• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.5-7
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• 2014

A skeletal mechanism of coal combustion was derived from a detailed coal combustion kinetic mechanism through an importance analysis of chemical pathways. The reduction process consists of roughly two parts. The first process is performed based on a connectivity analysis between species. In this process, DRGEPSA is chosen for reduction process. Strongly connected species and related reactions from the important species set as start species by the operator are sorted into the reduced mechanism. About 70% of species and reactions can be removed with a limited accuracy loss. Subsequently the second reduction process, CSP, is performed. This method focuses on an importance of each reaction and can reduce a volume of mechanism appropriately. Through these analyses, a skeletal mechanism is generated that is including 65 species and 150 reactions. The generated skeletal mechanism is verified through a comparison with the detailed mechanism in the homogeneous reactor model of CHEMKIN-PRO under wide range of conditions. The generated mechanism can give an advantage in the analysis of coal combustion characteristics in detail in large scale simulations such as LES and DNS.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1341-1346
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• 2004

Detailed flame structures of the opposed flames formed for different oxidant compositions are studied numerically. The detailed chemical reactions are modeled by using the CHEMKIN code. Only the $CO_{2}$ and $H_{2}O$ are assumed to participate by absorbing the radiative energy while all other gases are assumed to be transparent. The discrete ordinates method and a narrow band based WSGGM with a gray gas regrouping technique are applied for modeling the radiative transfer through non-homogeneous and non-isothermal combustion gas mixtures generated by the opposed flow flames. The results show that the different radiation model can cause different results for flame structures and the WSGGM with gray gas regrouping is successful in modeling the opposed flames with non-gray gas mixture. The results also show that a reasonable information on the flame structure can be obtained from the modeling by considering different chemical compositions of the oxidant.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.46-52
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• 2009

In this study the predictions of NOx in methane-air lean premixed combustion in PSR were carried out with GRI 3.0 methane-air combustion mechanism and Zeldovich, nitrous oxide, prompt, and NNH NO formation mechanism by using CHEMKIN code. The results are compared to the JSR experimental data of Rutar for the validation of the model. This study concerns about the importance of the chemical pathways. The chemical pathway most likely to form the NO in methane-air lean-premixed combustion was investigated. The results obtained with the 4 different NO mechanisms for residence time(0.5-1.6ms) and pressure(3, 4.7, 6.5 atm) are compared and discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.248-254
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• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, a pressure rise rate is a major limitation for high load range and power reduction. Recently, we were able to reduce the pressure rise rate using thermal stratification. Nevertheless, this was insufficient to produce high power. In this study, the reduction of the pressure rise rate using thermal stratification was confirmed and the HCCI engine power was increased using the boost pressure. The rate and engine power were produced by CHEMKIN and modified SENKIN. As a result of increasing the boost pressure, a higher IMEP was attained while the pressure rise rate increased only slightly in the HCCI with thermal stratification.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.10-16
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• 2005

Detailed flame structures of the counterflow flames of $CH_4/Air$ formed with $CO_2$ and $H_2O$ addition are studied numerically. The detailed chemical reactions are modeled by using the OPPDIF and CHEMKIN-II code. Only the $CO_2$ and $H_2O$ are assumed to participate in radiative heat transfer while all other gases are assumed to be transparent. The discrete ordinates method(DOM) and the narrow band based WSGGM with a gray gas regrouping technique(WSGGM-RG) are applied for modeling the radiative transfer through non-homogeneous and non-isothermal combustion gas mixtures generated by the counter flow flames. The results compared with the SNB model show that the WSGGM-RG is successful in modeling the counterflow flames with non-gray gas mixture. The numerical results show that the addition of $CO_2$ and $H_2O$ to the oxidant nozzle lowers the peak temperature and the NO concentration in flame.

• Journal of the Korean Society of Combustion
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• v.18 no.4
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• pp.12-20
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• 2013

The ignition delay time is an important factor to understand the combustion characteristics of internal combustion engine. In this study, ignition delay times of cool and thermal flame were observed separately in homogeneous charge compression ignition(HCCI) engine. This study presents numerical investigation of ignition delay time of n-heptane and alcohol(ethanol and n-butanol) binary fuel. The $O_2$ concentration in the mixture was set 9-10% to simulate high exhaust gas recirculation(EGR) rate condition. The numerical study on the ignition delay time was performed using CHEMKIN codes with various blending ratios and EGR rates. The results revealed that the ignition delay time increased with increasing the alcohol fraction in the mixture due to a decrease of oxidation of n-heptane at the low temperature. From the numerical analysis, ethanol needed more radical and higher temperature than n-butanol for oxidation. In addition, thermal ignition delay time is sharply increasing with decreasing $O_2$ fraction, but cool flame ignition delay time changes negligibly for both binary fuels. Also, in high temperature regime, the ignition delay time showed similar tendency with both blends regardless of blending ratio and EGR rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.32-39
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• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, HCCI's operating range is limited by an excessive rate of pressure rise during combustion and the resulting engine knock in high-load. The purpose of this study was to gain a understanding of the effect of only initial temperature and thermal stratification for reducing the pressure-rise rate in HCCI combustion. And we confirmed characteristics of combustion, knocking and emissions. The engine was fueled with Di-Methyl Ether. The computations were conducted using both a single-zone model and a multi-zone model by CHEMKIN and modified SENKIN.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.19-25
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• 2010

The purpose of this study is to gain a better understanding of the effects of fuel stratification on reducing the pressure-rise rate at high load in HCCI combustion. It was found that fuel stratification offers good potential to achieve a staged combustion event and reduced pressure-rise rates. The engine is fueled with Di-Methyl Ether (DME) which has unique 2-stage heat release. Numerical analysis is conducted with single and multi-zones model and detailed chemical reaction scheme is done by chemkin and senkin. Calculation result shows that proper fuel stratification prolongs combustion duration and reduce pressure rise rate. Besides IMEP, combustion efficiency and indicated thermal efficiency keep constant. However, too wide fuel stratification increases pressure rise rate and CO and NOx emissions in exhaust gas.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.117-128
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• 1999

The removal of nitrogen oxides(NOx) from $N_{2}/O_{2}$ gas using a pulsed corona discharge was investigated as a function of the reduced electric field(E/N) and the energy density(J/L). A kinetic model was developed to characterize the chemical reactions taking place in a pulsed corona discharge reactor. The model calculates the fractional concentrations of radical species at each pulse-on period and utilizes the radicals to remove NOx for the subsequent pulse-off period. Electron collision reaction data are calculated using ELENDIF program to solve Boltzmann equation for electron energy distribution function, and the subsequent chemical reactions are calculated using CHEMKIN-II program to solve stiff ODE(ordinary differential equation) problems for species concentrations. The corona discharge energy per pulse and the time-space averaged E/N were obtained by fitting the model to experimental data. The model calculation shows good agreement with the experimental data, and predicts the formation of other species such as $NO_{2}$, $O_{3}$ and $N_{2}O$.

• 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.