• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.63-71
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• 2001

The objective of this work is to elucidate the details of two key factors dominating the droplet buring behavior in sprays : droplet-droplet interaction and convective flow. The combustion of a one-dimensional linear droplet array with a convective flow has been studied. A one-step, second order model was employed to simulate the chemical reaction in the combustion process. Results for droplet arrays burning at two Reynolds numbers, 50 and 100, two horizontal droplet spacings, 5 and 11 radii, and two vertical droplet spacing, 2 and 4 radii, were obtained. The results indicate the droplet burning behavior is affected by Reynolds number, droplet-droplet spacing, and the relative location of droplets in the array. Droplet-droplet interaction was found to be strong for arrays with smaller droplet spacing.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.53-56
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• 2015

A combined experimental and numerical study has been conducted to investigate the downstream interaction between simulated SNG-air premixed flames in fuel composition of 91% $CH_4$ + 6% $C_3H_8$ + 3% $H_2$. In this study, the effects of fuel molar concentration(lean-rich) and strain rate($a_g$) were major parameters. A main focus is to investigate flames behavior and chemical interaction at flames downstream. The numerical results were calculated by OPPDIF application. The reaction mechanism adopted was USC-II model including C3 reaction.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.303-306
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• 2011

An experimental study has been conducted to investigate the effects of an ultrasonic standing-wave field to the behavior of methane/air premixed flame. Visualization technique utilizing the schlieren method was employed for the observation of premixed flame behavior. The shape of flame front and local flame velocity were measured according to the variation of reactants pressure and chamber opening/closing condition. The flame front was distorted and severely deformed to a lotus-type flame by the interaction of ultrasonic standing-wave and the reflection wave coming from an end wall of reactor.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.70-77
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• 2012

Experimental investigations were performed to examine the characteristics of propagating flame fronts around multiple bars within a rectangular chamber. The explosion chamber is 400 mm in height, $700{\times}700mm^2$ in cross-section and has a large top-venting area, $A_v$, of $700{\times}210mm^2$. This results in a value of 0.44 for $A_v/V^{2/3}$ and a L/D value of 0.57. The multiple obstacles of length 700 mm with a blockage ratio of 30 % were placed within the chamber. Temporally resolved flame front images were recorded by a high speed video camera to investigate the interaction between the propagating flame and the obstacles. Results showed that the flame propagation speeds before the flame impinges onto the obstacle almost equal to the laminar burning velocity. As the propagating flame impinged on the obstacle, the central region of flame began to become concave, this resulted in the flame deceleration in the region. As the flame interacted with the modified flow filed generated behind the central obstacle, the probability density functions(PDFs) of the local flame displacement speed were extensively distributed toward higher speeds.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.1-11
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• 1997

The soot and OH radical distributions have been experimentally studied in ethylene and propane laminar diffusion flames. The integrated soot volume fraction was measured along the centerline of a flame using a laser light extinction method. Planar laser light scattering and PLIF techniques are employed for the soot and OH radical distribution measurements utilizing Nd:YAG laser and OPO, FDO system. The concentration of OH radical is rapidly decreased at the edge of sooting region, which implies the importance of OH radical species on the soot oxidation process. For ethylene flames, the addition of air in fuel moves the OH radical distribution towards the center line of a flame at the soot oxidation region, while the concentration of OH radical remains relatively high at the soot formation region. The interaction between soot particles and OH radicals becomes more active with fuel-air at the soot oxidation region. For propane flames, however, any indication of the increased interaction between soot particles and OH radicals with fuel-air was not noticed.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.131-139
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• 1999

A Numerical Analysis of NOx production in Hydrogen-Air flame is performed using the quasi-laminar reaction modelling. As results, in low global strain rate region, $U_F/D_F\;{\leq}\;50,000$, the quasi-laminar reaction modelling reproduces the experimentally observed EINOx half power scaling that the ratio of EINOx and flame residence time, $L_f^3(D_F^2U_F)$, is proportional to the square root of global strain rate. Thus, it suggests that turbulence-chemistry interaction has a minor impact on the trend of NOx production in low global strain rate region. However, the quasi-laminar reaction modelling predicts the higher temperature and NOx than experimentally observed. This overprediction may be due to the lack of radiation and quasi-laminar reaction modelling.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.75-82
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• 2004

The conditional moment closure(CMC) model has been implemented in context with the unstructured-grid finite-volume method which efficiently handle the physically and geometrically complex turbulent reacting flows. The validation cases include a turbulent nonpremixed $CO/H_2/N_2$ Jet flame and a turbulent nonpremixed $H_2/CO$ flame stabilized on an axisymmetric bluff-body burner. In terms of mean flame field, minor species and NO formation, numerical results has the overall agreement with expermental data. The detailed discussion has been made for the turbulence-chemistry interaction and NOx formation characteristics as well as the comparative performance for CMC and flamelet model.

• Journal of the Korean Society of Combustion
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• v.14 no.2
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• pp.10-17
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• 2009

The present study numerically investigate the effects of the Syngas chemical kinetics on the basic flame properties and the structure of the Syngas nonpremixed flames. In order to realistically represent the turbulencechemistry interaction and the spatial inhomogeneity of scalar dissipation rate, the Eulerian Particle Flamelet Model (EPFM) with multiple flamelets has been applied to simulate the combustion processes and NOx formation in the syngas turbulent nonpremixed flames. Validation cases include the Syngas turbulent nonpremixed jet and swirling flames. Based on numerical results, the detailed discussion has been made for the effects of the chemical kinetics, the flame structure, and NOx formation characteristics in the turbulent Syngas nonpremixed flames.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.289-291
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• 2012

The present study numerically investigate detailed flame structure of the Syngas diffusion flames. In order to realistically represent the turbulence-chemistry interaction and the spatial inhomogeneity of scalar dissipation rate, the Eulerian Particle Flamelet Model(EPFM) with multiple flamelets has been applied to simulate the combustion processes and NOx formation in the syngas turbulent nonpremixed flames. And level-set approach is also utilized to account for the partially premixing effect at fuel and oxidizer injector in KEPRI nonpremixed combustor. Based on numerical results, the detailed discussion has been made for the precise structure and NOx formation characteristics of the turbulent syngas nonpremixed flames.

• Journal of the Korean Society of Combustion
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• v.21 no.2
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• pp.22-28
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• 2016

High efficient and environment friendly combustion technologies are used to be operated an extreme condition, which results in unintended flame instability such as extinction and oscillation. The use of electromagnetic energy is one of methods to enhance the combustion stability and a microwave as electromagnetic wave is receiving increased attention recently because of its high performance and low-cost system. In this study, an experiment was performed with jet diffusion flames induced by microwave. Micro jet was introduced to simulate the high velocity of industrial combustor. The results show that micro jet flames had three different modes with increasing oxidizer velocity; attached yellow flame, lifted flame, and lifted partially premixed flame. As a microwave was induced to flames, the overall flame stability and blowout limit were extended with the higher microwave power. Especially the interaction between a flame and a microwave was shown clearly in the partially premixed flame, in which the lift-off height decreased and NOx emission measured in post flame region increased with increasing microwave power. It might be attributed to increase of reactivity due to the abundance of radical pool and the enhanced absorption to thermal energy.