• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.555-558
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• 2008

The demand for a boiler with low NOx burner is increasing with the recent strict NOx regulation. Staged burner is a common low NOx burner to suppress the formation of thermal NOx by yielding local fuel rich and fuel lean condition. The staged burner gives fire with bigger frontal area and length compared with a conventional burner, which changes heat transfer characteristics in the combustion chamber. The heat transfer and exhaust gas characteristics has been studied in the present study for a 0.5 t/h class furnace type boiler adopting the staged burner. A numerical simulation has been conducted to clarify the detailed physics inside the combustion chamber.

• Journal of Advanced Marine Engineering and Technology
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• 제23권1호
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• pp.88-95
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• 1999

This study investigates the effects of different kind fuels on the flame structure by using the numerical simulation in triple flame made by a co-flowing fuels-air stream based on the elementary chemical reaction mechanism. Methane and Hydrogen were used as fuel for this study. In order to interpret the result of the study on numerical simulation Skeletal chemistry is employe as the elementary chemical reaction mechanism for methane Gutheil's as an offset ele-mentary chemical reaction mechanism for hydrogen. The result of this study is as follows. In com-parison between the apparent burning velocity change of triple flame and the one-dimensional pre-mixed flame hydrogen fuel flame is higher than methane fuel flame. The flame thrusts out for-ward in the down stream of the boundary between air-fuel mixture and air stream and a part of the flow is bent and forks out in this protruding flame so that a triple flame is originated.

• Journal of Advanced Marine Engineering and Technology
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• 제26권5호
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• pp.554-564
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• 2002

A newly designed combustion chamber of diesel engine with a modified piston crown was prepared for the purpose of investigation for reduction of NO emission. It was intended to realize 2-stage combustion that is to keep fuel rich condition during early stage of combustion and fuel lean condition during next stage. The engine was tested on various conditions concerning exhaust gas emissions especially about NO emission and simultaneously fuel consumption rate. It was found that the engine with 2-stage combustion type piston emits significantly low NO at various speed and torque compared with conventional engines, but it raised points at issue in CO and smoke emissions with fuel consumption rate. The increasing of injection pressure on 2 stage combustion type diesel engine affects on CO and smoke emission considerably to reduce but slightly on NO to increase. The effect of 2-stage combustion was better at low speed than at high speed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.422-427
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• 2000

Propagation characteristics of tribrachial flames have been investigated experimentally in both two-dimensional and axisymmetric counterflows. Mixture fraction gradient at stoichiometric location is controlled by varying equivalence ratios at the two nozzles, one of which maintains rich while the other lean premixture. Tribrachial flames propagating through these mixtures are investigated. The propagation speed of tribrachial flames in two-dimensional counterflow decreases with fuel concentration gradient and has much higher speed than the maximum speed predicted previously in two-dimensional mixing layers. From an analogy with premixed flame propagation, this excessively large propagation speed can be attributed to the tribrachial flame propagating with respect to burnt gas. Corresponding maximum speed in the limit of small mixture fraction gradient is estimated and extrapolated experimental results substantiate this limiting speed. As mixture fraction gradient approaches zero, a transition in propagation characteristics occurs, such that the propagation speed of tribrachial flame approaches stoichiometric laminar burning velocity with respect to burnt gas. Similar behavior has been obtained for tribrachial flames propagating in axisymmetric counterflow.

• 한국연소학회지
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• 제22권4호
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• pp.51-56
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• 2017

The decomposition of tetrafluoromethane has been investigated with the reaction mechanism proposed for freely propagating $CH_4/CF_4/O_2/N_2$ premixed flames on the oxygen enrichment. The factors affecting on the removal efficiency of tetrafluoromethane were analyzed. The increase in flame temperature due to oxygen enrichment has a great influence on the removal efficiency of tetrafluoromethane. At the same oxygen enrichment condition, the removal efficiency in the rich flame is higher than one in the lean flame. The increase of the F/H ratio leads to decrease the flame temperature and the removal efficiency of tetrafluoromethan is decreased at the flame temperature of 2600 K or lower, The elementary reactions that dominate the consumption of tetrafluoromethane are (R1) $CF_4+M=CF_3+F+M$ and (R2) $CF_4+H=CF_3+HF$. (R1) has the greatest effect on the consumption of tetrafluoromethane under the oxygen enhanced flames.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.156-167
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• 1996

The present work is a continuation of our previous study to investigate the effects of parameters such as equivalence ratio, hydrogen supplement rate and initial pressure on combustion characteristics in a disk-shaped constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The flames in near stoichiometric mixture of methane-air are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed to an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate. Also, flame is sluggishly propagated at increased initial pressure in combustion chamber. Volume fraction of burned gas and flame radius as the combustion characteristics are increased by increasing the hydrogen supplement rate, especially at the combustion middle period, but then are slowly increased by increasing the initial pressure.

• 한국연소학회지
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• 제19권1호
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• pp.11-16
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• 2014

Spherically expanding flames are used to measure flame speeds, which are derived the corresponding laminar flame speeds at zero stretch. Dimethyl Ether-Air mixtures at high pressure are studied over an extensive range of equivalence ratios. The classical shadowgraph technique is used to detect the reaction zone. In analytical methodology the optimization process using least mean squares is performed to extract the laminar flame speeds. It is seen that the laminar flame speed of DME-Air mixture with the increase of pressure decreases rapidly showing a similar trend to other hydrocarbon fuels. At pressure of 2 and 10 atm the experimental data from the present study agree well with results reported in the literature. Especially the laminar flame speeds at 2 atm are in good agreement with those calculated in numerical work over the full stoichiometric range. At elevated pressure of 12 atm the measured data are slightly slower at fuel lean condition and show close agreement at fuel rich condition when compared with the numerical results.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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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.

• Korean Chemical Engineering Research
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• 제61권4호
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• pp.555-560
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• 2023

기존 아민 수용액 기반 CO₂ 포집 공정을 산업적으로 적용할 경우 CO₂ 탈거 및 용매 재생에 따른 재생 에너지가 크다는 문제점을 갖고 있다. 본 논문은 CO₂에 대한 높은 흡수 용량과 함께 흡수제에 포함된 물의 조성을 낮춤으로써 재생 에너지를 저감할 수 있는 저수계 흡수제를 제안하였다. 이를 위해 본 연구에서는 디아민인 MAPA (3-methylaminopropylamine)와 함께 물의 일부를 대신하여 물에 비해 CO₂에 대한 물리적 용해도가 높고 비열이 낮은 NMP (N-methyl-2-pyrrolidone)를 흡수제에 도입하였다. 흡수제의 CO₂에 대한 흡수 용량(α_rich)과 순환 흡수 용량(Δα) 및 흡수 속도는 충전탑을 이용하여 측정하였다. 2.5M의 MAPA를 포함한 흡수제를 사용했을 경우 NMP가 10 wt% 포함된 경우에 최대 순환 흡수 용량을 얻을 수 있었다. 총괄물질전달 계수는 NMP의 농도가 증가함에 따라 증가하였다. 그러나 0.5보다 더 높은 CO₂ 로딩 값에서는 NMP의 농도 증가에 따른 물질전달 계수의 증가 폭이 줄어들었다. lean 로딩 값이 낮은 경우에는 점성에 의한 물질전달 저항이 낮아서 NMP 첨가에 따라 총괄 물질전달 계수가 증가하나 로딩 값이 증가함에 따라 흡수제의 점도가 증가하면서 CO₂와 MAPA의 확산도가 낮아지며 이에 따라 총괄 물질전달계수가 급격히 감소하였다.

• KEPCO Journal on Electric Power and Energy
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• 제4권1호
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• pp.33-38
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• 2018

This study applied upgrades to the processes of a 10 MW wet amine $CO_2$ capture pilot plant and conducted performance evaluation. The 10 MW $CO_2$ Capture Pilot Plant is a facility that applies 1/50 of the combustion flue gas produced from a 500 MW coal-fired power plant, and is capable of capturing up to 200 tons of $CO_2$. This study aimed to quantitatively measure efficiency improvements of post-combustion $CO_2$ capture facilities resulting from process upgrades to propose reliable data for the first time in Korea. The key components of the process upgrades involve absorber intercooling, lean/rich amine exchanger efficiency improvements, reboiler steam TVR (Thermal Vapor Recompression), and lean amine MVR (Mechanical Vapor Recompression). The components were sequentially applied to test the energy reduction effect of each component. In addition, the performance evaluation was conducted with the absorber $CO_2$ removal efficiency maintained at the performance evaluation standard value proposed by the IEA-GHG ($CO_2$ removal rate: 90%). The absorbent used in the study was the highly efficient KoSol-5 that was developed by KEPCO (Korea Electric Power Corporation). From the performance evaluation results, it was found that the steam consumption (regeneration energy) for the regeneration of the absorbent decreased by $0.38GJ/tonCO_2$ after applying the process upgrades: from $2.93GJ/ton\;CO_2$ to $2.55GJ/tonCO_2$. This study confirmed the excellent performance of the post-combustion wet $CO_2$ capture process developed by KEPCO Research Institute (KEPRI) within KEPCO, and the process upgrades validated in this study are expected to substantially reduce $CO_2$ capture costs when applied in demonstration $CO_2$ capture plants.