• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.153-159
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• 2007

The performance of a direct-injection type diesel engine often depends on the strength of air flow in the cylinder, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the process of combustion in the cylinder was affected by the mixture formation process. In the present paper, high speed photography was employed to investigate the effectiveness of holes penetrated from the bottom of cavity wall to piston crown for some more useful utilization of air. The holes would function to improve mixing of fuel and air by the increase of air flow in the cylinder. The results obtained are summarized as follows, (1) Activated first of the combustion by shorten of ignition timing and rapid flame propagation (2) Raised the combustion peak pressure, more close to TDC the formation timing of peak pressure.

• Journal of the Korean Society of Combustion
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• v.12 no.1
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• pp.11-20
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• 2007

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Different shock tube fill pressures have various inflow conditions. $15^{\circ}$ inclined hydrogen fuel injection is located before the cavity. Oblique shock is generated from the cavity and reflects off the top and bottom wall. For non-reacting flow, fuel makes the shear layer thicker above the cavity therefore, the shock is generated just before the trailing edge. This research has self-ignition in the combustor. For reacting flow, as the equivalence ratio increases, flame starts to generate near the injector or occur in the recirculation zone before the injector. High fuel injection sustains the jet shape in the cross flow and air can mix with fuel along the shear layer. Therefore, two flame layers find above the cavity for high equivalence ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.328-331
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• 2008

In order to see the detailed characteristics of model scramjet engine, numerical analysis was performed and compared to the ground test results done by KARI and UQ. Pressure distribution predicted by numerical analysis showed good agreements with test results. Static temperature and pressure distribution explained the mechanisms of cavity flame holder and W-shape cowl which have showed enhancing effects on the supersonic combustion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.3
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• pp.257-262
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• 1983

The performance of a direct-injection type diesel engine often depends on the shape of combustion chamber, strength of swirl or squish, the number of nozzle holes, etc. This is of course because the process of combustion in the cylinder was affected by the mixture formation process. In this paper, the relation betweeen the flame progress and the performance of engine was clarified by changing variously the combustion process in cylinder with a special method, and thus the measures for improving the combustion were indirectly examined. Namely it was investigated what effect the flame progress in cylinder, which was varied with the locality of the lean premixture injected by the auxiliary injection method using an auxiliary injection nozzle in advance at the place where main spray was injected later, has on the engine output, the exhaust smoke density and the NO concentration in exhaust gas.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.320-330
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• 1999

A numerical study was performed to investigate spray behavior and its interaction with air flow in a flame holding region of an oil burner(0.1MW) using the KIVA3 code. The numerical results in shape of the recirculating flow and size of the recirculation zone under different conditions were compared to those experimental results. The numerical results in fuel droplet trajectory show that a droplet under 30${\mu}m$ can follow the air flow but a droplet over 50${\mu}m$ penetrates the recirculation zone due to large momentum and a droplet of 30-50${\mu}m$ can follow the recirculating flow or pene-trates the recirculation zone.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.43-46
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• 2012

The oxygen concentration of primary oxidizer is decided under 10% due to flammable risk. It can be a spontaneous combustion inside burner or tube if the excess oxygen is added to primary oxidizer in Oxy-PC burner. In this case, the rest oxygen which can not be injected to primary oxidizer should be injected to another port. If added it to a second oxidizer, the ignition is unstable at outlet of burner. Accordingly an extra lancing port is needed to insert into the burner unlike other common air mode. And the flame formation and combustion characteristic differ from lancing port position. Therefore we observed flame formation which has stable combustion characteristic according to the shape and position of lancing port.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.71-79
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• 2002

The characteristics of the catalytically supported combustion with Pd and Pd/Pt based catalyst using the bench-scaled high pressure combustor have been investigated up to 5atm. This study aimed to investigate combustion characteristics of the stable flame attached to the exit of catalyst bed and NOx emissions with respect to the position of axial and radial direction in the combustor. NOx emissions were increased along the axial distance after the catalyst bed exit and radially decreased from the center to the wall of the combustor. At the higher pressure, the NOx emission decreased slightly due to the lower flame temperature in the combustor at the high pressure.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.231-235
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• 2002

A theoretical and experimental study on the combustion process in a constant volume micro combustor is described. Unlike in a macro scale constant volume combustor, the heat loss to the wall plays a major role in flame propagation in a micro micro combustor. In order to analyze the effect of heat loss on combustion phenomena, pressure transition from ignition was measured. A number of cylindrical micro combustors with different diameter and depth were used for experiment to study the effect of length scales and shape factor. The diameter of combustor ranged from 7.5mm to 22.5 mm and the height of cylinder was from 1mm to 4mm. Initial pressure was also varied for the experiment. The diagnostic methods were severely limited due to the size of the apparatus and uncertainties of certain quantities to be measured in a small-scale environment. An analytical method to derive physical quantities that are essential for performance prediction from the pressure measurements is described.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.157-163
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• 2006

A new technique utilizing LII signal for the measurement of flow velocities of laminar diffusion flames has been investigated. Soot particles in ethylene diffusion flames are heated by a modulated Ar-ion laser beam. LII signals and their phase angles are measured using a lock-in amplifier at the different flame heights and the axial flow velocity are obtained from the measured phase angle delay. The measured velocities are similar to those from LDV measurements under the same operating conditions. The effects of laser power, LII signal wavelength, and modulation frequency are not sensitive to the velocity measurement. However, the choice of an optical chopper blade type could affect the measurement result. The use of a 6/5 chopper blade showed the better result that is possibly due to the square shape of modulated laser beam. This study successfully demonstrated that axial flow velocities of laminar diffusion flames can be measured by a new technique utilizing LII signal, which does not need particle seeding unlikely to LDV or PIV techniques.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.327-334
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• 1997

In many large urban-fire scenarios one of the critical issues is to attempt to protect the lives of fire fighters in helicopters deployed to flying over the fires and also the lives of people trapped in open areas downwind of the fires such as in parks. The strategies of such protection measures depend significantly on our knowledge of the size and extent of such fires as affected by the prevailing winds. In this study, the shape or profile of the fire plume typical of large urban fires, as affected by a steady unidirectional wind with or without imposing a shear flow on the fire plume, has been simulated numerically by a field model. The results show that the simulations provide realistic flame profiles and at least qualitatively, the same flame dynamics when compared to those from the experiments, and that the fire plumes are sensitive to small variations in the asymmetry of the wind shears, including the appearance of swirling flames within the fire plumes.