• Journal of the Korean Society of Combustion
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• v.23 no.1
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• pp.21-27
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• 2018

The effect of swirl flow structures on combustion dynamics of two interacting, lean-premixed flames was experimentally investigated, with a particular emphasis on swirl numbers and swirl rotational directions. Our results show that the amplitude of limit cycle oscillations is very sensitive to the combination of swirl numbers and rotational directions, while the instability frequency remains nearly unchanged. The counter-rotating cases show significantly lower pressure perturbations, and this behavior appears to be related to the formation of compact interacting zone with higher heat release rate, indicating the presence of increased flame surface wrinkling caused by intense turbulence.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.81-89
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• 2002

The autoignition and subsequent flame propagation of initially nonpremixed turbulent system have been numerically analyzed. The unsteady flamelet modeling based on the RIF (representative interactive flamelet) concept has been employed to account for the influences of turbulence on these essentially transient combustion processes. In this RIF approach, the partially premixed burning, diffusive combustion and formation of pollutants(NOx, soot) can be consistently modeled by utilizing the comprehensive chemical mechanism. To treat the spatially distributed inhomogeneity of scalar dissipation rate, the multiple RIFs are employed in the framework of EPFM(Eulerian particle flamelet model) approach. Computations are made for the various initial conditions of pressure, temperature, and fuel composition. The present turbulent combustion model reasonably well predicts the essential features of autoignition process in the transient gaseous fuel jets injected into high pressure and temperature environment.

• 한국연소학회:학술대회논문집
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• 2000.05a
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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.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.15-21
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• 2010

The transported probability density function(PDF) model has been applied to simulate the turbulent nonpremixed piloted jet flame. To realistically account for the mixture fraction PDF informations on the turbulent non-premixed jet flame, the present Lagrangian PDF transport approach is based on the joint velocity-composition-turbulence frequency PDF formulation. The fluctuating velocity of stochastic fields is modeled by simplified Langevin model(SLM), turbulence frequency of stochastic fields is modeled by Jayesh-Pope model and effects of molecular diffusion are represented by the interaction by exchange with the mean (IEM) mixing model. To validate the present approach, the numerical results obtained by the joint velocity-composition-turbulence frequency PDF model are compared with experimental data in terms of the unconditional and conditional means of mixture fraction, temperature and species and PDFs.

• Journal of the Korean Society of Safety
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• v.23 no.4
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• pp.30-35
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• 2008

The present study has been conducted to examine the effect of grid resolution on the predicted results for electric cable fire using pyrolysis model in FDS(Fire Dynamics Simulator, version 5). The grid independent test for different grid resolutions has been performed for a PE coating cable and the grid resolution is defined by the non-dimensional characteristic length of fire and mean grid size. The calculated maximum heat release rate and mean flame spread rate were almost constant for higher grid resolution of 20${\sim}$25 and the computing time for the grid resolution takes approximately 20hours to solve flame propagation with pyrolysis model. The geometrical simplification of a electric cable dose not greatly affect on the maximum heat release rate and flame spread rate and the rectangular approximation of cable shape gives acceptable result comparing with the round cable with stepwise grid.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.335-338
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• 2012

The present study focuses mainly on modeling the ordinary diffusion flux of species. According to CHEMKIN, both the mixture-averaged approach, Fick's formula, and the full multicomponent approach are implemented in the framework of opensource OpenFOAM. Also the Stefan-Maxwell approach is coded and validated together against measurements of laminar hydrogen jet flame. In the case of viscosity and conductivity of mixture, the mixture-averaged approach is applied and thermal diffusion is not considered in this work. Results show that there are no distinct deviations in three different approaches of diffusion of species in the present hydrogen flame condition.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.3
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• pp.74-78
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• 2003

The structural property of phenolic and non-phenolic lignin has an effect on the reaction rate of lignin by oxygen and chlorine dioxide respectively. Moreover, the undesirable degradation of cellulose followed by lignin degradation is influenced by chemical charge and reaction time. In this paper, several lignin model compounds were used to illuminate the interaction of oxygen and chlorine dioxide by varying the position of O and D(OD, DO, ODO and DOD), and gas chromatography method was used to investigate the degradation of lignin by determining the content of methoxyl groups in lignin. It was shown that structural properties of lignin models were more influential on the degradation and demethylation of lignin than the above combination. Combination of oxygen and chlorine dioxide, however, was more effective in degradation of lignin than only one stage, and three stages than two stages.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.332-335
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• 2008

The purpose of this study is analysis of flow field where is around of injector of supersonic combustor which is bluff-body stabilized flame and hyper-mixer type of supersonic combustor injector by using hydrogen or hydrocarbon fuel. Various schemes are evaluated to supersonic backward step flow filed with massive separation region in validation step. Compounded scheme of 5th-order TVD-MUSCL, Roe FDS, S-A DES/DDES has a good performance in base and base-bleed flow.

• Journal of ILASS-Korea
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• v.6 no.3
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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.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.25-27
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• 2009

This paper presents the stereoscopic conversion of flame images. The stereoscopic conversion is a technology that generates left and right images from a monoscopic image. Even though many conversion methods have been introduced and commercialized so far, the processing of flame images is relatively few. Such conventional methods are effectively used either real-time or off-line. However, the application of such schemes to special-effect images such as flame is hard to be applied. The proposed method is designed to convert a flame image into a stereoscopic image. Depth map of flame regions are produced based on the analysis of color models of flames. Experimental results tested on diverse flame image sets validates the effectiveness of the proposed method.