• Title/Summary/Keyword: EINO

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The Influence of a Vortex on a Freely Propagating Laminar Methane-Air Flame

  • Lee, Ki-Yong
    • Journal of Mechanical Science and Technology
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    • v.18 no.5
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    • pp.857-864
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    • 2004
  • The change in the NO emission indices (EINO) in a two-dimensional plane has been investigated, which is due to the interaction between a vortex and methane-air flames established at different equivalence ratios, by solving the field equation. After solving the field equation, the spatial distribution of G-values is obtained. The NO emission index is calculated after applying the appropriate relation between the G-values and the NO production rate or the mass fraction of methane obtained from the library of freely propagating flames created from detailed simulations. When a vortex exists in a reacting flow field, in general EINO slightly increases, whereas ElNO is lowered in the vicinity of the vortex regardless of flow direction. A change in vortex size has negligible impact on EINO$\_$T/ but increasing the vortex strength slightly increases EINO$\_$T/ in the domain of this study.

Computational Study of the MILD Combustion and Pollutant Emission Characteristics in Jet Flow Field (제트 유동장에서의 마일드 연소 및 오염물질 배출특성에 관한 전산해석 연구)

  • Kim, Yu Jeong;Song, Keum Mi;Oh, Chang Bo
    • Journal of the Korean Society of Combustion
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    • v.17 no.4
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    • pp.60-65
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    • 2012
  • The MILD combustion and pollutant emission characteristics were investigated computationally. The temperature of supplying air-stream and mixing rate (${\Omega}$) of exhaust gas in the air-stream were adjusted to investigate the effects of those parameters on the MILD combustion in jet flow field. The emission indices for NO (EINO) and CO (EICO) were introduced to quantify the amount of those species emitted from the combustion. The high-temperature region disappeared gradually as the mixing rate increased for fixed air-stream temperature. The EINO increased as the air-stream temperature became higher for fixed mixing rate, and the EINO decreased dramatically with increasing the mixing rate for each air-stream temperature condition. The EICO also decreased with increasing the mixing rate and it was nearly independent of air-stream temperature except for near ${\Omega}$ = 0.7. It was found that the CO supplied in the air-stream can be destroyed in the MILD combustion over the certain mixing rate.

The Study of Effects of Additives on the NOx Formation in $H_{2}/O_{2}/N_{2}$ Premixed Flames with Oxygen Enrichments (산소부화된 $H_{2}/O_{2}/N_{2}$ 예혼합 화염에서 첨가제가 NOx 생성에 미치는 영향 연구)

  • Lee, Ki-Yong;Kwon, Young-Suk
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.241-246
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    • 2003
  • Numerical simulations are performed at atmospheric pressure in order to understand the effect of additives on flame speed and the NOx formation in freely propagating $H_{2}/O_{2}/N_{2}$ flames with oxygen enrichments. A chemical kinetic mechanism is developed, which involves 26 gas-phase species and 99 reactions. Under several equivalence ratios and oxygen enrichments, flame speeds are calculated and compared with those obtained from the experiments, the results of which is in good agreement. As hydrogen chloride as additive is added into $H_{2}/O_{2}/N_{2}$ flames with low oxygen enrichments, its chemical effect causes the decrease of flame speed, radical concentration, and the NO production rate. It is found that the chemical effect of additive has much more influence on the reduction of EINO than its physical effect. However, in flames with very high flame temperature the physical effect rather than the chemical effect becomes more important on the reduction of EINO.

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Simulation Analysis of MILD Combustion and NOx Formation for Methane-Hydrogen Mixture Using 0D Model (0D 모델을 활용한 메탄-수소 혼소에 따른 MILD 연소 및 NOx 배출 특성 해석 연구)

  • AN, SOJEONG;PARK, JINJE;BAE, YOUN-SANG;LEE, YOUNGJAE
    • Journal of Hydrogen and New Energy
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    • v.33 no.4
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    • pp.400-412
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    • 2022
  • Hydrogen with high chemical reactivity and combustion efficiency, is expected to reduce greenhouse gas and CO emission. However, there is a problem of increase in NOx emission due to hydrogen combustion. MILD combustion technology has been proposed to resolve NOx emission. In this study, the characteristics of MILD combustion and NOx formation by flue gas recirculation (KV) in CH4-H2 mixture were analyzed and predicted using 0D premixed combustion model. The ignition delay time became shorter as the hydrogen co-firing rate increased, and longer as the recirculation rate increased. For NOx emission, EINO decreased as the KV increased, but EINO increased as the hydrogen co- firing rate increased. In particular, EINO was predicted to increase significiently above 80% hydrogen. Through the pathway analysis of NO formation, it was found that the influence of N2O intermediate route and NNH route was enhanced for hydrogen co-firing.

The Effect of HCl on the NOx Reduction in $H_2/HCl/Air$ Premixed Flame ($H_2/HCl/Air$ 예혼합 화염에서 NOx 저감을 위한 HCl의 효과)

  • Lee, Ki-Yong;Kwon, Young-Suk;Sin, Sung-Su
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.2180-2185
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    • 2003
  • Numerical simulations of freely propagating flames burning $H_2/HCl/Air$ mixtures are performed at atmospheric pressure in order to understand the effect of HCl on the NOx reduction. A chemical kinetic mechanism is developed, which involves 26 gas-phase species and 99 reactions. Under several equivalence ratios the flame speeds are calculated and compared with those obtained from the experiments, the results of which is in good agreement. As HCl is added into $H_2/Air$ flame as additive, its chemical effect causes the reduction of radicals (H, OH, and O), and then the decrease of the net rate of NO production. It is found that the chemical effect of additive has much more influence on the reduction of EINO than its physical effect.

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The Function of Halogen Additive in $CH_4/O_2/N_2$ Flames ($CH_4/O_2/N_2$ 화염에서 할로겐 첨가제의 역할)

  • Lee, Ki-Yong;Shin, Sung-Su
    • 한국연소학회:학술대회논문집
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    • 2003.12a
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    • pp.209-214
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    • 2003
  • Numerical simulations are performed at atmospheric pressure in order to understand the effect of additives on flame speed, flame temperature, the radical concentration, the NOx formation in freely propagating $CH_4/O_2/N_2$ flames. The additives used are carbon dioxide and hydrogen chloride which have a combination of physical and chemical behavior on hydrocarbon flame. In the flame established with the same mole of methane and additive, $CO_2$ addition significantly contributes toward the reduction of flame speed and flame temperature by the physical effect, whereas addition of HCl mainly does by the chemical effect. The impact of HCl addition on the decrease of the radical concentration is about 1.6-1.8 times as large as $CO_2$ addition. Hydrogen chloride addition is higher on the reduction of EINO than $CO_2$ addition because of the chemical effect of HCl.

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Numerical Study on Flame Structure and NO Formation Characteristics in Oxidizer-Controlled Diffusion Flames (산화제 제어 확산화염의 화염구조 및 NO 생성 특성에 관한 수치해석적 연구)

  • Lee, Chang-Eon;Han, Ji-Ung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.5
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    • pp.742-749
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    • 2002
  • Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen -enhanced(CH$_4$/O$_2$-$N_2$) and oxygen-enhanced-EGR(CH$_4$/O$_2$-$CO_2$) counter diffusion flame with various strain rates. A small amount of $N_2$is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$contamination by $O_2$production process or air infiltration. The results are as follows : In CH$_4$/O$_2$-$CO_2$flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In CH$_4$/O$_2$-$N_2$flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case CH$_4$/O$_2$-$CO_2$flame contains more than 40% $CO_2$it is possible to maintain the same EINO as that of CH$_4$/Air flame with accomplishing higher temperature than that of CH$_4$/Air flame. EINO decreases with increasing strain rate, and those effects are augmented in CH$_4$/O$_2$flame.

Structure and NO formation characteristics of oxidizer-controlled diffusion flames (산화제 제어 화염의 구조 및 NO 생성 특성)

  • Han, Ji-Woong;Lee, Chang-Eon
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.185-190
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    • 2001
  • Numerical Study with detailed chemistry has been conducted to investigate the flame structure and NOx formation characteristics in oxygen-enhanced$(CH_4/O_2-N_2)$ and oxygen-enhanced-EGR$(CH_4/O_2-CO_2)$ counter diffusion flame with various strain rates. A small amount of $N_2$ is included in oxygen-enhanced-EGR combustion, in order to consider the inevitable $N_2$ contamination by $O_2$ production process or air infiltration. The results are as follows : In $CH_4/O_2-CO_2$ flame it is very important to adopt a radiation effect precisely because the effect of radiation changes flame structure significantly. In $CH_4/O_2-N_2$ flame special strategy to minimize NO emission is needed because it is very sensitive to a small amount of $N_2$. Special attention is needed on CO emission by flame quenching, because of increased CO concentration. Spatial NO production rate of oxygen-enhanced combustion is different from that of air and oxygen-enhanced-EGR combustion in that thermal mechanism plays a role of destruction as well as production. In case $CH_4/O_2-CO_2$ flame contains more than 40% $CO_2$ it is possible to maintain the same EINO as that of $CH_4/Air$ flame with accomplishing higher temperature than that of $CH_4/Air$ flame. EINO decreases with increasing strain rate, and those effects are augmented in $CH_4/O_2$ flame. Complementary study is needed with extending the range of strain rate variation.

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Effects of Flow Excitation on the Nitrogen Oxide Emission of a Non-Premixed Flame (유동장 자극이 화염의 질소산화물 배출에 미치는 영향)

  • 이기만
    • Fire Science and Engineering
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    • v.18 no.2
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    • pp.34-40
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    • 2004
  • The effects of external flow excitation with various frequencies and amplitudes on the flame behavior and pollution emission characteristics from a laminar jet flame are experimentally investigated. Measurements of $NO_x$ emission indices ($EINO_x$), performed in vertical lifted flame like turbulent with various exciting amplitude at a constant resonance frequency, have been conducted. It was also conducted to investigate the effects of excited frequency at a constant exciting amplitude on $NO_x$ emissions with a various frequency ranged 0 Hz to 2 KHz. From the vertical lifted turbulent flame of the excited jet with resonance frequency by strong excitation was shown that the dependence of $NO_x$ emission could be categorized into three groups Group I of long flame length with high disturbances yielding high $NO_x$ emission, Group II of intermediate flame length and relative narrow flame volume with low disturbance yielding low $NO_x$ emission and Group III of long flame length and large flame volume with high time & space disturbances behaviour yielding high $NO_x$ emission.

A Numerical Analysis of the NO Emission Characteristics in $CH_4/Air$ Counterflow Premix Flame (메탄/공기 대향류 예혼합화염의 NO 발생특성에 관한 수치해석)

  • Cho, Eun-Seong;Chung, Suk-Ho
    • Journal of the Korean Society of Combustion
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    • v.9 no.4
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    • pp.22-27
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    • 2004
  • Lean premix combustion is a best method in low $NO_x$ gas turbine combustor and we must know the characteristics of NO emission in high temperature and pressure condition in premix flame. Numerical analysis was performed to investigate the NO emission characteristics by adopting a counterflow as a model problem using detailed chemical kinetics. Methane $(CH_4)$ was used as a test fuel which is the main fuel of natural gas. The tested parameters were stretch rate, equivalence ratio, initial temperature, and pressure in premix flame. Results showed that NO emission was high in low stretch rate, near stoichiometric equivalence ratio, high initial temperature, and high pressure. Also, the pressure effect was sensitive in high temperature condition.

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