for adaptive algorithms is used. The experiments are executed for two case(propagating noise in the duct, emission noise for exterior free field). The part to be removed is BPF noise, and the band-pass filter not to effect to the other frequencies is used. Also, to investigate the effect of the noise reduction for human, we are compared with the results that are controlled for using Loudness before and after. As a results, we are certified that the BPF is decreased only and frequencies outside of BPF are not affected, and we acquire the reduction effects of 6.7 dB Loudness Level, then the frequency to be removed is controlled. Therefore, we can be certified that sound pressure as well as loudness can be effectively decreased for human sound quality

• Journal of Drive and Control
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• v.18 no.1
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• pp.1-8
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• 2021

This paper presents research on methods for the reduction of forklifts' noise level for the increased comfort and safety of its operator. A cooling fan with a high air volume flow rate installed in the forklift acts as an important design parameter which efficiently cools the heat exchanger system, helping to transfer internal heat from the engine room to the outdoors with both transmitted and diffracted opening noises. The cooling fan contributes significantly to both the forklift's emitted sound power and the operator room's noise level, thereby necessitating research on the forklift's reduction of acoustic power level and transmission. A noise analysis for various fan models with a biomimetic design based on eagle-wing geometry was conducted. In addition to the acoustic power generation, the aerodynamic performance of the cooling blade is also strongly influenced by the design of airfoil distribution, thereby requiring optimization. The cooling fans were fabricated and installed in the forklift in order to check the efficacy of the forklift engine's cooling, and the final version of the fan was measured for its ability to lower acoustic power level and cool the engine room. This study explains the aerodynamic and acoustic features of the designed fans with the use of BEM analysis and forklift test results.