• Fire Science and Engineering
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• v.23 no.5
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• pp.84-89
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• 2009

In this study, the fire extinguishing experiment was performed using a water mist nozzle with variation of factors which affect on the extinguishing time. The variables were distance from nozzle center to fire location, droplet size, height of nozzle and opening or not. With the experimental data, interaction and sensitivity between factors were analysed with Mini tab and deduce a optimum model of fire extinguishing of water mist system. Based on the experiment and modeling of fire extinguishing with water mist system, the most important factor on extinguishing time is the distance from the center of nozzle to fire and the opening effect was small compare with other factors.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.717-725
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• 1989

An experimental investigation on the combustion behavior of pulverized coal particles was performed using the cross-section micrography techniques while sample coal particles were collected in-situ from the flow reactor. The coal particles were representative of pulverized bituminous coal undergoing a raped pyrolysis and combustion, however, quenched at the time when the particles were deposited onto a sample plate. The internal structure of coal was observed to change as deposited. Upon injection into a flow reactor, bituminous coal particles showed many holes which represented internal pore formation during the pyrolysis. The relative portion of the remaining matrix of coal was decreasing as the residence time progressed. This direct observation of cross-section of burning particles enabled better understanding of the coal combustion behavior.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.349-354
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• 2002

쌀 소비량은 생활 수준 향상과 외식 및 식품 산업의 발달로 감소하고, 고품질 쌀을 요구하는 성향이 높아지고 있다. 현재, 고품질 쌀을 생산할 수 있는 기술과 제반 요건은 구비되어 있으나, 수확 후 건조·저장 중에 쌀의 품질이 저하된다. 특히 건조 중 품질 저하는 고온건조에 의한 동할 발생 및 과건조가 주요 원인이다. 이를 해결하기 위해 원적외선 건조 시스템에 관한 연구가 진행 중이다. 본 연구에서는 방사율이 높고, 접착성 및 내열성 등이 강한 곡물 건조기용 방사체 코팅원료를 개발하고, 이 원료를 원적외선 방사체에 코팅한 후 방사체의 형태와 크기에 따라 표면 온도 분포 및 연료 소비량 등을 측정 분석하여 방사체의 특성과 적정 조건을 규명하고자 하였다. 연구 결과를 요약하면 다음과 같다. (1) 세라믹 코팅 원료의 배합비는 세라믹분말 40%와 결합재 60%가 접착력과 가열경화 후 표면이 양호한 것으로 나타났다. (2) 노즐의 유량 및 분무각에 따른 버너의 화염길이 및 폭은 노즐유량이 증가함에 따라 증가하는 경향을 나타내었다. (3) 방사체 위치별 표면온도편차는 방사체 길이가 1350mm인 것이 작은 것으로 나타났고, 열풍유동관 직경이 Rounding type의 경우 76.3mm, Right angle type의 경우 89.1mm일 때 표면 온도편차가 적었다. (4) 연료소비량은 열 풍유동관 직경이 클수록, 방사체 길이가 길수록 증가하는 경향을 나타내었고, Right angle type이 Rounding type에 비하여 연료소비량이 약간 높은 것으로 나타났다.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.1-8
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• 2013

This study presents relations between the time lag and interaction index of the impinging-jet injectors using the time lag model in a model chamber. The response of the flame is analyzed to artificial perturbation with 5% amplitude of oxidizer speed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. In this method, time lag or delay is calculated by the characteristic length and the average velocity obtained from numerical results. The tendency that the time delay decreases with axial jet velocity has been observed.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.72-79
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• 2018

An experimental study was performed to investigate the chemiluminescence characteristics in the spray combustion of ultransonically atomized kerosene. The radical intensity of the spray flame was measured using an ICCD camera and the amount of fuel consumed was obtained by a precise flow-rate measurement technique during combustion. Fuel consumption increased linearly with the increase in carrier-gas flow rate, and typical group combustion, which is a characteristic of spray combustion, was observed. It was found from the analysis of chemiluminescence that the maximum emission intensities of OH and CH radicals decrease, and they move downstream resulting in the increase in a vivid reaction zone as the spray flow rate increases.

• Fire Science and Engineering
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• v.31 no.5
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• pp.53-62
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• 2017

Electric power which is the energy source of economy and industries requires long distance transportation due to regional difference between its production and consumption, and it is supplied through the multi-loop transmission and distribution system. Prior to its actual use, electric power flows through several transformations by voltage transformers in substations depending on the characteristics of each usage, and a transformer has the structure consisting of the main body, winding wire, insulating oil and bushings. A transformer fire that breaks out in substations entails the primary damage that interrupts the power supply to houses and commercial facilities and causes various safety accidents as well as the secondary economic losses. It is considered that causes of such fire include the leak of insulating oil resulting from the destruction of bottom part of bushings, and the chain reaction of fire due to insulating oil that reaches its ignition point within 1 second. The smoke detector and automatic fire extinguishing system are established in order to minimize fire damage, but a difficulty in securing golden time for extinguishing fire due to delay in the operation of detector and release of gas from the extinguishing system has become a problem. Accordingly, this study was carried out according to needs of active mechanism to prevent the spread of fire and block the leak of insulating oil, in accordance with the importance of securing golden time in extinguishing a fire in its early stage. A bushings fireproof structure was developed by applying the high temperature shape retention materials, which are expanded by flame, and mechanical flame cutoff devices. The bushings fireproof structure was installed on the transformer model produced by applying the actual standards of bushings and flange, and the full scale fire test was carried out. It was confirmed that the bushings fireproof structure operated at accurate position and height within 3 seconds from the flame initiation. It is considered that it could block the spread of flame effectively in the event of actual transformer fire.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.409-416
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• 2010

The use of oxy-fuel combustion and flue gas recirculation (FGR) for $CO_2$ reduction has been studied by many researchers. This study focused on the characteristics of oxy-fuel combustion and the effects of $CO_2$ addition from the point of view of oxygen feeding ratio (OFR) and the position of $CO_2$ addition in order to reproduce an FGR system with a triple concentric multi-jet burner. Oxy-fuel combustion was stable at all OFRs at a fuel flow-rate of 15 lpm, which corresponds to an equivalence ratio of 0.93; however, the structure and length of the flame varied at different OFRs. When $CO_2$ was added in oxy-fuel combustion, various stability modes such as stable, transient, quasistable, unstable, and blow-out were observed. The temperature in the combustion chamber decreased upon $CO_2$ addition in all conditions, and the maximum reduction in temperature was below 1800 K. $CO_2$ concentration with respect to height varied with the volume percent of $CO_2$ at the nozzle tip.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1427-1430
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• 2014

A thermal barrier coating (TBC) prevents heat directly transferring from a high-temperature flame to a substrate. The TBC system comprises a top coating and bond coating. TBC technology reduces the substrate surface temperature by about $100{\sim}170^{\circ}C$. In the TBC system, internal stress is generated by the difference in thermal expansion coefficients of the substrate and coating. The internal stress also differs according to the shape and position of the blade. In this study, finite element analysis was performed for different curvatures of coin-shaped specimens, which are commonly used for thermal fatigue tests, and the changes in internal stress of the TBC system were compared. Based on the results, the curvature at which the minimum stress occurs was derived, and the thermal stress was confirmed to increase with the difference between a given curvature and the curvature with the minimum stress.

• Journal of the Society of Disaster Information
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• v.16 no.2
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• pp.383-391
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• 2020

Purpose: To identify internal self ignition and ignition caused by external flames in energy storage rooms, and to analyze the difference between ignition due to overheating and ignition caused by external heat sources. Method: membrane melting point measurement, battery external hydrothermal experiment, battery overcharge experiment, comparative analysis of electrode plate during combustion by overcharge and external heat, overcharge combustion characteristics, external hydrothermal fire combustion characteristics, 3.4 (electrode plate comparison) / 3.5 (overcharge) /3.6 (external sequence) analysis experiment. Result: Since the temperature difference was very different depending on the position of the sensor until the fire occurred, it is judged that two temperature sensors per module are not enough to prevent the fire through temperature control in advance. Conclusion: The short circuit acts as an ignition source and ignites the mixed gas, causing a gas explosion. The electrode breaks finely due to the explosion pressure, and the powder-like lithium oxide is sparked like a firecracker by the flame reaction.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.1-6
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• 1997

In case of using the electrical apparatus in the hazardous atmosphere which exist flammable gas mixtures, There is a dangerosity of gas explosion accident by the electrical spark. The most general method to prevent the explosion by the spark is to use the flame-proof type electrical apparatus to isolate the ignition source. from the flammable atmosphere. But actualy it is impossible to isolate the ignition sources from the atmosphere. So it was needed to find the safe gap which prevent ignition of flammable atmosphere by transmission of flame or heat when a flammable gas mixture exploded inside the apparatus. In this study we tried to find the maximum experimental safe gap(MESG) of $H_2$-air, and $CH_4$-air mixtures by using the 8 litre spherical vessel with 25mm flange. The experiment parameter were ignition position, concentration and initial pressure before explosion. From the experiment the ignition position was affected to the MESG. MESG value was minimum near the stoichiometric concentration of gas mixtures, and according to the increase of initial pressure MESG was decreased.