• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.132-137
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• 2005

The burning characteristics of interacting spherical droplet in a turbulent flow are numerically investigated. The transient combustion of 3-dimensionally arranged droplets, both the fixed streamwise droplet distances of 3 radii and 10 radii and different turbulence intensities, is studied. The results obtained from the present numerical analysis show that droplet vaporization rate for heptane droplet is insensitive to turbulence intensity, and that the transient flame configuration and retardation of droplet surface temperature augmentation with streamwise droplet spacing substantially influence vaporization process of interacting droplets. Single flame mode in which individual flames are merged into single flame, with decreasing streamwise droplet spacing, becomes faster. Therefore, vaporization rate of the second droplet with decreasing streamwise droplet spacing decreases remarkably with flame movement.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.168-175
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• 2007

Ash melting chamber is one of the key facility of the pyrolysis-melting incineration system, and it should be designed and operated very carefully for avoiding solidification of slag. In this study, an example of numerical and experimental scale-up process of the melting chamber, in which high speed air is injected to the molten slag and generates bubbles, which enhances agitation of the slag and char combustion, is presented. Cold flow test, combustion and melting test in a lab-scale (30 kg/hr) chamber and a pilot scale (200 kg/hr) chamber. Minimum energy for maintaining molten slag is derived, and it was found that the molten slag can be maintained efficiently by concentrating heat into the bubbling slag.

• Journal of ILASS-Korea
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• v.5 no.4
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• pp.66-71
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• 2000

The present study is mainly motivated to investigate the vaporization, auto-ignition and combustion processes in the high-pressure engine conditions. The high-pressure vaporization model is developed to realistically simulate the spray dynamics and vaporization characteristics in high-pressure and high-temperature environment. The interaction between chemistry and turbulence is treated by employing the Representative Interactive Flamelet (RIF) Model. The detailed chemistry of 114 elementary steps and 44 chemical species is adopted for the n-heptane/air reaction. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the multiple RIFs are introduced. Numerical results indicate that the RIF approach together with the high-pressure vaporization model successfully predicts the ignition delay time and location as well as the essential features of a spray ignition and combustion processes.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1437-1442
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• 1994

Self propagating synthesis and thermal explosion of combustion reactions were applied to Al/K2Cr2O7/Al2O3 system as the first stage for a production of magnesia-chromium refractory. Several factors related to products made by two combustion reactions were considered and properties of products were characterised. Two processes were required to preheat upto at least 80$0^{\circ}C$ for the thermal explosion and the self propagating synthesis. These processes were so violent and explosive that alumina as diluent was added to the system in order to absorb the reaction heat and reduce the reaction rate. The products consisted of crystal phases of KAl5O8, Cr2O3, Al2O3, K2CrO4, and K2Al2O4.3H2O. The amount of KAl5O8 and K2Al2O4.3H2O crystal phases of products were decreased with further addition of alumina.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.3
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• pp.302-310
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• 1997

In this paper, we find a method to improve ignitability using methanol which is prospective as an alternative fuel. The constant volume combuster is divided into main chamber and sub-cham¬ber. These two chambers are linked by an adapter which is shaped like a cup. We also compare CDI to HIS that is revised in our laboratory for making a scrutiny into the effects of ignition char¬acteristics. Besides, we analyze a flame propagation process in the main and sub-chamber through taking pictures 10, 000 frames per second by high speed camera at the state being fabricated quartz glass aside main and sub-chamber.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1989-1998
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• 1995

Characteristics of the flame propagation for normal and abnormal combustion in hydrogen premixture in a cylindrical constant-volume combustion chamber are studied numerically. A detailed hydrogen oxidation kinetic mechanism, mixture transport properties and a model describing spark ignition process are used. The calculated pressure-time history of the stable deflagration wave propagation agrees well with the experiment. The ignition of the premixture in the unburned gas, initiated by the hot spot, causes a transition from deflagration to detonation under some initial temperature and pressure. Under the initial conditions with high temperature and pressure, excessive ignition energy initiates a strong blast wave and a detonation wave that follows. The chemical reaction in the detonation wave is much more vigorous than that in the deflagration wave and the peak pressure in the detonation wave is much higher than the equilibrium value.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.765-769
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• 2001

The refuse-derived fuel(RDF) is manufactured using waste plastics-based materials and its physical and chemical properties are analyzed. The manufacturing process consists of hand picking, primary magnetic separation, crushing, secondary magnetic separation, feeding and extrusion. The RDF products have a higher calorie content of over 6, 000 ㎉/kg and high stability because the waste plastics and paper are mainly selected. The combustion flue gas of RDF products is satisfied with the emission criteria of incinerator. The heavy metal concentration of combustion byproduct from the RDF boiler is also satisfied with the criteria and appears to be lower concentration than that of a common municipal waste incinerator.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.547-550
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• 2008

A solid rocket motor has quite complex physical condition such exothermal chemical reaction in subsonic area and supersonic ex pansion in a converging-diverging nozzle. To introduce a simulation tool for compressible flow in supersonic range as well as incompressible chemical reaction zone in a whole rocket nozzle is a essential demand. Since the flow vary subsonic to super sonic, the convergence in computation becomes very low and unstable in a whole domain of rocket motor. This paper reports the 2-D Axisymmetric and simple 3-D solid propellant combustion and flow of gases in rocket motor by using a precondi tioning, shear stress turbulence modeling, AUSM(p). To simulate the simplified combustion process, Double base solid propellant is used to calculate reaction of solid propellant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.1041-1047
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• 2001

In this paper, reduction characteristics of the ac flashover voltage in the horizontal air gap of sphere-sphere/needle-needle electrode system were investigated when the combustion flame was present near the high-voltage electrodes. The voltage and current waveforms were measured, when the flashover is occurred, in order to examine the flashover polarity by flame. The reduction characteristics of ac flashover voltage were discussed with the thermal ionization process, the relative air density and the deflection phenomena in the shape of flames that changed by the corona wind and coulomb\`s force. As the results of an experimental investigation, It was found that the reduction of flashover voltages in sphere-sphere system, in comparison with the no-flame case, are 79.9 [%] for k=0, 82.9 [%] for k=0.5, 87.5 [%] for k=1.0, 85.0 [%] for h=0 [cm], 40.8 [%] for h=5 [cm] and 28.2 [%] for h=9 [cm] when ac voltage is applied.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.157-163
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• 2002

Using the CFD method, we investigated the combustion characteristics of grate-rotary kiln incinerator through the residence time, path line of flow and distributions of temperature and CO mass fraction according to the shape of mixing chamber and the existence and nonexistence of baffle at the exit of bypass duct. The results show that the now mixing and residence time could be variable according to the shape of mixing chamber and baffle, and we could know the temperature in the mixing chamber could increase too high if the combustion process on the grate retarded.