• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.380-387
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• 2000

In this paper, a successful result of modification of an axial flow fan and a shroud for noise reduction of a window type air conditioner is presented especially in order to verify the importance of blade shape improvement and the searching for the optimal shape of shrouds. Effective ways to work out the result as mentioned above are to make the tip of the blade varied in thickness and to have special shapes. From the viewpoint of the shape in a shroud, several cases were examined and the particular value of a design parameter of the shroud was acquired to get the best noise reduction of an air conditioner. Through the application of the methods, the air conditioner became less noisy by 4.5 dB(A) in terms of air-borne noise produced only by the axial flow fan and consumed less energy by 20.9% compared to the current one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.778-784
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• 2002

FFU are used increasingly by the microeleceronics industry to provide clean recirculating air for the fabrication of integrated circuits and laminar flow air. There may be several hundred ffu in a large cleanroom, covering 100% of the ceiling area. Hence, there is of often knowledge in the inside and outside of the country the flu give rise to noise & vibration trouble to microelectronics industry. Noise ＆ Vibration control for satisfication about noise ＆ vibration criteria in TFT-LCD factory cleanroom be in need of exact noise & vibration data of accurence from utility & equipment that can be exert a bad influence upon cleanroom. In this pater, hence we found out noise and vibration properities of ffu by using experimental method. And, we performed noise ＆ vibration analysis about noise it vibration level in cleanroom using semiempirical method for quantative approach about noise ＆ vibration level in cleanroom.

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.555-565
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• 2021

The goal of this study is to improve flow and noise performances of existing backward-curved blade centrifugal fan system used for circulating cold air in a refrigerator freezer by optimally designing airfoil shape. The unique characteristics of the system is to drive cold airflow with two volute tongues in combination with duct system in a back side of a refrigerator without scroll housing generally used in a typical centrifugal fan system. First, flow and noise performances of existing fan system were evaluated experimentally. A P-Q curve was obtained using a fan performance tester in the flow experiment, and noise spectrum was measured in an anechoic chamber in the noise experiment. Then, flow characteristics were numerically analyzed by solving the three-dimensional unsteady Navier-Stokes equations and noise analysis was performed by solving the Ffowcs Williams and Hawkins equation with input from the flow simulation results. The validity of numerical results was confirmed by comparing them with the measured ones. Based on the verified numerical method, blade inlet and outlet angles were optimized for maximum flow rate using the two-factor central composite design of the response surface method. Finally, the flow and noise performances of a prototype manufactured with the optimum design were experimentally evaluated, which showed the improvement in flow and noise performance.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.213-216
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• 2006

This paper was a study about noise reduction through flow stabilization in duct using experimental method and numerical analysis at the same time. To determine the fan's type three kinds of fans(axial fan, centrifugal fan, and axial fan with centrifugal type blades) was examined to investigate the suitability for in-line duct. As a result, under the equal number of rotation 2000 RPM, performance of an axial fan with centrifugal type blades was the most superior by 55dBA at 4.3CMM among other fans. After this, analyzed the results of the numerical analysis to find out the optimum design of pitch angle such as $0^{\circ}$, $10^{\circ}$, $15^{\circ}$ and $20^{\circ}$. The intensity of turbulence was low when pitch angle was $15^{\circ}$ and air volume became peak by 5.08 CMM. It was observed that axis component of velocity increased gradually when pitch angle increased from $0^{\circ}$ to $20^{\circ}$, and embodied noise reduction and improvement of air flow rate through flow stabilization.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.321-327
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• 2019

The purpose of this study is paper is to improve the flow performance and to reduce the aerodynamic noise of air discharge system consisting of a centrifugal fan, ducts and a housing for the clothes dryer. Using computational fluid dynamics and acoustic analogy based on FW-H (Ffowcs-Williams and Hawkings) Eq., air flow field and acoustic fields of the air discharge system are investigated. To optimize aerodynamic performance and aerodynamic noise, the response surface method is employed. The two factors central composite design using the inflow and outflow angles of fan blades is adopted. The devised optimum design shows the reduction of turbulent kinetic energy in the ducts and the housing of the system, and as a result, the improved flow rate and reduce noise is confirmed. Finally, the experment using the proto-type manufactured usign the optimum design shows the increase of flow rate by 4.2 %.

• The KSFM Journal of Fluid Machinery
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• v.17 no.1
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• pp.35-40
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• 2014

A multi-objective optimization of a regenerative fan for enhancing the aerodynamic and aeroacoustic performance was carried out using an integrated fan design system, namely, Total FAN-Regen$^{(R)}$. The Total FAN-Regen$^{(R)}$ was developed for non-specialists to carry out a series of design process, viz., computational preliminary design, three-dimensional aerodynamic and aeroacoustic analyses, and design optimization, for a regenerative fan. An aerodynamic analysis of the regenerative fan was conducted by solving three-dimensional Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. And, an aeroacoustic analysis of the regenerative fan was implemented in a finite/infinite element method by solving the variational formulation of Lighthill's analogy based on the results of the unsteady flow analysis. An optimum shape obtained by Total FAN-Regen$^{(R)}$ shows the enhanced efficiency and decreased sound pressure level as much as 1.5 % and 20.0 dB, respectively, compared to those of the reference design. The performance test was carried out for an optimized regenerative fan to validate the performance of the numerically predicted optimal design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.652-657
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• 2002

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 stagger angle upon the trailing edge noise for various trailing edge shapes. It is believed that the serrated trailing edge provides break-up mechanism for organized convecting vortices, thereby reduce the overall noise level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.488-489
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• 2014

This paper is a case study for the reduction of excavator Radiated noise. The main purpose of the study is to reduction noise for the cooling fan and hydraulic line which is main noise source of the excavator. Recent, noise regulations for the construction equipment is becoming stricter. Compare to past excavator drivers requirements for noise level demanding are becoming more and more. Therefore, this progress is an important role in determining the quality of the excavator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.946-950
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• 2006

This paper proposed the ways for reduction of the prominent peak of the tone noise in air conditioning units. In order to find out the sources of the tone noise, the resonant frequencies and modes of the fans were investigated. Also, the effects of the ambient temperatures and material properties of the fans on the tone noise were studied. From the experiments, it was shown that the tone noise was greatly influenced by the torsional resonance of the fan and motor system and commutation frequency. In other words, the torsional resonance of the fan and motor system has not to be close to the commutation frequency (torque ripple frequency) which creates a rate of change in the angular acceleration in order to reduce the tone noise in air conditioning units.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.630-636
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• 2008

1000MW급 증설과 관련하여 발전소 주변지역으로부터 민원이 제기된 3000MW급 화력발전소는 넓은 평지에 위치하여 발전소의 영향이 그대로 주변지역에 전달되는 상태임에도 일상 소음레벨이 환경 기준치를 만족하는 상태였으나 향후 증설에 따른 소음도 증가에 대비하여 소음영향을 예측하고 저감 대책을 검토하였다. 대형 화력발전소의 옥외소음원은 Booster fan, I.D.fan, 주변압기, 대형 철탑, 해수순환수 펌프 전동기, 증기방출관 등이 있다. 대상 주거지역의 경우는 대형팬에 의한 지향성이 크게 나타났다. 따라서, 발전소가 주변지역에 주는 소음별 기여도를 평가하고 영향이 큰 대형팬에 대한 대책으로써 기기주변에 방음벽을 설치하는 방안과 함께 소음원의 크기를 저감시킬 수 있는 소음기 대책을 추천하여 증설 예정호기를 비롯한 기존 호기중 주거지역에 영향이 큰 3000MW에 대하여 수립함으로써 소음저감 목표치를 달성하는 결과를 도출하였다.