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Sung, Yonmo,Choi, Gyungmin Elsevier 2016 Fuel Vol.174 No.-
<P><B>Abstract</B></P> <P>Optical non-intrusive measurements are performed to a 10kW<SUB>th</SUB> laboratory-scale dual swirl pulverized coal combustion burner in order to elucidate the behaviors of internal recirculation zone (IRZ) and heat release region. The pulverized coal flame is operated with four different swirl combinations: co-swirling (low- and high-swirl) and counter-swirling (low- and high-swirl). The flow field is measured using particle image velocimetry (PIV). The IRZ area increases for the high-swirl conditions than that in the low-swirl conditions. With changing from co- to counter-swirl combination, the IRZ appearance changes from a heart- to an elongate-shape IRZ because double stagnation points for the co-swirling flames merges to one stagnation point for the counter-swirling flames. For the co-swirling conditions, a tube-type vortex is detected at the end of the IRZ near the double stagnation points. However, it is not present in the counter-swirling conditions. From two-color pyrometry, the overall temperature in the high-swirl flames is lower than the low-swirl flames. For the counter-swirling flames, higher temperature is observed due to the better mixing, which allows for a more intense combustion reaction of pulverized coal particles. Flame color measurements (OH and CH chemiluminescence band light emission) shows that the devolatilization of coal particles is observed at more upstream region comparing with the heat release reaction for volatile gas combustion. For the high-swirl flames, the CH<SUP>∗</SUP> band intensity for heat release decreases, however its overall dimension increases. For the counter-swirling flames, the higher heat release is observed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dual swirl-stabilized pulverized coal flames are evaluated with co- and counter-swirl. </LI> <LI> Behavior of internal recirculation zone and stagnation point is revealed using the PIV. </LI> <LI> Heat release characteristics are investigated using the flame color measurements. </LI> </UL> </P>
Sung, Yonmo,Charalampous, Georgios,Hardalupas, Yannis,Choi, Gyungmin Elsevier 2017 Proceedings of the Combustion Institute Vol.36 No.2
<P><B>Abstract</B></P> <P>The influence of turbulence on the minimum ignition energy (MIE) and ignited flame characteristics is investigated for pulsed methane diffusion jets ignited by laser-induced plasma. The methane jet is injected in a volume of homogeneous and isotropic air turbulence without mean flow, with the level of turbulence being controlled independently. The study is carried out for a range of fuel jet (<I>Re</I> <SUB>jet</SUB>) Reynolds number, namely 1000, 2000, and 3000, and a range of turbulent (<I>Re</I> <SUB>λ</SUB>) Reynolds number, namely 0–207. The results show that the position of the maximum intensity of flame emission was randomly scattered due to the fact that the ignited flame is deflected from the nozzle axis by the turbulent velocity fluctuations. The effect is more profound at higher <I>Re</I> <SUB>jet</SUB>. The value of the MIE, determined according to 50% ignitibility of mixture, increases by a factor of 2 for an increase of <I>Re</I> <SUB>λ</SUB> from 0 to 207 and by a factor of 5 for an increase of <I>Re</I> <SUB>jet</SUB> from 1000 to 3000. Two trends are observed on MIE with <I>Re</I> <SUB>λ</SUB>. For low <I>Re</I> <SUB>λ</SUB>, MIE is independent of <I>Re</I> <SUB>λ</SUB>. Past a critical value of <I>Re</I> <SUB>λ</SUB>, MIE increases as a linear function of <I>Re</I> <SUB>λ</SUB>. This transition occurs at critical values of <I>Re</I> <SUB>λ,c</SUB> = 158, 197 and 202 for <I>Re</I> <SUB>jet</SUB>= 1000, 2000 and 3000, respectively. The mean value of MIE for ignition before and after transition is a linear function of <I>Re</I> <SUB>jet</SUB>. The difference between the mean value of MIE before transition and after transition is around 5mJ for all considered <I>Re</I> <SUB>jet</SUB>.</P>
역청탄과 아역청탄 혼합연소조건에서 혼소율이 순산소 연소특성에 미치는 영향
성연모(Yonmo Sung),문철언(Cheoreon Moon),안성율(Seongyool Ahn),안재우(Jaewoo An),나종문(Jongmoon Na),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41
This study focuses on the combustion characteristics of blended coals with bituminous and sub-bituminous coals under air and oxy-fuel combustion conditions. The effects of oxygen concentration and blending ratio on the combustion characteristics were experimentally investigated using a thermogravimetric analyser(TGA). Characteristic temperatures including ignition, burnout temperature and activation energy were determined from TG and DTG combustion profiles. As oxygen concentration increased and the presence of sub-bituminous coal, characteristic temperatures and activation energy decreased. The ignitability, reactivity and kinetics have all been greatly improved under oxy-fuel combustion conditions. Based on this, co-firing with bituminous and sub-bituminous coals under oxy-fuel combustion conditions may be suggested as an alternative method to the fuel flexibility and cost-effective power production with carbon capture and sequestration.
Effect of static mixer geometry on flow mixing and pressure drop in marine SCR applications
Park, Taewha,Sung, Yonmo,Kim, Taekyung,Lee, Inwon,Choi, Gyungmin,Kim, Duckjool The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.1
Flow mixing and pressure drop characteristics for marine selective catalytic reduction applications were investigated numerically to develop an efficient static mixer. Two different mixers, line- and swirl-type, were considered. The effect of vane angles on the relative intensity, uniformity index, and pressure drop was investigated in a swirl-type mixer; these parameters are dramatically affected by the mixer geometry. The presence of a mixer, regardless of the mixer type, led to an improvement of approximately 20% in the mixing performance behind the mixer in comparison to not having a mixer. In particular, there was a tradeoff relationship between the uniformity and the pressure drop. Considering the mixing performance and the pressure drop, the swirl-type mixer was more suitable than the line-type mixer in this study.
Numerical analysis of NO<sub>x</sub> reduction for compact design in marine urea-SCR system
Choi, Cheolyong,Sung, Yonmo,Choi, Gyung Min,Kim, Duck Jool The Society of Naval Architects of Korea 2015 International Journal of Naval Architecture and Oc Vol.7 No.6
In order to design a compact urea selective catalytic reduction system, numerical simulation was conducted by computational fluid dynamics tool. A swirl type static mixer and a mixing chamber were considered as mixing units in the system. It had great influence on flow characteristics and urea decomposition into ammonia. The mixer caused flow recirculation and high level of turbulence intensity, and the chamber increased residence time of urea-water-solution injected. Because of those effects, reaction rates of urea decomposition were enhanced in the region. When those mixing units were combined, it showed the maximum because the recirculation zone was significantly developed. $NH_3$ conversion was maximized in the zone due to widely distributed turbulence intensity and high value of uniformity index. It caused improvement of $NO_x$ reduction efficiency of the system. It was possible to reduce 55% length of the chamber and connecting pipe without decrease of $NO_x$ reduction efficiency.
Choi, Minsung,Sung, Yonmo,Won, Myungjun,Park, Yeseul,Kim, Minkuk,Choi, Gyungmin,Kim, Duckjool Elsevier 2017 Journal of industrial and engineering chemistry Vol.48 No.-
<P><B>Abstract</B></P> <P>Numerical analysis of lean-premixed flames is utilized to investigate the correlation between turbulence and combustion, fuel–air mixing, and NO<SUB>x</SUB> emission using three types of micro gas turbine combustors. Swirl flows generating vortex breakdown and flow recirculation contributing to mixing uniformity are improved by interaction of burners. Mixing plays an important role in flame dynamics and NO<SUB>x</SUB> emission by means of the unmixedness parameter. To discuss the correlation between flame characteristics and vorticity structures, progress variable <I>c</I> is introduced. The flame stability is enhanced by ring-shaped, large-scale vorticity structures, and air–fuel mixing is increased by momentum and kinetic energy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We study a numerical analysis of a lean-premixed flames in a micro gas turbine combustor. </LI> <LI> The large eddy simulation model is adopted to predict unsteady turbulent motions of methane-air premixed flames. </LI> <LI> The effect of the interaction of the between burners has a larger impact on the mixing process. </LI> <LI> A lower local equivalence ratio of the between burners produces a lower temperature distribution, reducing thermal NO<SUB>x</SUB> formation. </LI> <LI> The flame stability is enhanced by ring-shaped large scale coherent vorticity structures. </LI> <LI> Air–fuel mixing is also increased by strong momentum and high kinetic energy with low NO<SUB>x</SUB> emission. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
15kW급 미분탄 연소로내에서 바이오매스 혼소율 변화에 따른 연소 특성 비교
이상민(Sangmin Lee),성연모(Yonmo Sung),최민성(Minsung Choi),문철언(Cheoreon Moon),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11
This study focused on the effect of the biomass blended ratio on air-staged pulverized coal furnace. The hybrid NOx reduction technology between fuel blending and air staging has been applied in an air-staged pulverized coal fired furnace. The results indicated that co-firing biomass with coal could reduce NOx emissions in an air-staged combustion. In addition, carbon burnout and flame temperature increased under the air-staged condition. A dominant synergistic effect on NOx reduction and carbon burnout was observed when biomass co-firing with coal was applied in air staged combustion.
미분탄 이중 스월화염에서 스월강도 및 석탄 입경 변화 영향 연구
최민성(Minsung Choi),성연모(Yonmo Sung),이상민(Sangmin Lee),문철언(Cheoreon Moon),최경민(Gyungmin Choi),김덕줄(Duckjool Kim) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11
The present work focuses on the analysis of the pulverized coal combustion aerodynamics of the dual swirl burner by the control of the swirl-modes such as the outer swirl intensity (OSI). The detailed structure of pulverized coal swirling flames with swirl-mode was studied experimentally by particle image velocimetry and local flame colors based on OH<SUP>*</SUP>, CH<SUP>*</SUP>, and C₂<SUP>*</SUP> radicals. For all co-swirling conditions, the internal recirculation zone (IRZ) was observed near the inner shear layer with respect to the processing vortex core structure. Furthermore, a co-rotating vortex in the outer shear layer and the exhaust tube vortex (ETV) along the central axis were observed. The intensity of CH<SUP>*</SUP> signal was higher with small coal particle size, conversely, the size of the distribution of the CH<SUP>*</SUP> signal becomes larger. Therefore, the control of the aerodynamics with changing swirl intensities may play an important role in improving both environmental and combustion performances.
미분탄 스월버너에서 PKS와 석탄 혼소가 화염 구조에 미치는 영향
신민호(Minho Shin),성연모(Yonmo Sung),최민성(Minsung Choi),이광수(Gwangsu Lee),최경민(Minsung Choi),김덕줄(Duckjool Kim) 한국연소학회 2016 한국연소학회지 Vol.21 No.4
Flame structure of co-firing coal and palm kernel shell (PKS) was investigated in a pulverized coal swirl burner by particle image velocimetry (PIV). The pulverized coal swirl flame is operated with a PKS blending ratio of 10%, 20%, and 30%. For all operating conditions, flame structures such as internal recirculation zone (IRZ), outer recirculation zone (ORZ), and exhaust tube vortex (ETV) were observed. In the center of flame, the strong velocity gradient is occurred at the stagnation point where the volatile gas combustion actively takes place and the acceleration is increased with higher PKS blending ratio. OH radical shows the burned gas region at the stagnation point and shear layer between IRZ and ORZ. In addition, OH radical intensity increases for a co-firing condition because of high volatile matter from PKS. Because the volatile gas combustion takes place at lower temperature, co-firing condition (more than 20%) leads to oxygen deficiency and reduces the combustibility of coal particle near the burner. Therefore, increasing PKS blending ratio leads to higher OH radical intensity and lower temperature.