• Title/Summary/Keyword: Turbulent Noise

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Optimization of the Gas Gas Heater Element for Desulfurization Equipment through Flow Analysis (유동해석을 통한 신형 탈황설비용 GGH 요소 최적화)

  • Ryu, B.J.;Oh, B.J.;Baek, S.G.;Kim, H.S.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.599-602
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    • 2008
  • This paper deals with the optimization of Gas-Gas-Heater elements for desulfurization equipment through flow analysis. The flow analysis model used in the paper is ${\kappa}-{\varepsilon}$ turbulent flow model. Temperature and flow velocity distributions for three types of panel elements are calculated. Through the analysis the following conclusions are obtained. Firstly, pressure differences of between inlet and outlet for three types of panel elements do not exceed in the standard pressure difference. Secondly, it is expected that NU-type panel element having wide area of heat transfer will be more effective in the aspect of the heat transfer.

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Vibration Analysis of Rotor System for Rotary Compressor Considering Hydrodynamic Force between Motor Rotor and Stator (전동기 공극부 냉매의 유막력을 고려한 로터리 압축기용 회전축계의 진동해석)

  • Kim, Yong-Han;Yang, Bo-Suk;Ahn, Byoung-Ha;Lee, Jang-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1058-1064
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    • 2000
  • The analysis of dynamic behaviour of rotor system for the rolling piston type rotary compressor considering hydrodynamic force between motor rotor and stator is presented. In addition to considering other dynamic, loads such as large unbalance forces, gas force and bearing force, we consider the hydrodynamic force induced by the compressed fluid flow through the air gap between motor rotor and stator, and improve the analysis of vibration in rotary compressor. The Childs' method which based on Bulk-now and Hirs' turbulent lubrication model is used to calculate the rotordynamic coefficients due to hydrodynamic force of annular clearance in motor air gap.

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Rotordynamic and Leakage Analysis for Stepped-Labyrinth Gas Seal (압축기용 계단식 래버린스 실의 누설 및 동특성해석)

  • Ha, Tae-Woong;Lee, An-Sung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1084-1089
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    • 2000
  • The basic equations are derived for the analysis of a stepped labyrinth gas seal which are generally used in high performance compressors, gas turbines, and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the stepped labyrinth gas seal. The leakage and rotordynamic characteristic results of the stepped labyrinth gas seal are presented and compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula.

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Hypersonic Panel Flutter Analysis Using Coupled CFD-CSD Method

  • Tran, Thanh Toan;Kim, Dong-Huyn;Oh, Il-Kwon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.171-177
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    • 2011
  • In this paper, a square simply supported panel flutter have been considered at high supersonic flow by using coupled fluid-structure (FSI) analysis that based on time domain method. The Reynolds-Average Navier Stokes (RANS) equation with Spalart-Allmaras turbulent model were applied for unsteady flow problems of panel flutter. A fully implicit time marching schemed based on the Newmark direct integration method is used for calculating the coupled aeroelastic governing equations of it. In addition, the SOL 145 solver of MSC.NASTRAN was used to investigate flutter velocity based on PK-method of Piston theory. Our numerical results indicated that there is a good agreement result between Piston Theory in MSC.NASTRAN and coupled fluid-structure analysis.

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Voiced/Unvoiced/Silence Classification웨 of Speech Signal Using Wavelet Transform (웨이브렛 변환을 이용한 음성신호의 유성음/무성음/묵음 분류)

  • Son, Young-Ho;Bae, Keun-Sung
    • Speech Sciences
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    • v.4 no.2
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    • pp.41-54
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    • 1998
  • Speech signals are, depending on the characteristics of waveform, classified as voiced sound, unvoiced sound, and silence. Voiced sound, produced by an air flow generated by the vibration of the vocal cords, is quasi-periodic, while unvoiced sound, produced by a turbulent air flow passed through some constriction in the vocal tract, is noise-like. Silence represents the ambient noise signal during the absence of speech. The need for deciding whether a given segment of a speech waveform should be classified as voiced, unvoiced, or silence has arisen in many speech analysis systems. In this paper, a voiced/unvoiced/silence classification algorithm using spectral change in the wavelet transformed signal is proposed and then, experimental results are demonstrated with our discussions.

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An Experimental Study on Flow Noise with Swirl in a 180 Degree Circular Tube (선회가 있는 180°원형 곡관의 유동소음에 대한 실험적 연구)

  • Chang, Tae-Hyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.6
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    • pp.903-911
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    • 2009
  • During the past three or four decades, the characteristics of turbulent swirling flow have been studied extensively because of their scientific and academic importance. This research deal with the periodic flow oscillation with and without swirling flow in a 180 degree circular tube using hot wire anemometry, microphone and accelerometer. The frequency regions are observed through the structured oscillation from spectrum. This work carried out to measure the sound level by using hot wire anemometry, microphone and accelerometer for each Reynolds number, $6{\times}10^4$, $8{\times}10^4$ and $1{\times}10^5$ respectively at the entry of the test tube with and without swirl flow.

Prediction of Wear Depth of SG Tube based on Types of Wear Scar (전열관의 마모 체적형상에 따른 마모깊이 예측)

  • Ryu, Ki-Wahn;Kim, Hyung-Jin;Park, Chi-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.475-478
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    • 2005
  • Calculation of wear depth with regard to the wear topology is peformed numerically Four typical wear topology, that is round, crescent, flat, and diamond types are adopted to represent the configuration of wear volume. Diamond and flat types are the most severe topology for wear depth history, whereas round and crescent types have small increasing rate of wear depth to the wear volume. Based on this study we can guess that the most severe wear phenomena happens to be upper side of U-tubes in the KSNP SG, because flat or diamond wear will be generated by the wearing motion between tubes and diagonal, vertical, horizontal strips. The misalignment of tube at the stage of manufacturing or distortion of upper structure due to the thermal expansion or vibration of upper structure such as diagonal, vertical, and horizontal strips will be one of the main causes of flat or diamond wear.

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Development of Internal Inflow/outflow Steady Mean Flow Boundary Condition Using Perfectly Matched Layer for the Prediction of Turbulence-cascade Interaction Noise (난류-캐스케이드 상호작용 소음 예측을 위한 Perfectly Matched Layer을 이용한 내부 입/출구 정상유동 경계조건의 개발)

  • Kim, Dae-Hwan;Cheong, Cheol-Ung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.7
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    • pp.685-691
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    • 2012
  • It is essential for the accurate time-domain prediction of broadband noise due to turbulence-cascade interaction to develop inflow/outflow boundary conditions to satisfy the following three requirements: to maintain the back ground mean flow, to nonreflect the outgoing disturbances and to generate the specified input gust. The preceding study showed that perfectly matched layer(PML) boundary condition was successfully applied to absorb the outgoing disturbances and to generate the specified gust in the time-domain computations of broadband noise due to interaction of incident gust with a cascade of flat-plates. In present study, PML boundary condition is extended in order to predict steady mean flow that is needed for the computation of noise due to interaction of incident gust with a cascade of airfoils. PML boundary condition is originally designed to absorb flow disturbances superimposed on the steady meanflow in the buffer zone. However, the steady meanflow must be computed before PML boundary condition is applied on the flow computation. In the present paper, PML equations are extended by introducing source term to maintain desired mean flow conditions. The extended boundary condition is applied to the benchmark problem where the meanflow around a cascade of airfoils is predicted. These illustrative computations reveal that the extended PML equations can effectively provide and maintain the target meanflow.

A Stochastic Control for Nonlinear Systems under Random Disturbance Based on a Fluid Motion (유체운동에 의한 불규칙 가진을 받는 비선형계의 확률제어)

  • Oh, Soo-Young;Kim, Yong-Kwan;Cho, Lae-Kyoung;Choi, Young-Seob;Heo, Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.892-896
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    • 2001
  • Investigation is performed on the stability of nonlinear system under turbulent fluid motion modelled as white noise random process, which is a preliminary result in the course of research on the characteristic and nonlinear control of the stochastic system. Adopted physical model is beam-type structure with tip-mass and main base mass. The governing equation is derived via F-P-K approach in stochastic sense. By means of Gaussian Closure method infinite dynamic moment equations due to system nonlinearity is closed to finite one. At the best of authors' knowledge, it is the first trial to design nonlinear controller by using of sliding mode technique in stochastic domain and control performance and effect in stochastic domain is studied.

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LES Studies on the Characteristics of Turbulent Premixed Flame with the Configurations of Burner Exit (버너 출구의 형상변화에 따른 난류 예혼합 화염의 특성에 관한 LES 연구)

  • Hwang, Cheol-Hong;Lee, Chang-Eon
    • 한국연소학회:학술대회논문집
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    • 2006.04a
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    • pp.96-104
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    • 2006
  • In the present paper, the effects of combustion instability on flow structure and flame dynamic with the configurations of burner exit in a model gas turbine combustor are investigated using large eddy simulation(LES). A G-equation flamelet model is employed to simulate the unsteady flame behavior. As a result of mean flow field, the change of divergent half angle(${\alpha}$) at burner exit results in variations in the size and shape of the central toroidal recirculation(CTRZ) as well as flame length by changing corner recirculation zone(CRZ). The case of ${\alpha}=45^{\circ}$ show smaller size and upstream location of CTRZ than that of $90^{\circ}$ and $30^{\circ}$ by the development of higher swirl velocity. The flame length in the case of ${\alpha}=45^{\circ}$ is the most shortest, while that in the case of ${\alpha}=30^{\circ}$ is the longest by the decrease of effective reactive area with the absence of CRZ. Through the analysis of pressure fluctuation, it is identified that the case of ${\alpha}=45^{\circ}$ shows the most largest damping effect of pressure oscillation in all configurations and brings in the noise reduction of 2.97dB, comparing with that of ${\alpha}=30^{\circ}$ having the largest pressure oscillation. These reasons are discussed in detail through the analysis of unsteady phenomena about recirculation zone and flame surface. Finally the effects of flame-acoustic interaction are evaluated using local Rayleigh parameter.

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