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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Combustion
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Journal DOI :
The Korean Society of Combustion
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Volume & Issues
Volume 9, Issue 4 - Dec 2004
Volume 9, Issue 3 - Sep 2004
Volume 9, Issue 2 - Jun 2004
Volume 9, Issue 1 - Mar 2004
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Activation Energy Asymptotics Revisited (I) - Quasisteady Extinction Conidtion of Diffusion Flames
Kim, Jong-Soo ;
Journal of the Korean Society of Combustion, volume 9, issue 2, 2004, Pages 1~9
Activation energy asymptotics (AEA) for Linan#s diffusion-flame regime is revisited in this paper. The main purpose of the paper is to carefully re-examine each AEA analysis step in order to clarify the some concepts that are often misunderstood among the ordinary practitioners of the AEA. Particular attention is focused on the different AEA regimes arising from the double limit of large Zel#dovich and Damkohler numbers. In addition, the expansion procedures are shown in detail and the method that the turning point condition, commonly known as the Linan#s extinction condition, is found is explained.
Unsteady Response of Counterflow Nonpremixed Flames Interacting with a Vortex
Oh, Chang-Bo ; Park, Jeong ; Lee, Chang-Eon ;
Journal of the Korean Society of Combustion, volume 9, issue 2, 2004, Pages 10~17
A two-dimensional direct numerical simulation is performed to investigate the flame structure of
counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman#s detailed reaction mechanism are adopted in this calculation. To quantify the strain on flame induced by a vortex, a scalar dissipation rate (SDR) is introduced. The results show that fuel-side and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex is extinguished at much larger SDR than steady flame. It is also found that air-side vortex extinguishes a flame more rapidly than fuel-side vortex. The unsteady effect induced by flame-vortex interaction does not lead to a transient OH overshoot of the maximum steady concentration observed in experiment, while
radical increases more than the maximum steady concentration with increasing SDR. In addition, it is seen that NO and
are not sensitive to the unsteady variation of SDR.
Simulation of a Diffusion Flame in Turbulent Mixing Layer by the Flame Hole Dynamics Model with Level-Set Method
Kim, Jun-Hong ; Chung, S.H. ; Ahn, K.Y. ; Kim, J.S. ;
Journal of the Korean Society of Combustion, volume 9, issue 2, 2004, Pages 18~29
Partial quenching structure of diffusion flames in a turbulent mixing layer has been investigated by the method of flame hole dynamics in oder to develope a prediction model for the phenomenon of turbulent flame lift off. The present study is specifically aimed to remedy the shortcoming of the stiff transition of the conditioned partial burning probability across the crossover condition by employing the level-set method which enables us to include the effect of finite flame edge propagation speed. In light of the level-set simulation results with two models for the edge propagation speed, the stabilizing conditions for turbulent lifted flame are suggested. The flame hole dynamics combined with the level-set method yields a temporally evolving turbulent extinction process and its partial quenching characteristics is compared with the results of the previous model employing the flame-hole random walk mapping based on three critical scalar dissipation rates. The probability to encounter reacting state, conditioned with scalar dissipation rate, demonstrated that the conditional probability has a rather gradual transition across the crossover scalar dissipation rate. Such a smooth transition is attributed to the finite response of the flame edge propagation.
A Study on the Combustion Characteristics of Coke and Anthracite in an Iron Ore Sintering Bed
Yang, Won ; Yang, Kwang-Heok ; Choi, Eung-Soo ; Ri, Deog-Won ; Kim, Sung-Man ; Choi, Sang-Min ;
Journal of the Korean Society of Combustion, volume 9, issue 2, 2004, Pages 30~37
Coal combustion in an iron ore sintering bed is a key parameter that determines quality of the sintered ores and productivity of the process. In this study, effects of the different types of coal - coke and anthracite - on the combustion in the iron ore sintering bed are investigated by modeling and experiment. Fuel characteristics of coke and anthracite are observed through a set of basic analysis and thermo-gravimetric analysis. Coke has a higher reactivity than anthracite due to the difference of surface area and density, and these characteristics are reflected in the 1-D unsteady simulation of the iron ore sintering bed. Calculation results show that different reactivity of the fuel can affect the bed combustion.
The evolution characteristics of incipient soot particles in ethylene/air inverse diffusion flame
Oh, Kwang-Chul ; Lee, Uen-Do ; Shin, Hyun-Dong ; Lee, Eui-Ju ;
Journal of the Korean Society of Combustion, volume 9, issue 2, 2004, Pages 38~44
The evolution of incipient soot particles has been examined by high resolution electron microscopy (HRTEM) and elemental analyzer in ethylene-air inverse diffusion flames. Laser Induced Incandescence(LII) and laser scattering methods were introduced for examining the soot volume fraction and morphological properties in combustion generated soot qualitatively. Soot particles, collected by thermophoretic sampling, were analyzed by using HRTEM to examine the nano structure of precursor particles. HRTEM micrographs apparently reveal a transformation of condensed phase of semitransparent tar-like material into precursor particles with relatively distinct boundary and crystalline which looks like regular layer structures. During this evolution histories, C/H analysis was also performed to estimate the chemical evolution of precursor particles. The changes of C/H ratio of soot particles with respect to residence time can be divided into two parts: one is a very slowly increasing regime where tar-like materials are transformed into precursor particles (inception process) the other is an increasing region with constant rate where surface growth affects the increase of C/H ratio dominantly (surface growth process). These results provide a clear picture of a transition to mature soot from precursor materials.