• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.68-74
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• 2000

Experimental investigation on flame spread along suspended droplet arrays have been conducted with various droplet spacings and ambient air velocities. Especially, an opposed air stream is introduced to simulate fundamental flame spread behaviors in spray combustion. High-speed chemiluminescence imaging technique of OH radicals has been adopted to measure flame spread rates and to observe various flame spread behaviors. The fuel used is n-Decane and the air velocity varies from 0 to 17cm/s. The pattern of flame spread is grouped into two: a continuous mode and an intermittent one. It is found that there exists droplet spcings, above which flame spread does not occur. The increase of ambient air velocity causes the limit droplet spacing of flame spread to become small due to the increase of apparent flame stretch. As the ambient air velocity decreases, flame spread rate increases and then decreases after taking a maximum flame spread rate. This suggests that there exists a moderate air flowing to give a maximum flame spread rate due to enhanced chemical reaction by the increase of oxidizer concentration.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.119-125
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• 1998

In long vertical duct, the aspect of second flame in laminar flame propagating through lycopodium-air mixtures and the behavior of dust particles in neighborhood in front of flame have been examined experimentally. In order to trace the development of second flame to its origin, the velocity and vorticity distribution of dust particles in front of flame were measured by using with the real-time PIV system. The velocity of particles was approximately zero at the central part of flame front and the ahead of the flame leading edge, but maximum near the duct wall. The flame velocity of second flame and the movement of leading flame edge depend mainly on behavior of dust particles by the flow distribution of temperature and pressure.

• Journal of the Korean Society of Combustion
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• v.7 no.2
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• pp.1-6
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• 2002

Characteristics of laminar lifted flames of propane highly-diluted with nitrogen have been investigated at various temperatures of coflow air. At various fuel mole fractions, the base of laminar lifted flames has the structure of tribrachial (or triple) flame. The liftoff heights are correlated well with the stoichiometric laminar burning velocity considering initial temperature at a given coflow velocity. It shows that lifted flames are stabilized on the basis of the balance mechanism between local flow velocity and the propagation speed of tribrachial flame, regardless of the temperature of coflow and fuel mole fraction. Lifted flames exist for a jet velocity even smaller than the stoichiometric laminar burning velocity, and liftoff velocity increases more rapidly than stoichiometric laminar burning velocity as coflow temperature increases. These can be attributed to the buoyancy effect due to the density difference.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.4
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• pp.41-46
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• 1983

The influence of inlet air humidity on the flame velocity and combustion of the spark ignition engine were described experimentally by means of the flame velocity measuring apparatus using ion-current. The flame velocity are greatly influenced air fuel ratio and engine speed, and linealy decrease according to the increasing of inlet air humidity. The flame travell curve is very similar to the rate of mass burned and combustion progressive is estimated mostly by only the rate of mass burned curve. The decreasing of the mean flame velocity is about 0.4m/s for increasing of 0.001 specific humidity and we think the reason is mainly decreasing of thermal conductivity.

• Journal of the Korean Institute of Gas
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• v.13 no.3
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• pp.33-42
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• 2009

A numerical analysis of reactive flow in a liftoff flame is accomplished to elucidate the characteristics of liftoff flame. To verify reliance of numerical calculation, the liftoff heights of liftoff flame for various fuel exit velocities are compared between the existing experimental research results and the present calculation results. The flame propagation velocity is conducted at the flow redirection point which is on a stoichiometric line ahead of flame front. This point was selected constant distance from triple point regardless of fuel exit velocity at the previous research. This causes considerable errors for the flame propagation velocity and scalar dissipation rate. The main issue of the present research is to establish the resonable method to select the redirection point and so that to clarify the relationship between flame propagation velocity and scalar dissipation rate, which is the core properties in a triple flame stability.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.32-37
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• 2012

The aim of this study is to evaluate the characteristics of explosion and flame velocity that can be utilized to factories where Mg-Al alloy metal powders are handled in the form of raw materials, products or by-product for similar dust explosion prevention and mitigation. Because the strength of the blast pressure is the result due to flame propagation, flame velocity in dust explosion can be utilized as a valuable information for damage prediction. An experimental investigation was carried out on the influences of content ratio of Mg-Al alloy (mean particle size distribution of 151 to 161 ${\mu}m$). And a model of flame propagation velocity based on the time to peak pressure and flame arrival time in dust explosion pressure, assuming the constant burning velocity, leads to a representation of flame velocity during dust explosion. As the results, the maximum flame velocity of Mg-Al(60:40 wt%), Mg-Al(50:50 wt%) and Mg-Al(40:60 wt%) was estimated 15.5, 18 and 15.2 m/s respectively, and also tend to change with content ratio of Mg-Al.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.48-53
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• 2009

This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.7-12
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• 2007

To reveal the newly found liftoff height behavior of hydrogen jet, we have experimentally studied the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition. The objectives of the present research are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The velocity of hydrogen was varied from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/s. For the simultaneous measurement of velocity field and reaction zone. PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. As results, it has been found that the stabilization of lifted hydrogen diffusion flames is related with a turbulent intensity, which means that combustion occurs where the local flow velocity is valanced with the turbulent flame propagation velocity.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.705-709
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• 2009

Based on experimental study of lycopodium dust particles' behavior, we suggest the flame propagation model through dust clouds. With dust concentration, flame velocity reaches a maximum value at $170g/m^3$ to exceed the stoichometric concentration for lycopodium-air mixture combustion and decreases slightly in the richer side of $500g/m^3$. At $47{\sim}200g/m^3$, mean velocity of particle increases in proportion to flame velocity. As the sum of burning rate and particle velocity is approximate in flame velocity, the flame propagation velocity with lycopodium dust concentration can be estimated by the calculation and it was found that behavior of particles is useful for better understanding of dust flame propagation velocity.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.737-746
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• 2016

This article describes a comparison on laminar burning velocity measured by Bunsen and spherical flame methods of synthetic natural gas (SNG) with various composition of hydrogen. In this study, the laminar burning velocity measurements were employed by Bunsen burner and cylindrical constant combustor at which flame images were captured by Schlieren system. These results were also compared with numerical based on CHEMKIN package with GRI 3.0, USC-II and UC Sandiego mechanism. In case of spherical flames, the suitable flame radius range and theoretical models were verified using the well-known previous results in methane/air flames. As an experimental condition, hydrogen content of SNG was adjusted 0% to 11%. Equivalence ratios of Bunsen flames were adjusted from 0.8 to 1.6. On the other hand, those of spherical flames were adjusted from 0.6 to 1.4, relatively. From results of this study, the both laminar burning velocities measured in Bunsen and spherical flame methods were resulted in similar tendency. As the hydrogen content increased, the laminar burning velocity also increased collectively. Laminar burning velocity of measured SNG-air flames was best coincided with GRI 3.0 mechanism by comparison of reaction mechanisms.