• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.65-74
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• 2003

Air pollution included Nitric Oxide(NOx) from heating boilers is increased by pursuing better life. Development of low NOx emission boiler is strongly needed. However commercial burner for heating boiler is also asked to be thermal efficient and low-cost manufactuable in addition to low NOx emission. Small space for combustor including burner is usually allowed. In this study, parametric study of compact low NOx burner for heating boiler was done using numerical analysis and experiments. Commerical computational fluid dynamic(CFD) program named CFX 5-6 was used for numerical analysis of low NOx burner using turbulent diffusion flame. Comparison of outlet NO and outlet temperature under various equivalence ratio and fuel flow rate was performed between experiment and numerical analysis.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.29-34
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• 2017

The multi-environment probability density function model has been applied to simulate a turbulent premixed flame in a swirl combustor. To realistically account for the unsteady flow motion inside the combustor, the formulations are derived for the large eddy simulation. The Flamelet generated manifolds is utilized to simplify a multi-dimensional composition space with reasonable accuracy. The sub grid scale mixing is modeled by the interaction by exchange with the mean mixing model. To validate the present approach, the simulation results are compared with experimental data in terms of mean velocity, temperature, and species mass fractions.

• Journal of the Korean Society of Combustion
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• v.22 no.4
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• pp.43-50
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• 2017

In this study, the multi-environment probability density function(MEPDF) approach has been applied to numerically investigate Delft-Jet-in-Hot-Coflow(DJHC) turbulent flames under Moderate or Intense Low-oxygen Dilution (MILD) combustion condition. Computations are made for two different jet velocities(Re = 4100 and 8800). In terms of mean axial velocity, temperature, and turbulent kinetic energy, numerical results are in reasonably good agreements with experimental data even if there exist the noticeable deviations in downstream region. Based on numerical results, the detailed discussions are made for the essential features of the non-visible flame structure and MILD combustion processes.

• Journal of the Korean Society of Combustion
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• v.5 no.1
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• pp.67-79
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• 2000

An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swril flow(DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microstructure using thermophoretic sampling particle diagnostic(TSPD) as TEM were carried out. The NOx, $CO_2,\;O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.492-501
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• 1994

This study is an analysis of the turbulent diffusion flame with swirl flow and the calculated results are compared with experimental data in case of various swirl numbers and air-fuel rations. The mathematical model is restricted to single-phase, diffusion controlled combustion with swirl flow. Values of local flow properties were obtained by solving appropriate differential equation for continuity, momentum, stagnation enthalpy, concentration, turbulence energy, dissipation rate of turbulence energy, and the mean square of concentration fluctuation. The method is proposed for calculating the local probability of chemical reaction based on the use of the probability density function for the mixture fraction.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.1009-1018
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• 2002

The Representative Interactive Flamelet (RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the direct injection diesel engine. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF concept has the capabilities to predict the auto-ignition and subsequent flame propagation in the diesel engine combustion chamber as well as to effectively account for the detailed mechanisms of soot formation, NOx formation including thermal NO path, prompt and nitrous 70x formation, and reburning process. Special emphasis is given to the turbulent combustion model which properly accounts for vaporization effects on the mixture fraction fluctuations and the pdf model. The results of numerical modeling using the RIF concept are compared with experimental data and with numerical results of the commonly applied procedure which the low-temperature and high-temperature oxidation processes are represented by the Shell ignition model and the eddy dissipation model, respectively. Numerical results indicate that the RIF approach including the vaporization effect on turbulent spray combustion process successfully predicts the ignition delay time and location as well as the pollutant formation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.304-309
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• 2017

This paper studies a nonpremixed turbulent flame in a model scramjet combustor using zonal hybrid RANS/LES method. The numerical domain is divided into two region, RANS and LES region. The interface between the two regions is treated with synthetic eddy method. A model scramjet combustor experimented at German aerospace center is selected for the comparative study. The fuel injection of cracked kerosene surrogate which is composed of ethylene and methane is considered. Turbulent combustion of cracked kerosene surrogate is achieved using flamelet approach.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.38-47
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• 2007

Based upon temperature calibration using the diffusion flame, the temperature and soot concentration of the turbulent flame in a visualized Diesel engine's turbulent flow of flame was qualitatively measured. Two different heads were used to judge the effect of swirl ratio within the combustion chamber. It was possible to measure the highest temperature of the non-swirl head visualized engine which is approximately 2400K, and that the swirl head engine managed up to 2100K. Also, the more the pressure of the spray increases the more the temperature increases due to the improved combustion situation with respect to the visualized diesel engine soot. This experiment also revealed that the KL factor was high where the fuel collided with the walls of the combustion chamber. Moreover the KL factor was high on parts of the chamber where the temperature dropped rapidly.

• Journal of the Korean Society of Combustion
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• v.6 no.2
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• pp.65-70
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• 2001

To investigate statistics of flamelet in a turbulent premixed flame and to obtain components of their burning velocities in a vertical plane above a pipe-flow burner, the local motion of flamelets with respect to gas are measured by specially arranged diagnostics, composed of an electrostatic probe with four identical sensors and a two-color four-beam LDV system. With this technique, the three-dimensional local flame-front-velocity vector is measured by the electrostatic probe for the first time, and simultaneously the axial and radial components of the local gas-velocity vector in a vertical plane above the vertically oriented burner are measured by the LDV system. Two components of burning velocities of planar flamelets can be obtained from these results and are found to be distributed over different directions and to range in magnitude from nearly zero to a few times the planar, unstrained adiabatic laminar burning velocity measured in the unburnt gas. It may be concluded from these results that turbulence exerts measurable influences on flamelets and causes at least some of them to exhibit increased burning velocity.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1084-1093
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• 2010

Large eddy simulation of turbulent premixed flame stabilized by the bluff body is performed by using sub-grid scale combustion model based on the G-equation describing the flame front propagation. The basic idea of LES modeling is to evaluate the filtered-front speed, which should be enhanced in the grid scale by the scale fluctuations. The dynamic subgrid scale models newly introduced into the G-equation are validated by the premixed combustion flow behind the triangle flame holder. The calculated results can predict the velocity and temperature of the combustion flow in good agreement with the experiment data.