• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.1-8
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• 2000

The effects of nozzle arrangements, nozzle distances and fuel flowrates on the flame stabilities such as flame length, liftoff height and blowout characteristics are investigated experimentally. Three nozzle arrangements - diamond 4 nozzle, linear 5 nozzle, cross 5 nozzle- are used. Flame interactions result in the increase of the blowout flowrates and constant turbulent liftoff heights. The flames separated about 10 nozzle diameters are sustained as nozzle attached flames to the higher fuel flowrates than the other separation cases. Normally flames are extinguished at the lifted states. Blowout flowrates are affected by the nozzle configuration, nozzle seperation distance. Blowout flowrates for the diamond- or cross- shaped nozzle arrangements are parabolic function of nozzle distances. Maximum blowout flowrates for the 5 nozzle configuration case except linear one is about 2.9 times that of single equivalent nozzle case. Turbulent liftoff heights are not function of flowrates for the interacting flames.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.190-199
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• 1993

In order to find the effect of flame interaction on NO production, dual laminar diffusion flames issuing from two rectangular nozzles were investigated theoretically. Chemical equilibrium model and Zeldovich mechanism were used in numerical model. The effect of four major parameters on NO production were inspected. These parameters are nozzle spacing, Raynolds number, aspect ratio of nozle cross section and velocity of secondary flow. It is found that interaction of flames enhances production of n. It is also found that multiflames with large spacing, small aspect ratio and strong secondary flow product less n.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.457-462
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• 2011

This paper presents a numerical investigation of deflagration to detonation transition (DDT) induced by shock wave and flame interaction in ethylene-air mixtures. Also shows the change of DDT triggering time by wall cooling effect. A model is consisted of the compressible reactive Navier-Stokes equations. And the effect of viscosity, thermal conduction, molecular diffusion, chemical reaction and wall effect are included. Using this model, the generation of hot spot by repeated shock and flame interaction, occurrence of detonation, and wall cooling effect of detonation confining boundaries are studied.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.3
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• pp.37-48
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• 1989

The effects of burnt gas mixing, which can be caused by turbulent eddy mixing, on the interaction and extinction characteristics of premixed flames are analyzed using large activation energy asymptotics adopting counterflow as a model problem. The results show that the burnt gas mixing, preferential diffusion and heat loss affect the fuel consumption rate, flame temperature and the oxidizer concentration at the flame which influence the flame behavior and the extinction characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.369-374
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• 2010

This paper presents a numerical investigation of the Deflagration to Detonation Transition (DDT) of flame acceleration by a shock wave in combustible gas mixture. A model consisting of the reactive compressible Navier-Stokes equations is used. The effects of viscosity, thermal conduction, species diffusion, and chemical reactions are included. Using this model, the generation of hot spots by repeated shock and flame interaction in front and back of flame and the change of detonation occurrence by various shock intensities (Ms=1.1, 1.2, 1.3) are studied. The simulations show that as the incident shock intensity increases, the Richtmyer-Meshkov (RM) instability becomes stronger and DDT occurrence time is reduced.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.991-1000
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• 1987

Existence of triple flames in a lean-rich concentration field is studied both experimentally and theoretically using large activation energy asymptotic technique adopting counterflow system as a model problem. Experiment shows that in triplet system of a lean and a rich premixed flame separated by a diffusion flame, either lean or rich premixed flame merges with diffusion flame as stretch is increased, such that transition boundary between 3-flame and 2-flame exists. The region in which 3-flame can exist forms an island within rich-lean concentration fields for large stretch, where as it is extends to the line of (.OMEGA.$_{0}$/.OMEGA.$_{F}$)$_{R}$=0 or (.OMEGA.$_{F/}$.OMEGA.$_{0}$)$_{L}$=0 for small stretch. Theoretical results show the qualitative agreement with experiment and the existence of limiting stretch over which 3-flame can not exist.t.t.t.t.t.t.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.96-104
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• 2006

In the present paper, the effects of combustion instability on flow structure and flame dynamic with the configurations of burner exit in a model gas turbine combustor are investigated using large eddy simulation(LES). A G-equation flamelet model is employed to simulate the unsteady flame behavior. As a result of mean flow field, the change of divergent half angle(${\alpha}$) at burner exit results in variations in the size and shape of the central toroidal recirculation(CTRZ) as well as flame length by changing corner recirculation zone(CRZ). The case of ${\alpha}=45^{\circ}$ show smaller size and upstream location of CTRZ than that of $90^{\circ}$ and $30^{\circ}$ by the development of higher swirl velocity. The flame length in the case of ${\alpha}=45^{\circ}$ is the most shortest, while that in the case of ${\alpha}=30^{\circ}$ is the longest by the decrease of effective reactive area with the absence of CRZ. Through the analysis of pressure fluctuation, it is identified that the case of ${\alpha}=45^{\circ}$ shows the most largest damping effect of pressure oscillation in all configurations and brings in the noise reduction of 2.97dB, comparing with that of ${\alpha}=30^{\circ}$ having the largest pressure oscillation. These reasons are discussed in detail through the analysis of unsteady phenomena about recirculation zone and flame surface. Finally the effects of flame-acoustic interaction are evaluated using local Rayleigh parameter.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.41-46
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• 2017

This study has numerically investigated the flame-acoustics interactions in the turbulent partially premixed flame field. In the present approach, in order to analyze the combustion instability, the present approach has employed the LES-based combustion model as well as the Helmholtz solver. Computations are made for the validation case of the partially premixed LIMOUSINE burner. In terms of the FFT data, numerical results are compared with experimental data. Moreover, Helmholtz equation in frequency domain is solved by combining CFD field data including the flight time from a nozzle to the flame zone. Based on numerical results, the detailed discussions are made for the essential features of the combustion instability encountered in the partially premixed burner.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.49-56
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• 2002

A two-dimensional direct numerical simulation is performed to investigate the formation characteristics of a single vortex interacting with $CH_4/N_2$-Air counterflow nonpremixed flame. The numerical method was based on a predictor-corrector scheme for a low Mach number flow. The detailed transport properties and a 16-step augmented reduced mechanism are adopted in this calculation. The budgets of the vorticity transport equation arc examined to reveal the mechanisms leading to the formation, evolution and dissipation of a single vortex interacting with counterflow nonpremixed flame. It is found that the stretching term, which depends on the azimuthal component of vorticity, and radial velocity, mainly generates vortieitv in non-reacting and reacting flows. The viscous and baroclinic torque term destroy the vorticity in non-reacting flow. In addition, the baroclinic torque term due to density and pressure gradient generates vorticity, while viscous and the volumetric expansion terms due to density gradient destroy vorticity in reacting flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.349-355
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• 2005

It has been reported that propane non-premixed interacting flames are not extinguished even in 210m/s if eight small nozzles are arranged along the imaginary circle of 40 ~ 72 times the diameter of single nozzle. In this research, experiments were extended to the methane flame. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric center. The space between nozzles, s, the exit velocity and the role of the jet from the center nozzle were considered. On the contrary to the propane non-premixed flame, small amount of fuel fed through the center nozzle makes the methane diffusion flame stable even at the choking conditions. In the laminar region, the flame at the center nozzle anchored the outer lifted flames.