• Fire Science and Engineering
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• v.34 no.4
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• pp.101-106
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• 2020

This study analyzed flame growth characteristics and carbonization patterns when floor materials were burned vertically using a needle flame produced for this study. It was found that PVC flooring was fire retardant and the area under direct flame contracted inward. Vertical combustion causes solidification in the form of a lump at the bottom and also generates soot in a pattern that progresses upwards. This study found that laminated flooring exhibited no fire retarding characteristics and that the laminated layer of its upper surface was destroyed by fire, causing irregular delamination. The carbonization ranges at the left and right sides were determined to be symmetrical. A vertical combustion test of a sample carpet showed that it exhibited no fire-retarding characteristics. It was observed that if heat accumulated in the carpet, the flame formed an ascending air current, and that when flammable materials were present around the flame, they further accelerated the diffusion of the flame. The carbonization pattern at the carpet surface exposed to direct flame revealed that the carpet surface had melted and had flown downwards and that many tiny holes formed on it.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.8
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• pp.83-89
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• 2013

In this paper, discharge characteristics of air in the vertical arrangement of three rods(dome-shaped, cylinder-shaped, and needle-shaped rod) and plane gap having propane flame on the plane electrode are examined under the application of a.c. and d.c. high-voltages. As the result of the experiment, flashover voltages in the presence of the flame are substantially lowered than those in the absence of flame, and relative a.c. flashover voltages in the dome-shaped, cylinder-shaped, and needle-shaped rod gaps are found 32.5%, 32.1%, and 26.4% respectively. The polarity effects with the d.c. voltages are shown, and flashover voltages in negative polarity are much lowered than those in positive one. The negative flashover voltages in the dome-shaped and cylinder-shaped gaps are found 18.3% and 18.7% respectively, but the positive ones are found 53.5% and 43.2% respectively. In the needle-shaped rod gaps, meanwhile, the flame is extinguished by corona wind, and the quenching voltages are found 28.4% under the application of a.c. voltages. The ion winds of corona and the reduction of air density are the main factors of flashover reduction owing to the flame in the case of a.c. voltages, but the electrifications of the positive ion by thermal ionization besides the above factors are remarkably found in the case of d.c. voltages.

• 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.

• Fire Science and Engineering
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• v.17 no.2
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• pp.25-34
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• 2003

In this paper, characteristics of the DC flashover voltage in the horizontal air gap of sphere-sphere/needle-needle electrode system were investigated when the combustion flame of paraffin oil was present between the two electrodes. The reduction characteristic of DC flashover voltage was discussed with the thermal ionization process, the relative air density and the deflection phenomena in the shape of flames that caused by the corona wind and Coulomb's force. As the results of an experimental investigation, It was found that the reduction characteristics of DC flashover voltages with flames were affected strongly by the flame deflection and the change of relative air density. It was also found that the thermal ionization phenomena were not important in the range of combustion flame temperature.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.193-197
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• 2001

In this paper, reduction characteristics of the ac flashover voltage in the horizontal air gap of sphere-sphere and needle-needle electrode system were investigated when the combustion flame was present near the high-voltage electrodes. The reduction characteristics of ac flashover voltage were discussed with 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, It was found that the reduction of flashover voltage 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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.152-159
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• 2010

A combustion flame under the overhead power lines may be caused by breakdown disturbances in power systems. In this study, experiments were conducted for the purpose of investigating the reduction in insulation strength caused by combustion flame and the shape changes of the flame, and flashover characteristics and extinction phenomena of the flame in the simulated conditions of overhead power lines were examined under the application of a.c. and d.c. high-voltages. As the results of the experimental investigation, it is demonstrated that flame can remarkably reduce breakdown voltages of the air-gap in shorter range of the gap distance. As the gap distance increases, flame was quenched, before the flashover, by corona wind generated from the needle electrodes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.819-827
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• 1987

The purpose of the present investigation is to examine the effect of water addition on combustion efficieny. In this research, fuel and additive water are injected into a burner in the form of vapors through separate needle valves, the flame temperature and concentrations of soot, CO and unburned hydrocarbons were measured in a premixed flame. The results are obtained to be: In the fuel lean region, the reduction rate of CO, soot and HC by water injection increases slightly, but there is no change in the combustion efficiency. On the other hand, in the fuel rich region, the reduction rate of CO, Soot and HC by water injection increases more than that of the fuel lean region. Accordingly, combustion efficiency increases.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.27-34
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• 2002

In this paper, characteristics of the ac and dc flashover voltage in the horizontal air gap of a needle-needle electrode system were investigated when the combustion flame was present near the high-voltage electrode. In order to examine the flashover phenomena and the corona inception voltages caused by flame we measured the voltage and current waveforms when the corona and the flashover was occurred. We also observed, as increasing the applied voltages, the deflection or fluctuation phenomena in the shape of flames caused by the corona wind and the coulomb's force. As the results of an experimental investigation, we found that the reduction of flashover voltages, in comparison with the no-flame case, are 62.7[%] for k=1.0, 34.2[%] for h=5[cm], 27.3[%] for h=7[cm] and 21.4[%] for h=9[cm] when ac voltage is applied.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1735-1737
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• 2001

The occurrence of fires under transmission lines is responsible for a great number of power line outages. In this paper, the ac flashover voltages and the corona onset voltages of a needle-plane electrode gap of vertical arrangement in the presence of flame were investigated. We also observed the corona discharge current and variation of shapes in flame with increasing the applied voltages. We found that the corona onset voltages and the flashover voltages were drastically decreased with the position of flames and gap length of electrodes, and observed that the deflection or fluctuation phenomena in the shape of flames.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.103-110
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• 1998

This experiment is performed to investigate the effects of the emulsion on the flame temperature and soot formation in a diesel engine. The two-color method is used to measure the flame temperature for combustion of emulsified diesel in the Rapid Compression and Expansion Machine(RCEM). The concentration of soot is estimated via calculation of the KL factor. The solenoid valve, elecronic controller and needle lift sensor are used to control the exact injection timing and duration under various operating conditions. According to the results the soot concentration is reduced with the increasing W/O while the temperature reduced. The pressure data and the flame images captured by a high speed camera show that the ignition delay of emulsified diesel increase the duration of premixed combustion. The sizes of water drops are measured to be about 10${\mu}m$ by a microscope.