• Title/Summary/Keyword: Numerical Calculation

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Optimization of the Heat Input Condition on Arc Welding (아아크 용접시 입열 조건의 최적화에 관한 연구)

  • 박일철;박경진;엄기원
    • Journal of Welding and Joining
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    • v.10 no.2
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    • pp.32-42
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    • 1992
  • A method of optimization of process parameters in Arc Welding has been discussed in this paper. The method of investigation is based on the numerical calculation of weld bead by a finite element method and non-linear optimization technique is applied to estimated the optimization process parameters from the numerical calculation. The common package program(ANSYS 4.4A) was used to obtain the process parameters for a thin plate arc welding (TIG, CO$_{2}$). The results on some test are satisfactory and the used method of this paper is a useful guide to the optimum welding condition.

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A Numerical Analysis of Acoustic Characteristics in Gas Turbine Combustor with Spatial Non-homogeneity (불균질한 온도장을 고려한 가스터빈 연소기의 음향장 해석)

  • Sohn, Chae-Hoon;Cho, Han-Chang
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1292-1297
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    • 2004
  • Acoustic characteristics in an industrial gas-turbine combustor are numerically investigated by adopting linear acoustic analysis. Spatially non-homogeneous temperature field in the combustor is considered in the numerical calculation and the characteristics are analyzed in view of acoustic instability. Acoustic analysis are conducted in the combustors without and with acoustic resonator, which is one of combustion stabilization devices. It has been reported that severe pressure fluctuation frequently occurs in the adopted combustor, and the measured signal of pressure oscillation is compared with the acoustic-pressure response from the numerical calculation. The numerical results are in a good agreement with the measurement data. In this regard, the phenomenon of pressure fluctuation in the combustor could be caused by acoustic instability. The acoustic effects of the resonators are analyzed in the viewpoints of both the frequency tuning and the damping capacity.

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Numerical Calculation of the free-Surface Flows around a Submerged Body (잠수체 주위 자유표면 유동의 수치계산)

  • 김용직;하영록;홍사영
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.2
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    • pp.11-20
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    • 2003
  • In this paper, the high-order spectral/boundary-element method is developed to calculate the 3-dimensional water waves generated by a submerged body. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated Tn time-domain. Three-dimensional free-surface flows generated by a submerged sphere which is moving under the free-surface are calculated. Through example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown. Comparisons with others' results show good agreements.

THIN SHELL FORMATION TIME AND [OIII] LINE IN FAST WIND BUBBLE (빠른 항성풍 거품의 구각형성 시각과 [OIII]선의 형성)

  • Choi, Seung-Eon;Lee, Yeong-Jin
    • Publications of The Korean Astronomical Society
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    • v.11 no.1
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    • pp.91-107
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    • 1996
  • We determine analytically the onset of thin-shell formation time of fast wind bubble with power-law energy injection $E_{in}=E_0t^s$, and power-law ambient density structure, ${\rho}_0(r)={\bar{\rho}}(r/{\bar{r}})^{-{\omega}}$. Thin-shell formation time, $t_{sf}$ can be estimated by minimizing the total time elapsed before the complete cooling of shocked gas. For uniform medium (${\omega}=0$) and constant energy injection (s = 1), the onset of shell formation is found to be at $t_{sf}=5.2{\times}10^3yr$, which agrees Quite well with the results of FCT 1D numerical calculation. We solve the line transfer problem with previous result derived by numerical calculation in order to calculate line profile of [OIII] (${\lambda}=5007{\AA}$) forbidden line. In general, radiative outer shell causes the formation of double peaked line profile. Each peak corresponds to approaching and receeding shells with large velocities. Our line profiles show good agreements with observation of expanding shell structure.

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INFLUENCE OF THE MIXING RATIO OF DOUBLE COMPONENTIAL FUELS ON HCCI COMBUSTION

  • Sato, S.;Kweon, S.P.;Yamashita, D.;Iida, N.
    • International Journal of Automotive Technology
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    • v.7 no.3
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    • pp.251-259
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    • 2006
  • For practical application on the HCCI engine, the solution of subjects, such as control of auto-ignition timing and avoidance of knocking, is indispensable. This study focused on the technique of controlling HCCI combustion appropriately, changing the mixture ratio of two kinds of fuel. Methane and DME/n-Butane were selected as fuels. The influences, which the mixing ratio of two fuels does to ignition timing, ignition temperature, rate of heat release and oxidation reaction process, were investigated by experiment with 4-stroke HCCI engine and numerical calculation with elementary reactions.

Numerical Calculation of Permeability in Resin Transfer Molding (수지 이송 성형에서 투과율 계수의 수치적 계산)

  • Song, Young-Seok;Youn, Jae-Roun
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2003.10a
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    • pp.83-86
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    • 2003
  • Complete prediction of second order permeability tensor for three dimensional preform such as plain woven fabric and braided preform is critical to understand the resin transfer molding process of composites. The permeability can be obtained by various methods such as analytic, numerical, and experimental methods. For several decades, the permeability has studied numerically to avoid practical difficulty of many experiments. However, the predicted permeabilities are a bit wrong compared with experimentally measured data. In this study, numerical calculation of permeability was conducted for two kinds of preforms i.e., plain woven fabric and circular braided preform. In order to consider intra-tow flow in the unit cell of preform the proposed flow coupled model was used for plain woven fabric and the Brinkman equation was solved in the case of the braided preform.

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Performance Evaluation and Numerical Calculation of Flows through a Vaned Diffuser for Centrifugal Compressor (원심압축기용 베인 디퓨저 내부유동의 수치해석 및 성능평가)

  • Choi, Yun-Ho;Kang, Shin-Hyoung;Lee, Jang-Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.10
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    • pp.1296-1309
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    • 1999
  • A three dimensional compressible Navier-Stokes code is developed to analyze flowfields and performance of a vaned diffuser in a centrifugal compressor. It employs scalar implicit approximate factorization, finite volume formulation, second order upwind differencing and a two-equation $q-{\omega}$ turbulence model based on the integration to the wall. Pressure recovery and loss coefficients of a vaned diffuser are evaluated using a developed computer code. The simulated three dimensional flows show how through flow structure affects pressure recovery performance and loss coefficients of a vane for design and off-design inlet flow angles. Development of complex three dimensional flow over the inlet region and leading edge are very influential to the overall flow and performance.

Numerical Calculation of Minimum Ignition Energy for Hydrogen and Methane Fuels

  • Kim, Hong-Jip;Chung, Suk-Ho;Sohn, Chae-Hoon
    • Journal of Mechanical Science and Technology
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    • v.18 no.5
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    • pp.838-846
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    • 2004
  • Minimum ignition energies of hydrogen/air and methane/air mixtures have been investigated numerically by solving unsteady one-dimensional conservation equations with detailed chemical kinetic mechanisms. Initial kernel size needed for numerical calculation is a sensitive function of initial pressure of a mixture and should be estimated properly to obtain quantitative agreement with experimental results. A simple macroscopic model to determine minimum ignition energy has been proposed, where the initial kernel size is correlated with the quenching distance of a mixture and evaluated from the quenching distance determined from experiment. The simulation predicts minimum ignition energies of two sample mixtures successfully which are in a good agreement with the experimental data for the ranges of pressure and equivalence ratio.

Numerical Calculations and Analyses in Diagonal Type Magnetohydrodynamic Generator

  • Le, Chi Kien
    • Journal of Electrical Engineering and Technology
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    • v.8 no.6
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    • pp.1365-1370
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    • 2013
  • This paper examines the effects of magnetic induction attenuation on current distribution in the exit regions of the Faraday-type, non-equilibrium plasma Magnetohydrodynamic (MHD) generator by numerical calculation using cesium-seeded helium. Calculations show that reasonable magnetic induction attenuation creates a very uniform current distribution near the exit region of generator channel. Furthermore, it was determined that the current distribution in the middle part of generator is negligible, and the output electrodes can be used without large ballast resistors. In addition, the inside resistance of the exit region and the current concentration at the exit electrode edges, both decrease with the attenuation of magnetic flux density. The author illustrates that the exit electrodes of the diagonal Faraday-type, non-equilibrium plasma MHD generator should be arranged in the attenuation region of the magnetic induction, in order to improve the electrical parameters of the generator.

A Study on the Forging of Gears with lnternal Serrations (내부세레이션홈이 존재하는 외치차 단조에 관한 연구)

  • 최종용;조해용
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.633-637
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    • 1995
  • Numerical calculation tool for forging of gear-like components based on kinematically admissible velocity fields for upper bound method applicable to various deformation features of workpiece in forging processes were suggested. Each one of them deals with unidirectional flow of metal on dies, such as external involute spur gear, sequare spline, internal serrations. A complex calcuation tool of gear-like component forging process was built up by combining these kinematically velocity fields. In this paper, the workpiece with both external and internal teeth is divided into two parts. The deformation of each part is analyzed simultaneously using numerical calculation tool form combined kinematically admissible velocity field. The experimental set-up was installed in a 200 ton hydraulic press. As a result, each kinematically admissible velocity field could be combined with other and the calculated solution are useful to predict the capacity of forging equipment.

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