• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1789-1798
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• 1994

This paper aimed for numerical simulation of complicated gas turbine combustor with swirler. For the convenience of numerical analysis, fuel nozzle and air linear hole areas of secondary and dilution zone, which are issued to jet stream, were simplified to equivalent areas of annular type. In other to solve these problems, imaginary source terms which are corresponded to supplied fuel amount were added to those of governing equation. Chemical equilibrium model of infinite reaction rate and $k-{\epsilon}-g$ model with the consideration of density fluctuation were applied. As the result, swirl intensity contributed to mixing of supplied fuel and air, and to speed up the flame velocity than no swirl condition. Temperature profiles were higher than experimental results at the upstream and lower at the downstream, but total energy balance was accomplished. As these properties showed the similar trend qualitatively, simplified simulation method was worth to apply to complicated combustor for predicting combustion characteristics.

• Journal of Mechanical Science and Technology
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• v.16 no.1
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• pp.116-124
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• 2002

In order to investigate the soot formation and oxidation processes, we employed the two variable approach and its source terms representing soot nucleation, coagulation, surface growth and oxidation. For the simulation of the taxi-symmetric turbulent reacting flows, the pressure-velocity coupling is handled by the pressure based finite volume method. We also employed laminar flamelet model to calculate the thermo-chemical properties and the proper soot source terms from the information of detailed chemical kinetic model. The numerical and physical models used in this study successfully predict the essential features of the combustion processes and soot formation characteristics in the reacting flow field.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.7
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• pp.841-848
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• 1997

Combustion of gaseous fuel combustor in a high temperature vitiated air stream was studied with computer simulation. It is for application to afterburner of gas turbine engine which the exact mechanism is not yet clarified. As the jet velocity from fuel nozzle is very high and the geometry of combustor is three dimensional complex structure, many time and money are required to have good results. To consider this demerit, it is simplified to 2-dimensional and modified with the nozzle hole area to same area of annual status. As the thickness of annual is too thin, it is to divide with the many grids for reasonable results. Accordingly, new method which injected fuel mass, momentum and energy are added to source terms of each governing conservation equation as a source terms is introduced like as two phase analysis. Reaction rate is determined by taking into account the Arrhenius reaction based on a single step reaction mechanism. It is focused to temperature and product concentration distribution at each equivalence ratio of inlet hot product.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.231-238
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• 1998

Cr3C2 -dispersed TiC composites were prepared via HPCS(high pressure-self combustion sintering) pro-cess using mixtures of Ti, Cr and a carbon source for the purpose of increasing the facture toughness and sinterability of TiC. In this study the microstructure and properties of the composites were investigated in terms of relation to the carbon source the particle size of Ti and the amount of Cr. It was found that car-bon black was the most effective carbon source among the various carbon sources tested and the reaction was more effective as the particle size of Ti decreased. Among the sintered composites of Ti-C-Cr system the one with 30wt% Cr showed the best physical properties with 0.5% in apparent porosity 98.8% in re-lative density 18.2 GPa in hardness and 4.46 MPa.m1/2 in fracture toughness. In addition it was observed that the lattice constant of TiC decreased gradually with increasing the amount of Cr.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.527-534
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• 2012

Thermal batteries are primary batteries that use molten salts as an electrolyte and employ an internal pyrotechnic source to heat the battery stack to operating temperatures, typically between 450 and $550^{\circ}C$. The unit cell of thermal batteries consists of an anode, an electrolyte, a cathode, a heat pellet and a current collector. The heat source for such batteries is typically heat pellets based on $Fe/KClO_4$. The elevated temperature by combustion of heat pellet is supposed to cause a flatness non-uniformity, buckling, with a lateral extension diameter of current collector. This paper mainly focused on the combustion and buckling model of current collector to simulate the effect of heat source. Mechanical stresses in the current collector caused by thermal stress is a critical design consideration of thermal batteries because the internal short circuit could be occurred.

• Journal of the Korean Society of Combustion
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• v.10 no.4
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• pp.24-32
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• 2005

Various types of plasma source applied in $CH_4$ decomposition process are compared. DBD by pulse and AC power, spark by pulse and AC power, rotating arc and hollow cathode plasma are chosen to be compared. The results show that $CH_4$ conversion per given unit power is relatively high in hollow cathode plasma and rotating arc that induces rather high temperature condition and that is why both thermal dehydration and plasma induced decomposition contribute for the overall process. In case of DBD wherein high temperature electron and low temperature gas molecule coexist, the process shows low conversion rate, for in rather low temperature condition the contribution of thermal dehydration is lowered. Selectivity of $C_2H_6$ and $C_2H_2$ is shown to be a good parameter of the relative contribution of plasma chemistry in the overall process. From the results we concluded that required condition of plasma source for a cost effective and high yield $CH_4$ decomposition is to have characteristics of both thermal plasma and non thermal plasma in which temperature is high above a certain threshold state for thermal dehydration and electron induced collision is maximized in the same breath.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.96-101
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• 2005

Cogeneration is an energy conversion process, where electricity and useful heat are produced simultaneously in one process. Also, carbon dioxide emissions can be reduced as well. The cogeneration process may be based on the use of steam, gas turbines or combustion engines. However, there have been few models with an output of less than 100 kilowatt. In the present study, a spark ignited gas engine with generation output of 10 kilowatts was developed for micro cogeneration package. The gas engine shows 29.2$\%$ of thermal efficiency under Stoichiometric combustion and 33.6$\%$ of thermal efficiency under lean combustion. NOx emission shows less than 10ppm at 13$\%$ oxygen under stoichiometric combustion and about 100ppm at 13$\%$ oxygen under lean combustion.

• Clean Technology
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• v.12 no.2
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• pp.78-86
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• 2006

Computational analyses are conducted on the combustion characteristics of the coal- and the biomass-derived synthetic gases with low-Btu heating value in gas engine. Using thermochemical analyses on the synthetic gases, combustion pressure, temperature, exhaust gas composition, NO emission and engine power are predicted and the predicted results are compared with small-scale pilot engine test results. In order to investigate the unsteady combustion phenomena in gas engine combustion chamber, CFD analyses are carried out on the coal and the biomass synthetic gases and their computed results are compared to provide the guidelines for the design modification and the tuning of the gas engine burning the synthetic gases as alternative fuels.

• Journal of ILASS-Korea
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• v.1 no.2
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• pp.24-32
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• 1996

Most of the research of small engines to date focused on developing spark ignition engines occupied much parts. Recently the number of a small direct injection diesel engine applied in small cars has been increased and considered as a next generation power source for passenger cars because of its high efficiency. Therefore the combustion chamber becomes smaller and the fuel injection pressure goes higher, which makes fuel sprays impinged easily on the combustion chamber walls. When strong swirls are not induced, the fuel may not mix with air because of fuel deposition on the wall. As a positive way, the combustion chamber systems which is using spray wall impaction has been introduced and assessed by an experimental or a simulate manner. In these systems the raised lands are positioned in tile chamber for spray impaction in order to break up the fuel drops into much smaller and direct them into desirable direction. This study addresses to the effects of rho position and size of the raised land or glow plug to help the chamber design using spray wall impaction. The characteristics of the spray impinged on various lands are investigated and compared with each other. Then the chamber shapes are discussed with the characteristics and their proper position and size is proposed in any chamber volume.

• Journal of the Korean Society of Combustion
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• v.12 no.4
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• pp.8-13
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• 2007

Plasma assisted combustion is an old subject for the combustion society, but recently, the subject is refocused partly because techniques for non-thermal plasmas are progressed significantly, and partly because there are lots of applications which need to be overcome by a new reaction technology. In the present study, we have developed plasma assisted burner (plasma burner), which can be used as a heating source in a diesel particulate filter system. The burner can burn 20-60 cc/min of diesel fuel with 50 lpm of fresh air in an exhaust pipe of 2.0 liter diesel engine. Using 20 cc/min of diesel fuel, an exhaust temperature for 2.0 liter diesel engine can be raised up to around $600^{\circ}C$ for a wide range of engine speed (idle-3,000 rpm). The characteristics of the plasma burner are reported, and the possible operating mechanism of it will be discussed based on the effects of an electric field and a plasma on flames.