• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.133-141
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• 2000

The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The recently developed unsteady flamelet model has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations the further downstream.

• 한국분무공학회지
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• 제6권3호
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• pp.8-16
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• 2001

The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The unsteady flamelet model recently developed has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations further downstream.

• Journal of Mechanical Science and Technology
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• 제14권5호
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• pp.553-561
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• 2000

This paper presents a numerical model of multi phase flow of the mixtures of molten material-liquid-vapor, particularly in thermal nonequilibrium. It is a two-dimensional, transient, three-fluid model in Eulerian coordinates. The equations are solved numerically using the finite difference method that implicitly couples the rates of phase changes, momentum, and energy exchange to determine the pressure, density, and velocity fields. To examine the model's ability to predict an experimental data, calculations have been performed for tests of pouring hot particles and molten material into a water pool. The predictions show good agreement with the experimental data. It appears, however, that the interfacial heat transfer and breakup of molten material need improved models that can be applied to such high temperature, high pressure, multi phase flow conditions.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.165-170
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• 1998

Turbulent nonpremixed $H_2$-air jet flames are numerically investigated using the joint PDF model. The reaction progress variable is derived by assuming the radicals 0, H, and OH to be in partial equilibrium and additional species $HO_2$ and $H_2O_2$ in steady state. The model is extended to npnadiabatic flame by introducing additional variable for the transport of enthalpy and radiative source term is calculated using a local, geometry independent model. In terms of flame structure and NO formation, the predicted results are favorably agreed with experimental data. The effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

• 한국대기환경학회지
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• 제16권6호
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• pp.665-674
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• 2000

A major source of the hazardous waste generated is from chemical industries producing plastics, herbicides, pesticides and chlorinated solvents. All of these processes produce a class if hazardous waste termed the chlorinated hydrocarbons(CHCs), either directly or from undesirable side reactions. In this study, we investigated the destruction characteristics of hazardous waste through incineration. A nonequilibrium combustion model was used to describe the effect of the chemical kinetics due to the flame inhibition characteristics of $CCl_4$ which was used as the surrogate of hazardous waste. A parametric screening studies was made in a dump incinerator proposed in this study. The dump incinerator showed high $CCl_4$ DRE(Destruction and Removal Efficiency) as 5 nines. $CCl_4$/CH$_4$ ratio appeared to be most important in the destruction of $CCl_4$ through incineration.

• Progress in Superconductivity
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• 제4권2호
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• pp.104-108
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• 2003

We have measured the transport properties of $Bi_2$$Sr_2$$CaCu_2$$O_{8+d}$ (BSCCO) intrinsic Josephson junction mesa. Transport measurements with current flow along the c-axis, perpendicular to the layer of mesa showed multi-branch structures on the current-voltage characteristics. For single intrinsic junctions, the microwave radiation appears in the form of three different modes of oscillations, which include Josephson emission, nonequilibrium broad emission and sharp coherent microwave emission. Mutual phase interactions between two-mesas structures of BSCCO intrinsic Josephson junctions were studied. The results were explained within the framework of the Josephson plasma excitation model due to quasiparticle injection.n.

• International Journal of Aeronautical and Space Sciences
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• 제16권3호
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• pp.347-359
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• 2015

A method of describing the rovibrational energy transitions and coupled chemical reactions in the direct simulation Monte Carlo (DSMC) calculations is constructed for $H(^2S)+H_2(X^1{\Sigma}_g)$ and $He(^1S)+H_2(X^1{\Sigma}_g)$. First, the state-specific total cross sections for each rovibrational states are proposed to describe the state-resolved elastic collisions. The state-resolved method is constructed to describe the rotational-vibrational-translational (RVT) energy transitions and coupled chemical reactions by these state-specific total cross sections and the rovibrational state-to-state transition cross sections of bound-bound and bound-free transitions. The RVT energy transitions and coupled chemical reactions are calculated by the state-resolved method in various heat bath conditions without relying on a macroscopic properties and phenomenological models of the DSMC. In nonequilibrium heat bath calculations, the state-resolved method are validated with those of the master equation calculations and the existing shock-tube experimental data. In bound-free transitions, the parameters of the existing chemical reaction models of the DSMC are proposed through the calibrations in the thermochemical nonequilibrium conditions. When the bound-free transition component of the state-resolved method is replaced by the existing chemical reaction models, the same agreement can be obtained except total collision energy model.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.879-890
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• 2000

This study investigates the nonpremixed $H_2/CO$-air turbulent flames numerically. The turbulent combustion process is represented by a reaction progress variable model coupled with the presumed joint probability function. In the present study, the turbulent combustion model is applied to analyze the nonadiabatic flames by introducing additional variable in the transport equation of enthalpy and the radiative heat loss is calculated using a local, geometry independent model. Calculations are compared with experimental data in terms of temperature, and mass fraction of major species, radical, and NO. Numerical results indicate that the lower and higher fuel-jet velocity flames have the distinctly different flame structures and NO formation characteristics in the proximity of the outer core vortex zone. The present model correctly predicts the essential features of flame structure and the characteristics of NO formation in the bluff-body stabilized flames. The effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

• Bulletin of the Korean Chemical Society
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• 제26권12호
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• pp.1986-1990
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• 2005

We study the relaxation kinetics of reversible reactions of the type A + B $^\leftarrow_\rightarrow$ C + B by applying the manyparticle kernel theory, which we have developed to investigate many particle effects on general diffusioninfluenced reactions. It is shown that for the target model, where A and C molecules are immobile and their interconversion is induced by the encounter with the B molecules that are present in much excess, the manyparticle kernel theory gives a result that coincides with the known exact result.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.321-328
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• 2009

Free surface impinging jet on a moving plate, which is applicable to cooling of hot metals in a steel-making process, is investigated numerically by solving the Navier-Stokes equations in the liquid and gas phases. The free surface of liquid-gas interface is tracked by a level-set method which is improved by incorporating the ghost fluid approach based on a sharp-interface representation. The method is further improved by employing a nonequilibrium $\kappa-\varepsilon$ turbulence model including the effect of low Reynolds number. The computations are made to investigate the effects of the nozzle pitch, moving velocity of plate and jet velocity on the interfacial motion and the associated flow and temperature fields.