• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 2003.05a
• /
• pp.303-308
• /
• 2003

가연성 물질의 최소점화에너지(Minimum Ignition Energy; MIE)를 아는 것은 화학공정 등의 안전성 평가에 중요한 것이다. 현재 MIE의 측정에는 주로 용량성 불꽃방전이 이용되고 있다. 용량이 큰 커패시터를 이용한 방전에서는 MIE가 크게 되는 경향이 있고, MIE가 회로정수에 의존한다는 것이 실험적으로 알려져 있다. 이 현상은 방전회로의 시정수와 점화를 위한 에너지의 수송시간과의 관계에 의해 이론적으로 설명하는 것이 가능하게 되었다.(중략)

• Transactions of the Korean hydrogen and new energy society
• /
• v.24 no.6
• /
• pp.573-579
• /
• 2013

Hydrogen engine with homogeneous charged compression ignition can achieve high efficiency by high compression ratio and rapid chemical reaction rates spatially. However, it needs to expansion of the operation range with over-all load conditions which is very narrow due to extremely high pressure rise rate. The adoption of the lean boosting in a HCCI $H_2$ engine is expected to be effective in expansion of operation range since minimum compression ratio for spontaneous ignition is decreased by low temperature combustion and increased surround in-cylinder pressure. In order to grasp its possibility by using lean boosting in the HCCI $H_2$ engine, compression ratio required for spontaneous ignition, expansion degree of the operation range and over-all engine performance are experimentally analyzed with the boosting pressure and supply energy. As the results, it is found that minimum compression ratio for spontaneous ignition is down to the compression ratio(${\varepsilon}$=19) of conventional diesel engine due to decreased self-ignition temperature, and operation range is extended to 170% in term of the equivalence ratio and 12 times in term of the supply energy than that of naturally aspirated type. Though indicated thermal efficiency is decreased by reduced compression ratio, it is over at least 46%.

• Fire Science and Engineering
• /
• v.18 no.1
• /
• pp.18-23
• /
• 2004

This paper describes the minimum ignition limits for propane-air 5.25 Vol.% mixture gases in low voltage inductive circiuts. The improved effects on the ignition limit are studied by parallel safety components(resistors) for propane-air 5.25 Vol.% mixture gas in low voltage inductive circuits. The experimental devices used in this test are the IEC type spark ignition test apparatus. The minimum ignition limits are controlled by the values of current in inductive circuit. Energy supplied from electric source is first accumulated at the inductance, it's extra energy is working as ignition source of the explosive gas. The improved effects on the ignition limit are respectively obtained as the maximum rising rate of 330% by composing parallel circuits between inductance and resistor as compared with disconnecting inductance with the safety components. The more values of inductance increase the higher improved effects of ignition limit rise. The less values of resistor the higher improved effects of ignition limit rise. It is considered that the result can be used for not only data for researches and development of intrinsically safe explosion-proof machines which are applied equipment and detectors used in dangerous areas but also for datum for its equipment tests.

• Korean Chemical Engineering Research
• /
• v.55 no.5
• /
• pp.623-628
• /
• 2017

Using wood pellets, which are used as fuel for thermal power generation plants, as test specimens, the minimum spontaneous ignition temperatures according to the size of the container for the test specimens were measured, and by applying the Frank-Kamenetskii theories on thermal energy to these temperatures, the danger factor of the materials were calculated by deriving the apparent activation energies. The results confirmed that the ignition threshold temperature decreased as the size of the container increased and that the spontaneous ignition energy was 37.83 kcal/mol. The results also confirmed that the larger the container for the test specimens was the time to arrive at the spontaneous ignition time and maximum temperature also increased.

• Journal of the Korean Society of Safety
• /
• v.33 no.2
• /
• pp.39-44
• /
• 2018

Dust explosions are occurring in a variety of industries. A dust explosion caused by a specific energy generates huge amount of energy in the ignition and releases decomposition gas. Damages can be increased since this released decomposition gas can cause second and subsequent explosions. In this study, the goal was to obtain practical information on what could affect the explosion by comparing the characteristics of two kinds of dusts with completely different chemical properties. Three kinds of dusts were measured and evaluated for explosion pressure, dust explosion index, explosion limit and minimum ignition energy. It is possible to grasp the characteristics of each dust and use it as useful accident prevention data in the production of raw material powder.

• Journal of the Korean Society of Safety
• /
• v.25 no.5
• /
• pp.22-26
• /
• 2010

The ignitability(minimum ignition energy, MIE) of a suspended dust clouds is very important aspect of technical safety indices. This paper reported the experimental results dealing with the influence of discharge circuit on the MIE of a suspended dust clouds. The movement of a suspended dust clouds was also observed with the high speed camera. The Hartmann vertical-tube apparatus(MIKE-3) described in the international standard of IEC and Polypropylene (PP, 50% volume-average, D50: $761{\mu}m$) resin powders were used in this experiment. The following results were obtained: (1) the MIE of a suspended PP powder depended markedly on the discharge circuit; in other words, when a resistor was connected in series with the discharge sparking circuit(RC), the lowest value(31mJ) of MIE was obtained for a suspended PP powder comparison with the other circuits(C circuit; 370mJ or LC circuit; 71mJ). (2) the discharge duration time is more important than other factors with regard to MIE of a suspended PP powder.

• Fire Science and Engineering
• /
• v.33 no.1
• /
• pp.7-14
• /
• 2019

While wood pellets are often used as a fuel in thermoelectric power plants and firewood boilers, there is a risk of ignition temperature when strong wood pellets, which have a high calorific value, for prolonged periods of time. In this research study, the minimum auto ignition temperature and the ignition limitation temperature according to the change in flow rate depending on the size of the test vessel were calculated, and based on these temperatures, the apparent activation energy was calculated to predict the combustive properties of the material. The apparent activation energy was calculated to be 190.224 kJ/mol. The thicker the sample is storage in the vessel, the longer the ignition induction time was due to the increased difficulty in heat being transferred from the surface of the vessel to the middle section area of the vessel. For vessel of the same size, the higher the flow rate, the lower the auto ignition temperature was. It was also confirmed that increases in the size of the test vessel lowered the auto ignition temperature and increased the ignition induction time.

• Journal of the Korean Society of Safety
• /
• v.15 no.4
• /
• pp.95-100
• /
• 2000

This study was performed in Hartmann type dust explosion apparatus in order to research the dust explosion characteristics of hydroxypropyl methyl cellulose(HPMC): minimum explosive limit, minimum ignition energy, limiting oxygen concentration, maximum explosion pressure, rate of pressure rise, etc. The samples of HPMC dust were distributed into 120-140 mesh, 170-230 mesh and 325 under, and the gap distance of the discharge electrode was setted up at 5mm. The experimental results were obtained as follows: (1) The minimum explosive limit for HPMC dust was founded at 180g/㎥. the minimum ignition energy at 9.8mJ and the limiting oxygen concentration at 12%. (2) The maximum explosion pressure of HPMC dust was $8.1kg/cm^2\;{\cdot}\;$abs at the concentration of $500g/m^3$ and the maximum rate of pressure rise was 203.98 bar/sec at the concentration of $480g/m^3$ for 325 under.

• Journal of the Korean Society of Safety
• /
• v.7 no.4
• /
• pp.45-53
• /
• 1992

Sponataneous ignition characteristics for granulated activated carbon were observed by performing experiments at constant ambient temperature and varying the ambient temperature sinusoidally. In case of varying the ambient temperature sinusoidally, the amplitudes of temperature were 5$^{\circ}C$, 1$0^{\circ}C$ and 15$^{\circ}C$ respectively, and the period in each amplitude was varied at an interval of 30minutes from zero to 3hours. As the results of experiments at a constant ambient temperature, the critical spontaneous ignition temperature of the sample decreased as the sample vessel size increased. Apparent activation energy of the sample calculated from the Frank-Kamenetskii's thermal Ignition theory was 38.82［kca1/mo1］ In case of varying the ambient temperature sinusoidally, the critical spontaneous ignition tempera-ture was lower than that at the constant ambient temperature, and the minimum critical spontaneous ignition temperature decreased with the amplitude of heating sinusoidal curve. At the same amplitude, the critical spontaneous ignition temperature decreased until it reached the minimum point and then in-creased as the period increased.

• Proceedings of the KIEE Conference
• /
• 1996.07c
• /
• pp.1854-1856
• /
• 1996

This study describes the minimum ignition limit for LPG-Ai-r mixtures by switching sparks in radio-frequency limits using RF power supply and IEC type ignition spark apparatus. As a result, the minimum ignition limit voltage is increased in proportional to the rate of increasing of frequency in LPG-Air mixed gas. Especially, increment between 10[kHz] and 30[kHz] is typical. It is considered that ignition is caused by one discharge until 10 [kHz] and, beyond 10[kHz] ignition is caused by more than two discharges. The reason is analysed that energy loss is caused by existing pause interval between discharges.