• Polymer(Korea)
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• v.29 no.2
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• pp.211-215
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• 2005

Stabilization process is absolutely necessary to convert the precursor fibers into chemically, physically, thermally and structurally stable carbon fibers. Especially, it is critically important for rayon fibers experiencing severe weight loss and thermal shrinkage occurring at the stabilization stage below $400^{\circ}C$. The stabilization of rayon fibers strongly depends not only on stabilization temperature but also on heating rate, chemical pre-treatment, atmosphere, and so on. In the present study, the weight loss, fiber diameter change occurred in the furnace during the stabilization process for rayon fibers produced with various heating rates and in the absence and presence of phosphorous-based flame retardants and the thermal stability of the stabilized fibers were investigated. The result indicates that the weight, diameter and thermal stability of the rayon fibers are significantly affected by the type and amount of the flame retardant used. It is also suggested that the pre-treatment of rayon fibers with a concentration lower than $3\;vol\%$ of phosphoric acid is most desirable for further carbonization process of stabilized rayon fibers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.315-318
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• 2004

The Advantages of hot machining are the reduction of cutting forces, tool wear, and the increase of material removal rates. In this study, a hot-machining characteristics of milling by CBN tip was exprimentely analyzed, and the influence of the surface temperature and the depth of cut on the tool life were investigated. The selection of a heating method for obtaining ideal temperature of metals in machining is important. Faulty heating methods could induce unwanted structural changes in the workpiece and increase the cost. This study uses gas flame heating. It is obtained that tungsten carbide-alloyed has a recrystallisation temperature range of $800-1000^{\circ}C$ which is the high heating temperature that might induce unwanted structural changes. If it is performed at temperatures higher than $800^{\circ}C$ in machining, the possibility of unwanted structural changes and the increased wear of tool can be shown. Consequently, in hot machining of tungsten carbide-alloy, this study has chosen $400^{\circ}C-600^{\circ}C$ because the heating temperature might be appropriate in view of the cost and workpiece considerations. The results of this study experimentally shows a new machining method for tungsten carbide-alloyed that decreases the wear rate of machining tools

• Journal of the Korean Society of Safety
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• v.33 no.3
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• pp.15-20
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• 2018

There have been a number of major fatal fire accidents in Korea recently. The number of fires in 2017 were 44,178, which is not only increasing number of fires but also increasing in casualties. Particularly, the fire at Jecheon Sports Center, which suffered many casualties, is expected to have a huge impact. The cause of the fire has not been determined yet, but heat waves on the ceiling have also been pointed out. As such, the copper heating waves, which are used as a preventive measure against damage of pipes due to freezing of pipes, etc., always have a fire hazard. To determine the possibility of a flame-resistant heated fire, a positive electric cable product was used to artificially ignite and analyze the results. In case of a short circuit, the external covering of the positive electric cable is damaged, but not short circuit unless the heating material surrounding the wire is damaged. Due to the characteristics of heating cable for preventing copper waves, the chances of insulation becoming more severe due to moisture and temperature changes are higher than normal wires. If the internal heating system is carbonized by insulating deterioration without damage to the outer coating, it is likely to cause trekking, to form a winding loop in the heating materials, and to cause short circuit in the heated materials. For the positive temperature line, if the middle is shorted, the current continues to flow to the short circuit unless the breaker disconnects. Consequently, a heated fire that does not cut off the power immediately may leave multiple marks or cuts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.738-742
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• 2006

In this study we developed the electrical heating mold core by applying three different heating methods. In order to find out the optimal heating method, we observed the temperature profiles with time. We also injection-molded the parts by the heating methods and investigated the shrinkage ratio, density, surface roughness and weld-lines. The temperature rise time and cycle time showed the promising results for commercial applications(the rise time is $130^{\circ}C$/14sec, the cycle time is 55sec). By comparing with the conventional and gas flame heating method, the parts by this method were proven to have good qualities. The shrinkage ratio reduced by 5.1%, the density increase by 2.66%, the smoothness increased about 3 times, and the weld-line did not observed by naked eyes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.35-41
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• 2008

Qualitative enhancement of dwelling life has changing the recognition for the environment friendly wood which is being highlighted for its usage as an interior materials. This trend may prove the excellent performance of wood whose inherent characteristics has its comfortable, mild feeling of material, sound resistance and stabilities and the market of interior woods including floor, moulding and wooden panel as finishing interior materials is growing sustainably. However, since this materials is vulnerable to humidity and flame, waterproofing and flame retarding stability, an essential condition for interior materials, together with maintenance, are the main topics to be resolved. From the above-mentioned results, as a result of waterdrop contact angle, wood absorption volume and water content percentage test and the performance test of the processed materials after flame retardant, though there was some submerging time changes among types of woods for ensuring waterproofing performance improvement but as time passes, similar tendency was noticed to be formulated. As the submerging time is increased, so does the absorption volume and accordingly optimal level of range is judged to be drawn in order to ensure excellent performance, taking optimal economy into consideration. Therefore, it is considered that above-mentioned woods could be utilized for waterproof and flame retardant processed interior materials using uniform microwave and in order to put this technology into practical application, a research by way of diversified performance proving is required to be carried out.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1033-1040
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• 2011

The premixed burner is a very strong candidate for using household boiler burner system because it has high efficiency, low emission and can be used in compact boiler system. Usually, household boiler burner systems use a Bunsen burner, which consists of an inner rich premixed flame and fuel burned completely by a secondary air supply. It has a relatively long flame length and operates in a high excess of air, so it is difficult to fit such a burner into a high efficiency compact boiler. In this paper, the characteristics of a premixed combustion burner for surface media such as metal fiber, ceramic, and SUS fin were evaluated. In particular, the flow velocity over the burner surface for the cold flow characteristics of the surface material were measured and adjusted. The combustion tests were carried out by taking pictures of the flame and measuring the flame temperature. The amounts of CO and NO were measured and the characteristics of the surface burner materials, combustion chamber, and heat exchangers were evaluated for various excess air ratios and heating values.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1140-1145
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• 2004

Laser-induced incandescence (LII) is introduced as a valuable tool for the characterization of nanoparticles in flame environments. This technique is based on the heating of the particles by a short laser pulse and the subsequent detection of the thermal radiation. It has been applied successfully for the investigation of soot in different fields of application. The evaluation of the temporal decay of the laser-induced incandescence (LII) signal from soot particles is introduced as a technique to obtain two-dimensional distributions of particle sizes and is applied to a laminar diffusion flame. This novel approach to soot sizing exhibits several theoretical and technical advantages compared with the established combination of elastic scattering and LII, especially as it yields absolute sizes of primary particles without requiring calibration. With this technique a spatially resolved 2-D measurement of soot primary particle sizes is feasible in a combination process form the ratio of emission signals obtained at two delay times after a laser pulse, as the cooling behavior is characteristic of particle size.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.187-192
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• 2008

A simplified model for an isolated aluminum particle burning in air is presented. Burning process consists of two stages, ignition and quasi-steady combustion (QSC). In ignition stage, aluminum which is inside of oxide film melts owing to the self heating called heterogeneous surface reaction (HSR) as well as the convective and radiative heat transfer from ambient air until the particle temperature reaches melting point of oxide film. In combustion stage, gas phase reaction occurs, and quasi-steady diffusion flame is assumed. For simplicity, 1-dimesional spherical symmetric condition and flame sheet assumption are also used. Extended conserved scalar formulations and modified Shvab-Zeldovich functions are used that account for the deposition of metal oxide on the surface of the molten aluminum. Using developed model, time variation of particle temperature, masses of molten aluminum and deposited oxide are predicted. Burning rate, flame radius and temperature are also calculated, and compared with some experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.159-165
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• 1999

Experimental studies have been performed to observe the basic phenomena of waste bed combustion in MSW incinerator. A reduced scale apparatus was utilized to simulate the combustion behavior in real plant with 1-dimensional transient behavior at the experimental setup, which uses wet cubic wood with ash content as simulated waste. LHV (lower heating value) of solid fuel, fuel particle size and flow rate of combustion air were taken as important parameters of the bed combustion. For the quantitative analysis, FPR (flame propagation rate), TBT (total burn-out time) and PBT (particle burn-out time) was defined. LHV represent the capability of heat release of the fuel, so that a higher LHV results in faster reaction rate of the fuel bed, which is shown by higher FPR. Fuel particle size is related with surface area per unit mass as well as heat and mass transfer coefficient. As the particle size increases the FPR decreases owing to decreasing specific surface area. Air injection supplies oxygen to the reaction zone. However oversupply of combustion air increases convection cooling of the bed and possibly extinguishes the flame.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.1
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• pp.99-108
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• 2004

Fundamental combustion characteristics, such as the combustion potential, burning velocity and flame stability, for the practical utilization of LFG(Landfill gas) and LFG-blended fuels were experimentally investigated. The combustion potentials(CP) of LFG-blended fuels calculated from the previously suggested formulae were compared with burning velocities obtained by present experiments. The results showed that the previous formulae fur CP of LFG-blended fuels were not agreed with the experimental burning velocity, and these formulae should be revised. To provide an useful information needed to design the combustion devices, a triangular diagram was suggested for the maximum burning velocity of the mixture of CH$_4$, LPG and LFG. From the investigation of the burning velocity and the flame stability in a practical combustor, it was noted that the LFG-blended fuels, of which heating values or Wobbe indices were adjusted to that of natural gas, could be used as an alternative fuel of natural gas.