• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.15-21
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• 2011

An experimental study was conducted to investigate the flame stability of the synthetic gas (syngas) using an impinging premixed jet burner. Since the syngas mainly consisted of $H_2$ and CO, the $H_2$/CO mixture was simulated as the syngas. $H_2$/CO mixture ratios, fuel/air mixture velocities and equivalence ratios were used as major parameters on the flame stabilitym The role of the impinging plate on the flame stability was also examined. In addition, laminar burning velocities of the $H_2$/CO mixture were predicted numerically to understand the characteristics of the flame stability for the syngas. The increase in the H2 concentration into the syngas brings about the extension of the blowout limit and the reduction in the flashback limit in terms of the stable flame region. The impinging jet plate broadened the blowout limit but does not play important role in changing of the flashback limit. Finally, it was found that the stability region of the flame using the syngas, which is expressed in terms of the mixture velocity and the equivalence ratio in this study, significantly differed from that of $CH_4$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1087-1096
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• 2001

The dynamic structures of unsteady CH$_4$/Air jet diffusion flame with a flame-vortex interaction were numerically investigated. A timed-dependent, axisymmetric computational model and a low mach number approximation were employed in the present calculation. A two-step global reaction mechanism which considers 6 species, was used to calculate the reaction rates. The predicted results including the gravitational effect show that the large outer vortices and the small inner vortices can be well simulated without any additional disturbances near nozzle tip. It was found that the temperature and species concentrations have deviated values even for the same mixture fraction in the flame-vortex interaction region. It was also shown that the flame surface is not deformed by the inner vortex in upstream region, while in downstream region, the flame surface is compressed or stretched by the outer vortex roll-up. The present unsteady jet flame configuration accompanying a flame-vortex interaction is expected to give good implications for the unsteady structures of turbulent flames.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.395-405
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• 2020

Compartment fire tests were performed using kerosene and Jet A-1 as fire sources to evaluate the relationship between flame temperature and opening size. The tests were performed for a fire caused by the release of kerosene owing to vehicle impact, and for a fire caused by the release of Jet-A-1 owing to airplane collision. The compartment fire tests were performed using a 1/3-scale model of a metal storage cask when the flame temperature was deemed to be the highest. We found the combustion time of Jet-A-1 to be shorter than that of kerosene, and consequently, the flame temperature of Jet-A-1 was measured to be higher than that of kerosene. When the opening was installed on the compartment roof, even though the area of the opening was small, the ventilation factor was large, resulting in a high flame temperature and long combustion. Therefore, the position of the opening is a crucial factor that affects the flame temperature. When the metal storage cask was stored in the compartment, the flame temperature decreased proportionally with the energy that the metal storage cask received from the flame.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.401-404
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• 2006

An axisymmetric simulation with detailed chemistry and fine resolution mesh is conducted for the $LOX/GH_2$ jet flame in rocket engine combustor. A preliminary result is shown for a single shear coaxial injector element. The fundamental features of the $LOX/GH_2$ coaxial jet flame is explored by the analysis of simulated flame.

• Fire Science and Engineering
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• v.23 no.1
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• pp.55-62
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• 2009

A general combustion characteristics of forcing nonpremixed jet in laminar flow rates have been conducted experimentally to investigate the effect of forcing amplitude with the resonant frequency of fuel tube. There are two patterns of the flame lift-off feature according to the velocity increasing; one has the decreasing values of forcing amplitude on the lift-off occurrence when a fuel exit velocity is increasing, while the other has the increasing values. These mean that there are the different mechanisms in the lift-off stability of forced jet diffusion flame. Especially, the characteristics of attached jet flame regime are concentrically observed with flame lengths, shapes, flow response and velocity profiles at the nozzle exit as the central figure. The notable observations are that the flame enlogation, in-homing flame and the occurrence of a vortical motion turnabout have happened according to the increase of forcing amplitude. It is understood by the velocity measurements and visualization methods that these phenomena have been relevance to an entrainment of surrounding oxygen into the fuel nozzle as the negative part of the fluctuating velocity has begun at the inner part of the fuel nozzle.

• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.14-20
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• 2009

Direct numerical simulations(DNS) were performed for the prediction of transient buoyant jet diffusion flames where the Froude numbers(Fr) are 5 and 160, respectively. The thermodynamic and transport properties were evaluated using CHEMKIN package to enhance the prediction performance of the DNS code. The simulated buoyant jet diffusion flame of Fr=5 and 160 showed the transient, dynamic motion well. It was identified that the buoyant jet flames were flickered periodically, and the simulated flickering frequency of the jet diffusion flame of Fr=5 was 12.5Hz, which was in good agreement with the experimental results. The flamelet structures of the buoyant jet diffusion flames could be well understood by comparing the scalar dissipation rates(SDR) and the heat release rates(HRR) of the flames. It was found that the SDR was strongly coupled with the HRR in the buoyant jet diffusion flames.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.259-266
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• 2009

An experimental study was conducted to investigate the effects of forcing amplitude on the flow structure near the nozzle exit of forced jet diffusion flames. The jet was excited up to the blowout occurrence by a considerable large amplitude with a periodic velocity fluctuation at the tube resonating frequency. In the attached flame regime, we disclosed the very interesting result newly that adding of a moderate forcing amplitude caused the jet flame to become longer in spite of being forced. Particular attention is focused on the turnabout mechanism of vortex roll-up around the elongated flame, which has not been reported previously, and on the inner coherent structure of the forced jet in the attached flame regime. From the velocity and flow visualization results, it was ascertained that the surrounding air due to the occurrence of negative velocity parts was suck into the fuel nozzle. To aid in understanding the rotating phenomenon of coherent structure, we present a schematic diagram of the turnabout mechanism of vortex roll-up. The mechanism of vortex turnabout phenomenon can be easily understood by considering the positive and negative velocity amplitudes about the instantaneous velocity of the forcing flow, as shown in this diagram.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.193-204
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• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymmetric 2-D CH$_{4}$ jet diffusion flame. Calculations were carried out twice with the $C_{2}$-Thermal Mechanism including $C_{2}$ and thermal NO reactions and the $C_{2}$-Full Mechanism including prompt NO reactions in addition to the above $C_{2}$-Thermal NO mechanism. The results show that the flame structures such as flame temperature, major and minor species concentration are indifferent to respective mechanisms. The production path of Thermal NO is dominant comparing with that of Prompt NO in total NO production of pure CH$_{4}$ jet diffusion flame. This is because thermal NO mechanism mainly contributes to positive formation of NO in the whole flame region, but Prompt NO mechanism contributes to negative formation in the fuel rich region. In addition, 0$_{2}$ penetration near the nozzle outlet affects the flame structures, especially N0$_{2}$ formation characteristics.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.4
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• pp.410-416
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• 1983

This study presents the combustion characteristics and flame structure of annular swirling flow when there were changes the equivalence ratio and swirl number of swirling jet of fuelair mixture. The conclusions of this study are as follows; During the investigations in which the change of equivalence ratio and swirl number were studied, three basic shapes of flame were observed in this study. Visible flame lengths of swirling jet results in the decrease with increasing of swirl number and air-fuel ratio of mixture. Radial distribution of flame temperature with strong swirl is higher than that of weak swirl at the same equivalence ratio of mixture. The angle of spread of the annular jet increases with the increase of swirl number. When the swirl intensity is increased in a jet, the decay of concentration of carbon dioxide is decreased with the distance from nozzle exit of burner.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.1-10
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• 2018

An experimental study was performed for the behavior of the burner flame which results from burning of the liquid hydrocarbon fuel atomized by an ultrasonic transducer. Configurations of the flame and combustion-field were caught by both high-speed camera and thermo-graphic camera, and those images were analyzed in detail through a image post-processing. As a result, the combustion-field grew and reaction-temperature rose due to the strengthening of combustion reaction with the increasing flow-rate of carrier-gas. In addition, a phenomenon of flame flickering was discussed through the comparative analysis of the variational behavior between the visible flame and IR (Infrared) flame-field. Also, the flickering frequency of the flame was confirmed through FFT (Fast Fourier Transform) analysis employing the flame area.