• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.1-8
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• 2009

Accumulated slag mass was predicted to estimate accurate performance of kick motor (KM) system. The validation of numerical analysis was performed with mass flow rate measured at the 4th ground test of the KM. The study described here includes the internal flow field of KM at various time steps during burning. Slag mass accumulation was analyzed through the aluminum oxide particle paths to predict slag mass deposition. Numerical analysis to solve both flow field and droplet accumulation was performed with Fluent 6.3 program. Analysing the effects of the acceleration, starting position and diameters of the aluminum oxide particles, total slag mass accumulation was obtained.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.223-227
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• 2003

The method of flame hole dynamics is demonstrated as a mean to simulate turbulent flame extinction. The core of the flame hole dynamics involves derivation of a random walk mapping for the flame holes, created by local quenching, between the burning and quenched states provided that the dynamic characteristics of flame edges is known. Then, the random walk mapping is projected to a background turbulent field. The numerical simulations are carried out with the further simplifications of flame string and unconditioned scalar dissipation rate. The simulation results show how the chance of partial quenching is influenced by the crossover scalar dissipation rate. Finally, a list of improvements, necessary to achieve more realistic turbulent flame quenching simulation, are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.281-288
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• 2004

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by improving the burning rate and by increasing the flame temperature. Flame figures, OH radical intensities, temperature distributions and emissions concentration were examined according to oxygen enriched concentration(OEC) in a turbulent diffusion flat flame. As long as the oxygen enriched concentration was increased, the length and volume of the flat flame was decreased while OH radical intensity was raised and the flame temperature was increased. However, RMS of the fluctuating temperature was decreased, and more homogeneous temperature field was formed. Thermal NO also was increased with increase of oxygen enriched concentration, but CO was decreased due to the increase of chemical reaction rate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1060-1065
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• 2007

This paper summarizes a design procedure of radiated noise from engine blocks of marine engines. This air-borne noise is one of the significant noise contributors including the aeroacoustic noise due to intake and exhaust and the re-radiation due to structure-borne noise. Excitation forces by engine operations are evaluated taking into account the power generation mechanism from the burning process to the subsequence motion of internal parts; piston, connecting rod, and crank shaft. The acoustic transfer vector method is incorporated to effectively simulate the radiated noise field under the various operation conditions. A contribution analysis for the various excitations to the radiated noise is conducted. It is found that the firing pressure is the main source of the radiated noise, and so the structure of the cylinder can be modified to significantly reduce the radiated noise from the engine block.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1775-1783
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• 2003

The method of flame hole dynamics is demonstrated as a mean to simulate turbulent flame extinction. The core of the flame hole dynamics involves derivation of a random walk mapping for the flame holes, created by local quenching, between burning and quenched states provided that the dynamic characteristics of flame edges is known. Then, the random walk mapping is projected to a background turbulent field. The numerical simulations are carried out with further simplifications of flame string and unconditioned scalar dissipation rate. The simulation results show how the chance of partial quenching is influenced by the crossover scalar dissipation rate. Finally, a list of improvements, necessary to achieve more realistic turbulent flame quenching simulation, are discussed.

• Journal of the Korean Society of Combustion
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• v.8 no.1
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• pp.36-45
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• 2003

The subject of turbulent premixed flames has been focused by many researchers for a number of decades. Especially, Borghi suggested a magnificent diagram classifying turbulent combustion areas and Lipatnikov and Chomiak modified this diagram. Recently, experimental techniques have been developed so that we can use PIV for measuring 2D velocity field and apply OH PLIF techniques for obtaining flame locations. In present study, a new diagram is proposed using strain rates and OH signal intensity. Thus, simultaneous PIV and OH PLIF measurements are used for shear strain rates and flame locations, respectively. It is believed that the shear strain rates represent flow characteristics such as turbulence intensity and the OH intensity indicates the flame characteristics such as burning velocities.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.132-137
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• 2005

The burning characteristics of interacting spherical droplet in a turbulent flow are numerically investigated. The transient combustion of 3-dimensionally arranged droplets, both the fixed streamwise droplet distances of 3 radii and 10 radii and different turbulence intensities, is studied. The results obtained from the present numerical analysis show that droplet vaporization rate for heptane droplet is insensitive to turbulence intensity, and that the transient flame configuration and retardation of droplet surface temperature augmentation with streamwise droplet spacing substantially influence vaporization process of interacting droplets. Single flame mode in which individual flames are merged into single flame, with decreasing streamwise droplet spacing, becomes faster. Therefore, vaporization rate of the second droplet with decreasing streamwise droplet spacing decreases remarkably with flame movement.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.261-267
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• 2003

The present study investigates the fire suppression characteristics using a water mist fire suppression system. Numerical simulations of fire suppression with water mist are performed with considering the interaction of fire plume and water droplet, droplet evaporation, and combustion of pool fire. The predicted temperature fields of smoke layer are compared with that of measured data. Numerical results agree with the experimental results within 5$^{\circ}C$ in the case without water mist In the case of fire suppression with water mist, numerical results dose not predict well lot temperature field in the gradual cooling region after water mist injection. But the predicted results of initial fire suppression are in good agreement with that of measured data. The reason of the discrepancy between predicted and measured data is due to the variation of turning rate during the injection of water mist. The effect of burning rate on the fire suppression is left as future study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2385-2394
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• 1992

Granular solid propellants having energy and fast burning rate produce great thrusts within extremely short time intervals. Thus numerical researchs prevailed rather than experimental. Using a 2-phase fluid dynamics model among 1-dimensional 2-phase models, a numerical program was set up to describe reacting flow fields, moving boundary with oscillating pressure waves and constitutive laws research. It deserves special emphasis that correlations of convective heat transfer coefficient and viscous drag force among constitutive laws are tested and discussed because slight variations of their constants make a large influence on their results. In this calculations, some of correlations make the large difference in results. Therefore constitutive laws for convective heat transfer coefficient and viscous drag force need more considerations with experiments.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.2
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• pp.125-131
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• 1993

Electrostatic Precipitator has been widely used to get high efficiency which is required for collection of fine particles. In order to provide collection efficiency and size distribution data for a pilot electrostatic precipitator, a pilot study has been conducted on fly ash from pulverized coal burning apparatus. The aims of this study are to investigate characteristics of electric charge, to measure collection efficiency varied with the applied voltage, to get an optimum current and current density. Optimum current density was obtained to 0.7mA/$cm^2$ at the average electric field strength 2.33kV/cm in this experiment. Maximum particle collection efficiency was indicated 99.21% at the applied voltage 7kV. Finally, particle size distribution is also compared with photographic results. Both coarse and fine particles at the range of 0.5$\sim$2$\mu$m and 3$\sim$10 SEM $\mu$m were clearly removed by increasing applied voltage.