• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.169-174
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• 2004

The NOx emission characteristics with oxygen enrichment in nonpremixed counterflow and coflow jet flame of $CH_4$ fuel have been investigated numerically. A small amount of nitrogen is included in oxygen-enriched combustion, in order to consider the inevitable $N_2$ contamination by air infiltration. The results show that the initial increase of NO with increasing oxygen enrichment is due to increasing temperature and residence time, while its subsequent decrease above 75% oxygen is due to decreasing the consumption rate of nitrogen. When oxygen addition exceeds 30%, Thermal NO gradually becomes the dominant production pathway and Prompt NO becomes negative pathway for net NO production rate. It is also seen that Thermal NO plays an important role in NO reduction when strain rate increase in oxygen-enriched combustion. Finally, the results of EINOx with oxygen enrichment in coflow jet flame show the similar profile with those of conterflow flame. It is confirmed that, with leakage of 1% nitrogen in the oxidizer stream, the corresponding EINOx is eight times of that emitted from regular $CH_4$/Air flame.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.845-851
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• 2003

The purpose of this experimental study is to investigate the quantitative pollutants reduction by oxygen enrichment and induced air effect in venturi type after-burner. For this purpose, CO, $CO_2$, $O_2$. and HC concentrations were measured before and after the after-burner by changing the Oxygen flow rate and area ratio which is defined as the ratio of air inducing area divided by total area. As results of this study, when the area ratio were increased, the emission reduction effect was increased even less oxygen flow rate. In that case when oxygen was injected too little, the pollutants were increased.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1128-1133
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• 2004

A comprehensive experimental and numerical study has been conducted to understand the influence of $CH_{3}Cl$ addition on $CH_{4}/O_{2}/N_{2}$ premixed flames under the oxygen enrichment. The laminar flame speeds of $CH_{4}/CH_{3}Cl/O_{2}/N_{2}$ premixed flames at room temperature and atmospheric pressure are experimentally measured using Bunsen nozzle flame technique, varying the amount of $CH_{3}Cl$ in the fuel, the equivalence ratio of the unburned mixture, and the level of the oxygen enrichment. The flame speeds predicted by a detailed chemical kinetic mechanism employed are found to be in excellent agreement with those deduced from experiments. As $CH_{3}Cl$ addition is increased temperature at the postflame is not almost varied but the heat release rate and $EI_{NO}$ are decreased. The function of $CH_{3}Cl$ as inhibitor on hydrocarbon flames becomes weakened as the level of the oxygen enrichment is increased from 0.21 to 0.5.

• 대한기계학회논문집B
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• 제29권2호
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• pp.255-262
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• 2005

A comprehensive experimental and numerical study has been conducted to understand the influence of $CH_{3}Cl$ addition on $CH_4/O_2/N_2$ premixed flames under the oxygen enrichment. The laminar flame speeds of $CH_4/CH_{3}Cl/O_2/N_2$ premixed flames at room temperature and atmospheric pressure are experimentally measured using Bunsen nozzle flame technique, varying the amount of $CH_{3}Cl$ in the fuel, the equivalence ratio of the unburned mixture, and the level of the oxygen enrichment. The flame speeds predicted by a detailed chemical kinetic mechanism employed are found to be in excellent agreement with those deduced from experiments. Even though the molar amount of $CH_{3}Cl$ in a methane flame is increased, temperature at the postflame is not significantly varied, but the calculated heat release rate and emission index of NO are largely decreased for the oxygen enhanced flame. The function of $CH_{3}Cl$ as inhibitor on hydrocarbon flames becomes weakened as the level of the oxygen enrichment is increased from 0.21 to 0.5.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.332-337
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• 2003

Oxygen-enriched non-premixed flame characteristics was investigated numerically with variation of dilution methods, which are Flue gas recirculation(FGR) and fuel injection recirculation(FIR). In order to compare flamelets in various oxygen-enrichment conditions reasonably, the adiabatic flame temperature and Damkoller number was held fixed by modulating amount of diluents to fuel and oxidizer stream and by varying global strain rate of flame respectively. Also modified GRI 3.0 reaction mechanism was utilized, which was able to predict oxygen-enriched methane flame correctly. Fundamental flame characteristics such as structure, heat release rate and extinction with FGR and FIR were compared in various oxygen enrichment conditions.

• 한국가스학회지
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• 제11권4호
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• pp.17-22
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• 2007

비예혼합 대향류화염에서 산소부화에 따른 NOx 생성특성에 관한 수치해석이 수행되었다. 순산소의 연소과정에서 공기침투에 의한 부득이한 질소 유입의 상황을 체계적으로 고려하기 위하여, 산화제의 $O_2$는 체적비 21%에서 100%까지 변화되었다. 결과적으로 NO 배출지수$(EI_{NO})$는 산소부화율 75%까지 증가하다가 급격히 감소하는 경향을 보여준다. 이러한 경향은 화염온도, 화염두께 및 체류시간 보다는 NOx 생성과 관련된 $N_2$ 소모율 변화에 의해 설명될 수 있음을 확인하였으며, 특히 N+NO=$N_2+O$ 반응이 가장 크게 기여함을 알 수 있었다.

• 대한기계학회논문집B
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• 제28권2호
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• pp.207-214
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• 2004

The burning velocities of conventional and oxygen-enriched methane flame in various equivalence ratio were determined by experiments. The validity of existing reaction mechanisms was examined in oxygen-enriched flame on the basis of the experiment results. Modified reaction mechanism is suggested, which was able to predict burning velocity of oxygen enriched flame as well as methane-air flame. Complementary study on reaction mechanisms shows the following results : Present experiment data were found to be more reliable in comparison with existing ones in a oxygen-enrichment condition. It was found that some modification in existing reaction mechanisms is necessary, since discrepancy between measurements and predictions is increasing with oxygen enrichment ratio. The sensitivity analysis was performed to discriminate the dominantly affecting reactions on the burning velocity in various oxygen enrichment and equivalence ratio. A modified GRI 3.0 reaction mechanism based on our experiment results was suggested, in which reaction rate coefficients of (R38) H+O$_2$<=>O+OH in GRI 3.0 reaction mechanisms were corrected based on sensitivity analysis results. This mechanism showed a good agreement in predicting the burning velocity and number density of NO in oxygen-enriched flame and would provide proper reaction information of oxygen-enriched flame at this stage.

• 한국수소및신에너지학회논문집
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• 제21권1호
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• pp.42-49
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• 2010

Increasing environmental concerns regarding the use of fossil fuels and global wanning have prompted researcher to investigate alternative fuels. The purpose of this study is to investigate the syngas production by biogas reforming using a compression spark ignition engine. The parametric screening studies were carried out according to the variations of oxygen enrichment rate, biogas $CO_2$ ratio, intake gas temperature, and engine revolution. When the oxygen enrichment rate and input gas temperature increased, hydrogen and carbon monoxide were increased. But the biogas $CO_2$ ratio and engine revolution increased, the syngas were reduced. For the reforming of methane 100% only, generation of hydrogen and carbon monoxide was 58% and 17%, respectively. However when the biogas $CO_2$ ratio was 40%, hydrogen and carbon monoxide concentration were about 20% each.

• 천문학회보
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• 제35권2호
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• pp.29.2-29.2
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• 2010

We present elemental abundances of 412 blue compact dwarf galaxies (BCDs) at z=0.2~0.5 using the Sloan Digital Sky Survey (SDSS) DR7. The gas-phase nitrogen to oxygen abundance ratios (N/O) of sample galaxies increase as the oxygen to hydrogen abundance ratios (O/H) decrease. This indicates that the nitrogen is more enriched than the oxygen. We found that there is a noticeable distinction between the merger candidates and the isolated galaxies. Merging candidates show more enrichment of nitrogen abundance compared to isolated galaxies. On the other hand, neon and oxygen abundances for merging candidates are slightly lower than the isolated systems. We discuss the main cause of these trends with internal mixing and mass loss by fast rotation of young massive stars. We also discuss the environmental effect to the relation between specific star formation rate and galaxy mass.

• 대한기계학회논문집B
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• 제35권8호
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• pp.839-845
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• 2011

산소부화 조건의 $CH_4/O_2/N_2$ 화염에서 트리플루오르메탄의 영향을 조사하기 위해 1기압에서 자유롭게 전파하는 예혼합 화염에 대한 수치해석을 수행하였다. 트리플루오르메탄은 화염속도 감소에 기여하며, 감소의 크기는 화학적 효과보다 물리적 효과에 의해 더 크다. 트리플루오르메탄은 산소부화된 $CH_4/O_2/N_2$ 화염에서 더 많이 첨가되고 소비될 수 있다. 트리플루오르메탄은 주로 $CF_3{\rightarrow}CF_2{\rightarrow}CF{\rightarrow}CF:O{\rightarrow}CO$을 통해 분해되고, 산소부화 화염에서 $CHF_3+M{\rightarrow}CF_2+HF+M$이 중요한 역할을 한다. 억제제가 산소 부화 화염에 첨가함에 따라 활성기 최대 농도의 위치는 상대적으로 낮은 온도로 이동하고, OH의 순생성률은 H의 순생성률보다 높다.