• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.166-173
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• 2007

A numerical study was conducted to have the effect of $CO_2$ addition to fuel on the chemical reaction mechanism with the change of the initial concentration of $CO_2$ and the axial velocity gradient. From this study, it was found that there were two serious effects of $CO_2$ addition on a non-premixed flame ; a diluent effect by the reactive species reduction and chemical effect of the breakdown of $CO_2$ by the third-body collision and thermal dissociation. Especially, the chemical effect was serious at the lower velocity gradient of the axial flow. It was certain that the mole fraction profile of $CO_2$ was deflected and CO was increased with the initial concentration of $CO_2$. It was also ascertained that the breakdown of $CO_2$ would cause the increasing of CO mole fraction at the reaction region. It was also found that the addition of $CO_2$ did not alter the basic skeleton of $H_2-O_2$ reaction mechanism, but contributed to the formation and destruction of hydrocarbon products such as HCO. The conversion of CO was also suppressed and $CO_2$ played a role of a dilution in the reaction zone at the higher axial velocity gradient.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.1
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• pp.47-58
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• 2014

The characteristics of flame shape, laminar burning velocity, emissions and heat flux of stagnation point in premixed impinging jet flame of syngas fuel with 10% hydrogen content were experimentally investigated. Also, the adiabatic temperature and burning velocity are calculated by Chemkin package with USC-II mechanism. The equivalence ratios(0.8~5.0) and dimensionless separation distance(2.0~5.0) with fixed Reynolds number(1800) are main parameters in this work. Different flame shapes and colors were observed for different impingement conditions. The experimental results of burning velocity by flame surface area have a consistent with previous works and numerical simulation of this work. The inner flame length could be predicted with the ratio of mixture velocity and burning velocity from a simple formulation by the laminar burning velocity definition. It has been observed that the heat fluxes at stagnation point are directly affected by the flame shape including the separation distance. The emission results in impinging flame of syngas fuel show that the characteristics of $NO_x$ emission traced well with adiabatic temperature trend and CO emission due to fuel rich condition increased continuously with respect to the equivalence ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.51-59
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• 2005

Co-flow laminar diffusion flames' temperature has been studied experimentally for ethylene$(C_2H_4)$ using a co-flow burner in order to investigate the characteristics of diffusion flame's temperature distribution. The temperature distributions in the flame were measured by rapid insertion of a R-type thermocouple. The measurement area was divided into three zones. 1st area was expect to created PAH zone, Il nd area was expect to form soot zone, which is known to generate most soot volume fraction, and III rd area was expect to from soot oxidization zone. Also The temperature along the flame y-axis as a fuel quantity was measured. As a results, we have measured temperature neglecting the effect of soot particles attached to the thermocouple junction, which is close to the nozzle and upstream zone has a unstable flow in co-flow diffusion flame and acquires that the flame y-axis temperature has a uniform temperature in the generated soot volume fraction zone(II nd).

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.819-827
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• 1987

The purpose of the present investigation is to examine the effect of water addition on combustion efficieny. In this research, fuel and additive water are injected into a burner in the form of vapors through separate needle valves, the flame temperature and concentrations of soot, CO and unburned hydrocarbons were measured in a premixed flame. The results are obtained to be: In the fuel lean region, the reduction rate of CO, soot and HC by water injection increases slightly, but there is no change in the combustion efficiency. On the other hand, in the fuel rich region, the reduction rate of CO, Soot and HC by water injection increases more than that of the fuel lean region. Accordingly, combustion efficiency increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.51-58
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• 2002

The RPV(Reaction Progress Variable) combustion model has been applied to numerically investigate the effects of Damkohler number on the superequilibrium concentration and flame structure in the nonpremixed turbulent flames. Computations are performed for the two turbulent jet flames of CO/H$_2$/N$_2$(40/30/30 volume percent) having the same jet Reynolds number of 16,700 but different nozzle diameters(4.58mm and 7.72mm). The detailed discussions have been made for the interaction between fluid dynamics and chemistry in the flame field.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.1-8
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• 2007

The purpose of this study is to conduct a survey of the flame stability range and the emission characteristics for the optimum design of turbulent premixed flat burner. For that, the flame stability range was selected by the direct photography of the flame. And the mean temperature and CO, HC, $CO_{2}\;and\;O_{2}$ concentration distributions by changing the excess air ratio were measured. As results of this study, the flame stability range turned out to be getting narrower as fuel flow was increased. The blue flame mode was more excellent than any other flame modes in the emission characteristics by excess air ratio change. And the emission characteristics by fuel flow change were best at fuel flow 1l/min. Also, we found combustion noise during experiment of flame stability range. It had nothing do with excess air ratio range.

• Fire Science and Engineering
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• v.28 no.3
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• pp.34-42
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• 2014

The concentrations of inert gases ($N_2$, Ar, $CO_2$ and He) required to induce the flame instabilities such as swing, rotation, lifted and blow-out were measured in a cup burner nonpremixed flames for $CH_4$ and $C_3H_8$ fuels. Quantitative differences in the extinguishing concentration with fire suppression criteria (i.e. blow-out or onset of flame instability) were also examined. It was found that the difference in extinguishing concentration was increased with the appearance of lifted flame and the low extinguishing performance of inert gaseous. The maximum difference in extinguishing concentration with the suppression criteria was approximately 35% at the highest fuel velocity condition (1.3 cm/s) for the $C_3H_8$-air nonpremixed flame. It can be also expected that the extinguishing concentration by the criteria based on the onset of flame instability will provide the useful information from the viewpoint of the accurate and economical design concentration.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1616-1624
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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.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.215-218
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• 2012

In this study, syngas laminar burning velocities with various hydrogen contents were studied using both experimental measurements and kinetic simulations. The laminar burning velocities were measured by the angle method of Bunsen flame configuration and the numerical calculations including burning velocities were made using CHEMKIN Package with USC-Mech II. A large range of syngas mixture compositions such as 10:90%, 25:75%, 50:50%, 75:25% and equivalence ratio from lean condition of 0.5 to rich condition of 5.0 have been conducted. The experimental results of burning velocity were in good agreement with previous other research data and numerical simulation. Also, it was shown that the experimental measurements of laminar burning velocity linearly increased with the increasing of $H_2$ content although the flame speed of hydrogen is faster about ten times than carbon monoxide. This phenomenon is attributed to the rapid production of the hydrogen related radicals such as H and OH at the early stage of combustion, which is confirmed the linear increasing of radical concentrations on kinetic simulation.