• Title/Summary/Keyword: Flow Noise

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Experimental and Analytical Study on the Flow Noise Reduction of Construction Equipment (건설장비의 유동 소음 저감을 위한 해석 및 실험적 연구)

  • Kim, Hyung-Taek;Joo, Won-Ho;Bae, Jong-Gug
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2010.05a
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    • pp.242-243
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    • 2010
  • The cooling system, including a fan is a one of the major sources to generate the radiated noise of construction equipment. Therefore, it is required to reduce the flow noise induced by a fan in order to reduce the noise level. In this study, we made an engine room model to carry out a variety of experiments. And then, the flow noise analysis technique using the CFD code was applied to the cooling system of construction equipment. These analyses results agree well with the measurement results. These results make it possible to understand the flow noise characteristics and to design the low noise cooling system in the design stage.

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Reduction of Refrigerant-induced Noise of the Refrigerator by Modification of the Evaporator Inlet Pipe (증발기 입구 배관의 구조 개선을 통한 냉장고 냉매 소음 저감)

  • Kim, Min-Seong;Han, Hyung-Suk;Kim, Tae-Hun;Jeong, Wei-Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.10
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    • pp.1012-1020
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    • 2009
  • This research is focused on the experimental study of the noise induced by two-phase refrigerant flow in the evaporator. The two-phase flow in the evaporator has various flow patterns. The effects of two-phase flow pattern's characteristics on the noise of the evaporator are investigated experimentally. The experimental data shows that the generated noise is mainly related to the layout of the pipe and the certain two-phase flow patterns such as the churn and slug flow. Based on these results, we removed the unnecessary vertical pipe and changed the pipe diameter of the evaporator - inlet into small one in order to avoid the intermittent flow condition. The noise level of newly-designed inlet-pipe of the evaporator was measured experimentally by refrigerant-supplying equipment and compared with that of conventional one.

Experimental Study on the Design Parameter Effects on the Flow-rate and the Noise level in a Cross-flow Fan (실험에 의한 직교류홴의 유량 및 소음 분석)

  • Ahn, Cheol-O;Rew, Ho-Seon
    • The KSFM Journal of Fluid Machinery
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    • v.1 no.1 s.1
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    • pp.41-48
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    • 1998
  • This study was carried out to investigate the effect of design parameters on the volume flow-rate and the noise level and to finally find the optimal design variables. Eighteen cross-flow fans were designed by the method of orthogonal array, and the flow-rate and the noise level were measured. These data were analyzed by the neural network system. The effects of eight design variables(scroll exit angle, scroll arc length et al.) on the fan performance and the noise level were valuated and discussed. This experiment shows that the design solutions suggested by neural network system may increase its volume flow-rate and reduce noise simultaneously.

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A Study on Discrete Frequency Noise from a Symmetrical Airfoil in a Uniform Flow (에어포일 이산소음 특성에 관한 연구)

  • Kim, H. J.;Lee, S.;N. Fujisawa
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.365.2-365
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    • 2002
  • The flow field around a symmetrical airfoil in a uniform flow under the generation of noise was studied by experiments and numerical simulation. The experiments are conducted by visualizing the surface flow over the airfoil with a shear-sensitive liquid-crystal coating and by measuring the instantaneous velocity field around the trailing edge of the airfoil. The numerical simulation was carried out by LES. (omitted)

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Supersonic Jet Noise Control via Trailing Edge Modifications

  • Kim, Jin-Hwa;Lee, Seungbae
    • Journal of Mechanical Science and Technology
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    • v.15 no.8
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    • pp.1174-1180
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    • 2001
  • Various experimental data, including mixing areas, cross correlation factors, surface flow patterns on nozzle walls, and far field noise spectra, was used to draw a noise control mechanism in a supersonic jet. In the underexpanded case, mixing of the jet air with ambient air was significantly enhanced as presented before, and mixing noise was also dramatically reduced. Screech tones, in the overexpanded case, were effectively suppressed by trailing edge modifications, although mixing enhancement was not noticeable. From mixing and noise performance of nozzles with modified trailing edges, enhancing mixing through streamwise vortices seems an effective way to reduce mixing noise in the underexpanded flow regime. However, screech tones in the overespanded flow regime is well controlled or suppressed by making shock cells and/or spanwise large scale structures irregular and/or less organized by a proper selection of trailing edges. The noise field in the overexpanded flow regime was greatly affected by the symmetricity of the nozzle exit geometry. In the underexpanded flow regime, the effects of the symmetricity of the nozzle exit on mixing were negligible.

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A Computerized Design System of the Axial Fan Considering Performance and Noise Characteristics (성능 및 소음특성을 고려한 축류 팬 설계의 전산 체계)

  • Lee, Chan;Kil, Hyun-Gwon
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.2
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    • pp.48-53
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    • 2010
  • A computerized design system of axial fan is developed for constructing 3-D blade geometry and predicting both aerodynamic performance and noise. The aerodynamic blading design of fan is conducted by blade angle distribution, camber line determination, airfoil thickness distribution and blade element stacking along spanwise distance. The internal flow and the aerodynamic performance of designed fan are predicted by the through-flow modeling technique with flow deviation and pressure loss correlations. Based on the predicted internal flow field and performance data, fan noise is predicted by two models for discrete frequency and broadband noise sources. The present predictions of the flow distribution, the performance and the noise level of actual fans are well agreed with measurement results.

Characteristics of Flow-Induced Noise around a Sphere (구 주위의 유동으로 인해 발생하는 유동 소음의 특성)

  • Yun, Gi-Woong;Choi, Hae-Cheon
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.810-815
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    • 2003
  • Flow-induced noise propagated from flow over a sphere is numerically investigated for laminar flow at Re = 300 and 425, and for turbulent flow at Re = 3700 and $10^4$, where the Reynolds number is based on the freestream velocity and the sphere diameter. The numerical method used for obtaining the flow over a sphere is based on an immersed boundary method in a cylindrical coordinate system. The Curle’s solutions of the Lighthill’s acoustic analogy with and without the far-field and compact-source approximation are used in order to investigate the noise field from flow over a sphere. Since the drag and lift forces change irregularly in time at Re = 425, 3700 and $10^{4}$, the noise propagates in a complicated manner. At Re = 300, 425 and $10^{4}$, the noise from dipole sources is much larger than that from quadrupole sources. On the other hand, at Re = 3700, the quadrupole source becomes dominant. The temporal variation of the flow-induced noise around a sphere is obtained at some observation points, which shows that the peak frequency corresponds to the Strouhal number associated with the wake instability.

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Study on Noise Reduction of An Axial Flow Fan According to the System Characteristics (시스템 특성을 고려한 축류팬 저소음화에 대한 연구)

  • Yoon, Hong-Yeol;Kim, Chang-Jun;Song, Sung-Bae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1381-1385
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    • 2000
  • In this paper, a guideline of axial flow fan design for noise reduction of refrigerators is p resented. Refrigerators have components which have a role to screen particular frequency air borne-noise which is generated by an axial flow fan set in them. Effective ways to use the particular characteristic of refrigerators are shown in this study. As a result of application of the methods, we reduced the noise of the target systems by more than 3 dB(A) from the viewpoint of air-borne noise produced by the axial flow fan set.

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Experimental study on the design parameter effect on the noise in the cross flow fan (실험에 의한 CROSS FLOW FAN 소음 분석)

  • 안철오;류호선
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.615-620
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    • 1997
  • The flow rate and the noise level of 18 cross flow fans were measured to analyze the effect of design variables on these and to finally find the optimal design value. These data were analyzed by the Taguchi method and the neural network. The optimal values obtained by the neural network showed good agreements with that by the Taguchi method. The effects of eight design variables on the fan performance and the noise were evaluated and discussed.

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Development of shipboard large-sized low-noise room unit with multiple outlets (다수의 출구를 가진 선박용 대형 저소음 룸유닛 개발)

  • Kim, Sang-Ryul;Kim, Hyun-Sil;Lee, Sung-Hyun;Park, Geun-Hyo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.04a
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    • pp.600-605
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    • 2012
  • In this paper, the acoustic performance of a shipboard large-sized room unit is studied. The room unit is a kind of rectangular absorptive chamber with a partition whose surface absorptive material with fabric skin is attached to. The room unit has one inlet and three outlet. At the inlet, a plane damper is installed to control the flow rate. The acoustic performance of a prototype room unit is measured using a HVAC mock-up. It is shown that its insertion loss is comparable with that of a commercially-used room unit but the developed room unit generates flow noise higher than the other one. The major source of flow noise is analyzed by NADS-R, the noise analysis program for room unit. Cone-shaped dampers are proposed to be used as the damper of a room unit to reduce flow noise. It is shown that the cone-shaped damper decrease flow noise remarkably.

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