• Bulletin of the Korean Chemical Society
• /
• v.25 no.4
• /
• pp.533-538
• /
• 2004

Canonical sampling method has been presented to generate the initial conditions for reactive flux studies of organic reactions in water. Velocity Verlet version of Nose-Hoover chain dynamics algorithm has been employed to sample the initial conditions according to canonical distribution. The unstable normal mode of a transition state has been introduced to define a dividing plane separating reactant and product regions in reaction processes. This method has been implemented and tested for the case iels-Alder reaction of methyl vinyl ketone (MVK) and cyclopentadiene (CPD) in water, providing a reliable tool for further reactive flux molecular dynamics studies in condensed media.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.228-232
• /
• 2010

In this paper, various operating parameters of stream reforming process from methane in preconverter for MCFC is studied by numerical method. Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). The hydrogen production is tested with different wall temperature, Gas Hourly Space Velocity(GHSV), and different reactor shapes.

• Advances in Energy Research
• /
• v.4 no.3
• /
• pp.213-221
• /
• 2016

The main purpose of this work is to test the validation of use of a four step reaction mechanism to simulate the laminar speed of hydrogen enriched methane flame. The laminar velocities of hydrogen-methane-air mixtures are very important in designing and predicting the progress of combustion and performance of combustion systems where hydrogen is used as fuel. In this work, laminar flame velocities of different composition of hydrogen-methane-air mixtures (from 0% to 40% hydrogen) have been calculated for variable equivalence ratios (from 0.5 to 1.5) using the flame propagation module (FSC) of the chemical kinetics software Chemkin 4.02. Our results were tested against an extended database of laminar flame speed measurements from the literature and good agreements were obtained especially for fuel lean and stoichiometric mixtures for the whole range of hydrogen blends. However, in the case of fuel rich mixtures, a slight overprediction (about 10%) is observed. Note that this overprediction decreases significantly with increasing hydrogen content. This research demonstrates that reduced chemical kinetics mechanisms can well reproduce the laminar burning velocity of methane-hydrogen-air mixtures at lean and stoichiometric mixture flame for hydrogen content in the fuel up to 40%. The use of such reduced mechanisms in complex combustion device can reduce the available computational resources and cost because the number of species is reduced.

• Journal of the Korean Society of Combustion
• /
• v.5 no.1
• /
• pp.7-18
• /
• 2000

Numerical simulations of counterflow non-premixed $CH_4/C_2HCl_3/Air$ flames added 8%(by volume) C2HCl3 on the fuel side are conducted at atmospheric pressure using a detailed chemical reaction mechanism in order to understand the effect of strain rates. A detailed sensitivity analysis is also performed in order to assess the relative influence of each reaction on the flame established at a strain rate of 200s-1. The structure of flames (i.e., temperature, velocity, and concentration of species) established at both a strain rate of 150s-1 and 300s-1 are investigated. As the strain rate increases, the "flame zone" is restricted to a narrower range and the position of maximum temperature is shifted to the fuel side. The concentrations of major species, H2O, CO, H2, HCl, Cl2, and Cl are decreased with increased strain rate. The reaction involving chlorine, CH4 + Cl $\rightarrow$ CH3 + HCl, instead of the reaction, CH4 + H $\rightarrow$ CH3 + H2 influences the consumption of methane. C2HCl3 + OH $\rightarrow$ CHCl2 + CHOCl and HCl + OH $\rightarrow$ H2O + Cl, are major reactions, through which OH radicals are consumed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.10
• /
• pp.1303-1310
• /
• 2001

In order to be applicable to the combustion modelling of stratified charged combustion like that of - lean burn and GDI engine, the correlations of laminar burring velocities fur several hydrocarbon fuels and methanol are needed over a wide range of equivalence ratio, pressure and temperature. In this study, these correlations are modeled in the 1311owing form based on the experimental and Muller\`s modeling results for several fuels, where $\alpha$, ξ, and ξ are functions of pressure and temperature, $S_{L}$ =$\alpha$ exp[-ξ($\Phi$-$\Phi$$_{m}$)$^{2}$ -exp {-ζ($\Phi$-$\Phi$$_{m}$)}-ζ($\Phi$-$\Phi$$_{m}$)]. By using the results calculated by PREMIX code with Sloane\`s detailed chemical reaction mechanism for propane, it is verified that the coefficients of the abode modeling can be determined by considering laminar burning velocity data only in a range of equivalence ratio less than $\Phi$$_{m}$. Therefore, Muller\`s modeling results can be adopted leer modeling of the pressure and temperature dependency. Compared with the results of the existing Keck'and Gulder's models, those of the present one showed the good agreement of the recent experimental data, especially in the range of lean and rich sides.s.des.s.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.704-709
• /
• 2000

Laminar burning velocities of propane- and iso-octane-air mixtures have been numerically modelled over a wide range of equivalence ratio, pressure and temperature. These correlations are applicable to the modelling of stratified charged combustion like that of lean bum and GDI engine combustion. The numerical models are based on the results calculated by PREMIX code with Sloane's detailed chemical reaction mechanism for propane and FlameMaster code with Peters' for iso-octane. Laminar burning velocity for two fuels showed a pressure and temperature dependence in the following form, in the range of $0.1{\sim}4MPa$, and $300{\sim}1000K$, respectively. $S_L={\alpha}\;{\exp}[-\xi({\phi}-{\phi}_m)^2-{\exp}\{-{\xi}({\phi}-{\phi}_m)\}-{\xi}({\phi}-{\phi}_m)]$ where ${\phi}_m=1.07$, and both of ${\alpha}$ and ${\xi}$ are functions of pressure and temperature. Compared with the results of the existing models, those of the present one showed the good agreement of the recent experiment data, especially in the range of lean and rich sides. Judging from the calculated results of the stratified charged combustion by using STAR-CD, the above modelling prove to be more suitable than the other ones.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.713-719
• /
• 2016

The NOx conversion properties of Mn-Cu-$TiO_2$ and $V_2O_5$/$TiO_2$ catalysts were studied for the selective catalytic reduction (SCR) of NOx with ammonia. The performance of the catalysts was investigated in terms of their $NOx$ conversion activity as a function of the reaction temperature and space velocity. The activity of the Mn-Cu-$TiO_2$ catalyst decreased with increasing reaction temperature and space velocity. However, the activity of the $V_2O_5$/$TiO_2$ catalyst increased with increasing reaction temperature. High activity of the Mn-Cu-$TiO_2$ catalyst was observed at temperatures below $200^{\circ}C$. H2-TPR and XPS analyses were conducted to explain these results. It was found that the activity of the Mn-Cu-$TiO_2$ catalyst was influenced by the thermal shock caused by the change of the initial reaction temperature, whereas the $V_2O_5$/$TiO_2$ catalyst was not affected by the initial reaction temperature. In the case of catalyst C, the $NO_x$ conversion efficiency decreased with increasing space velocity. The decrease in the $NO_x$ conversion efficiency with increasing space velocity was much less for catalyst D than for catalyst C.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.96.1-96.1
• /
• 2011

Solid oxide fuel cells(SOFCs) can convert the chemical energy of fuel into electricity directly. With the rising fuel prices and stricter emission requirement, SOFCs have been widely recognized as a promising technology in the near future. In this study, lean premixed flame using the orifice swirl burner was analyzed numerically and experimentally. We used the program CHEMKIN and the GRI 3.0 chemical reaction mechanism for the calculation of burning velocity and adiabatic flame temperature to investigate the effects of equivalence ratio on the adiabatic flame temperature and burning velocity respectively. Burning velocity of hydrogen was calculated by CHEMKIN simulation was 325cm/s, which was faster than that of methane having 42 cm/s at the same equivalence ratio. Also Ansys Fluent was used so as to analysis the performance with alteration of swirl structure and orifice mixer structure. This experimental study focused on stability and emission characteristics and the influence of swirl and orifice mixer in Solid Oxide Fuel Cell Systme burner. The results show that the stable blue flame with different equivalence ratio. NOx was measured below 20 ppm from equivalence ratios 0.72 to 0.84 and CO which is a very important emission index in combustor was observed below 160 ppm under the same equivalence region.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.91.1-91.1
• /
• 2010

The Reforming system is an effective method to generate hydrogen which uses for fuel cell system. The purpose of this study is to present characteristics of an autothermal reformer at various operating conditions and to investigate ideal conditions for reforming efficiency. Dominant chemical reactions are Full Combustion, Steam Reforming reaction, Water-Gas Shift reaction and Direct Steam Reforming reaction. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio, Steam to Carbon Ratio and Gas Hourly Space Velocity. Autothermal reformer is filled with catalysis of a packbed-bed type. Using numerical approach, we have investigated on various reaction conditions.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.9
• /
• pp.1369-1380
• /
• 2005

The reaction of methyl radical with iodine molecule on an attractive potential energy surface is studied by classical trajectory procedures. The reaction occurs over a wide range of impact parameters with the majority of reactive events occurring in the backward rebound region on a subpicosecond scale. A small fraction of reactive events take place in the forward hemisphere on a longer time scale. The ensemble average of reaction times is 0.36 ps. The occurrence of reactive events is strongly favored when the incident radical and the target molecule align in the neighborhood of collinear geometry. Since the rotational velocity of I2 is slow, the preferential occurrence of reactive events at the collinear configuration of $CH_3{\ldots}I{\ldots}$I leads to the reaction exhibiting an anisotropic dependence on the orientation of $I_2$. During the collision, there is a rapid flow of energy from the $H_3C{\ldots}$I interaction to the I-I bond. The $CH_3I$ translation and $H_3C$-I vibration share nearly all the energy released in the reaction, and the distribution of the vibrational energy is statistical. The reaction probability is $\cong$0.4 at the $CH_3$ and I2 temperatures maintained at 1000 K and 300 K, respectively. The probability is weakly dependent on the $CH_3\;and\;I_2$ temperatures between 300 K and 1500 K.