• Journal of ILASS-Korea
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• v.6 no.3
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• pp.8-16
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• 2001

The present study is focused on modeling the transient behavior of the local flame structure which is especially important for slow reaction processes, such as NOx formation in the radiating flame field. The unsteady flamelet model recently developed has been applied to analyze a steady, turbulent jet flame. Numerical results are compared with experimental data and numerical results of the conventional steady flamelet model. The numerical result reveals that the unsteady flamelet model correctly predicts the nonequilibrium effect upsteam and the subsequent decay of the superequilibrium radical concentrations further downstream.

• Journal of ILASS-Korea
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• v.2 no.1
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• pp.8-17
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• 1997

A study has been carried out on the instability of a conical liquid sheet by using the linear instability theory. Various analytical methods using the Kelvin-Helmholtz instability theory were tried to examine the wave growth on cylindrical liquid sheets. Cylinderical liquid sheets were extended to the case with the conical sheets. Perturbations due to tangential motion as well as longitudinal one were taken into account. And it was assumed the the breakup occurs when amplitude ratio exceeds exp(12), drop sizes were predicted only by theoretical approach. The predicted drop size agreed well with the measured Sauter mean diameter, $D_{32}$.

• Journal of ILASS-Korea
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• v.8 no.1
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• pp.1-8
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• 2003

The flow analysis of the axial fan of rotary burner was performed by SIMPLE(Semi Implicit Method for Pressure Linked Equations) algorithm and finite volume mothod performed in the case of 3-D, incompressible, turbulent flow. In this study, the coordinate transformation was adapted for the complex geometry of axial fan, and the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent flow. Multi-block grid system was used for flow field and divided into four domains such as the inlet, outlet, flow field of rotating vane, and tip clearance. Fan rotation was simulated by rotational motion using MRF(Multiple Rotating Reference Frame) in steady, incompressible state flow.

• Journal of Hydrogen and New Energy
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• v.15 no.1
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• pp.72-81
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• 2004

Study on the analysis of sodium spray fire using Gaussian drop size distribution, which redistributes a droplet spectrum with given mean diameter if its size classes with critical diameter(D>8mm) occur, was carried out. In this case, the oversized droplets were reduced to a stable diameter. Results calculated by the code using Gaussian drop size distribution were in better agreement with AI experimental results than those of NACOM and SPRAY code. The effect of variance on pressure in the test cell appeared greatly by introducing Gaussian function, which could represent various sodium droplet size distribution. The increase of the variance with mean droplet size resulted had an important effect upon the pressure in the test cell.

• Journal of ILASS-Korea
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• v.3 no.3
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• pp.1-13
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• 1998

In this study, an experimental study was performed to investigate the breakup mechanism of vaporizing droplet. A well-controlled experimental apparatus was used to study breakup mechanisms of a monodisperse stream of drops injected into a transverse high temperature and velocity air stream. The experiments gave information$ about the microscopic structure of the liquid drop breakup process, drop breakup regimes, and drop trajectories in high temperature flow region. The breakup time, drop acceleration and wavelength of surface instability wave were measured from a high-magnification and double spark photography. The two instability theories, i.e., Kelvin-Helmholtz instability and Rayleigh-Taylor instability, were estimated by comparing the calculated data with the measurements. The results showed that the breakup time in high temperature flow condition is shortened because the surface tension is decreased by the increase of gas temperature.

• Journal of computational fluids engineering
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• v.12 no.2
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• pp.32-36
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• 2007

NUFLEX is a general purpose program for the analysis 3D thermo/fluid flow and pre/post processor in a complex geometry. NUFLEX is composed of various physical models, such as phase change(solidification/melting) and spray, MHD(Magneto Hydraulic Dynamics) models. It is possible to simulate continuous cast iron process and spray droplet breakup/collision phenomenon. For the verification of these models, compared with the experimental data and commercial CFD code's results. The results show good agreements with experimental and comercial CFD codes's results.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.295-298
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• 2002

In the analysis of the mass distribution and SMD (Sauter Mean Diameter), planar laser imaging technique Is a convenient and useful one when compared to the mechanical patternator or PDPA (Phase Doppler Particle Analyzer). But for the accurate usage of this laser technique, it is required to compensate the signal attenuation and to find the attenuation coefficients. In the present research, we considered effects of the spray distributions on the attenuation coefficient and improved the accuracy of planar laser imaging technique by the reduction of errors issuing from the signal attenuation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.131-134
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• 2007

This numerical analysis was performed in order to validate adoption of the sheet breakup model in high-pressure environment, which were used for prediction of spray characteristics in atmosphere environment. In experiments the higher environment pressure the shorter breakup length; the results of new sheet breakup model predicted the breakup length in good agreement with experimental results qualitatively and quantitatively. Also the shape of spray calculated by numerical analysis were agreed well with experiments quantitatively.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.1-6
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• 2006

The present study is focused on the small scale turbulent mixing processes in the scalar Held. In order to deal with molecular mixing in turbulent flow, the linear eddy model is addressed. In each realization, the molecular mixing term is implemented deterministically, and turbulent stirring is represented by a sequence of instantaneous, statistically independent rearrangement event called by triplet map. The LEM approach is applied with relatively simple conditions. The characteristics of scalar mixing and PDF profiles are addressed in detail.

• Journal of ILASS-Korea
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• v.14 no.1
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• pp.1-7
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• 2009

This study carried out numerical analysis of flow field of combustion gas and sorbent to test sorbent efficiency of DSI process. To provide rapid mixing for increase utilization rate of sorbent, streamwise vorticity can be introduced into the flowing streams by other means; for example, by installing vortex generators immediately downstream of the wavy trailing edge. Computing results show that the degree of sorbent dispersion depends strongly on duct structure. Highest dispersion efficiency received when vortex generator was installed inside of duct. The results presented in this study a optimum condition for the development of practical DSI process.