• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.41-46
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• 2011

We investigated experimentally the properties of dust explosion through lycopodium particle clouds in a duct to provide the fundamental knowledge. Propagating dust flames in the vertical duct of 120 cm height and 12 cm square cross-section were observed by digital video camera and flame front is visualized using by PIV(Particle Image Velocimetry) system. As the result, when the same average dust concentration existed in the vertical duct, downward flame propagation was faster than the upward flame propagation, its rate increased with dust concentration in 300g/$m^3$. Post flames were caused by the ignition of unburned particles which flowed into the rear region of flame from passage between flame and duct wall, and they generated regardless of duct condition. Also, it was found that appearance frequency of post flames during dust flame propagations increased with the increase of dust concentration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.593-602
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• 1999

This paper presents combustion characteristics of LPG-air mixture ignited by the plasma jet in a cylindrical vessel with constant volume, in which our focus is placed on the multi-hole plug configuration. Four types of the plug configuration depending on the number of orifice and the arranged angle are considered, along with two cases of conventional spark ignition for comparison. Not only the flame propagation is photographed at intervals, but the pressure in the combustion chamber is also recorded through the entire combustion process. The results show that the plasma jet ignition enhances the overall combustion rate remarkably in comparison to the spark ignition by generating irregular flame front and penetrating through the unburned mixture. The combustion enhancement rate agrees favorably with the available data, which supports the validity of our experiment. Synthetically estimating, the two-hole sixty-degree plug appears to be the most desirable, in that the maximum pressure as well as the combustion duration is less affected by the sub-energy level than the others. It is also deduced that there may exist an optimal plug configuration capable of rapid combustion for a specific combustion chamber.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.68-74
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• 2008

Measurements were performed to investigate the effects on flame and pressure development by varying locations of multiple obstacles in a top-venting explosion chamber. The chamber dimension was 1000 mm in height with a $700\;{\times}\;700\;mm^2$ cross-section and a rectangular vent area of $700\;{\times}\;700\;mm^2$. Three different multiple obstacles with blockage ratio of 30% were used by changing from 200 mm, 500 mm to 800 mm in heights within the chamber. Temporally resolved flame front images were recorded by a high speed camera to investigate the interaction between the propagating flame and the obstacles. The results showed that the triangular bar caused the fastest flame developments at given times whereas the lowest was obtained with the cylindrical bar. It was also found that local flame displacement speeds of different obstacles were sensitive to the locations of obstacles. The local speed becomes larger in going from 200 mm, to 500 mm and to 800 mm in heights. The obstacles in height of 800 mm yielded the highest overpressure whereas the lowest was in height of 200 mm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.309-319
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• 2011

We experimentally investigated lifted propane jet flames diluted with nitrogen to obtain flame-stability maps based on heat-loss-induced self-excitation. We found that heat-loss-induced self-excitations are caused by conductive heat loss from premixed flame branches to trailing diffusion flames as well as soot radiation. The conductive-heat-loss-induced self-excitation at frequencies less than 0.1 Hz is explained well by a suggested mechanism, whereas the oscillation of the soot region induces a self-excitation of lift-off height of the order of 0.1 Hz. The suggested mechanism is also verified from additive experiments in a room at constant temperature and humidity. The heat-loss-induced self-excitation is explained by the Strouhal numbers as a function of the relevant parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.996-999
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• 2011

The flow and combustion dynamics in the ignition and ramjet sustainer phase of an integrated rocket-ramjet(IRR) engine are investigated. The physical model includes the entire engine flowpath, from the freestream in front of the inlet to the exit of the exhaust nozzle. The flowfield obtained from a rocket booster study is used as the initial condition for the present analysis, so that the complete operation history of the engine can be obtained. The analysis for the primary factor governing flame propagation during the ignition and the key mechanisms for driving and sustaining the flow oscillations are performed.