• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.578-588
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• 1992

In order to predict the effect of swirl on the structure of concentric laminar jet diffusion flame, present study examined the effect of swirl on the flame characteristics by numerical numerical analysis through theoretical model. The theoretical model has been developed for the co-axial laminar jet flame such that the fuel and air are supplying with swirl through inner and outer co-axial tube respectively. For the parametric study, swirl number, Reynolds number of fuel and air and directions of swirl are chosen as important parametes. The results of study show that the flame with width and shorter length is formed by larger swirl number. The important factor of the flame shape is the recirculating zone formed around jet axis near the exit of nozzle. In case of weak swirl, the effect of directions of swirl is not appeared. However, for the strong swirl, the flame with shorter length are appeared in case of counter-swirl compared with the case of co-swirl.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.63-71
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• 2003

This paper presents a robust slewing control of a flexible space structure based on sliding surface design. A sliding surface is designed for a single-axis rest-to-rest slewing in view of target angle, target angular velocity, and root monent of the flexible appendage. In comparison with the Lypunov control law, both controllers guarantee the stability and command tracking capabilities for nominal system. It is also shown that the designed control law provides further robustness to internal/external uncertainties. Extending the results of a single-axis maneuver, a sliding mode control law was sought for an arbitrary three-axis maneuver. Quaternion was used to determine the attitude of a space structure and sliding surfaces were designed for each axis, thereby a robust control law was derived considering the coupling effects between each rotational axis during the maneuver. Several numerical examples were demonstrated to show the effectiveness of the designed control law.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.12-23
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• 2021

In this study, the combustion instability characteristics of low-swirl injector and high-swirl injector is compared by model gas turbine combustor. To compare of unstable behavior in high-swirl injector and low-swirl injector, we performed lots of measurement of combustion instability, with variable of equivalence ratio, combustor length and injector type. The results shown that longitudinal instability occur dominantly in model gas turbine combustor. In addition, it was found that high-swirl injector has more wide range of unstable regime than low-swirl injector. The blockage ratio what one of a parameter in low-swirl injector has not much effected in aspects of overall combustor behavior. Also, revealed that combustion instability occurred in the same combustor length has same properties, regardless of the injector type.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.79-88
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• 2006

In the present paper, the swirl flow structure and flame characteristics of turbulent premixed combustion 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. When inlet swirl number is increased, the distinct flow structures, such as the shapes of corner recirculation and center toroidal recirculation zone, are observed and the flame length is shorted gradually. Also, the phenomena of flashback are identified at strong swirl intensity. In order to get the accurate description of unsteady flame behavior, the predictive ability of the acoustic wave in a combustor is primarily evaluated. It is found that the vortex generated near the edge of step plays an important role in the flame fluctuation. Finally it is examined systematically that the flame and heat release fluctuation are coupled strongly to the vortex shedding generated by swirl flow and acoustic wave propagation from the analysis of flame-vortex interaction.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.943-948
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• 2000

The Twin-fluid Swirl Nozzles are used in many parts of the industry to produce homogeneous spray. This study is to investigate the effects of outer air swiller and inner water swiller on atomization of liquid.. The experiment was carried out with increasing air-flow rate at constant liquid-flow rate and with changing outer air swiller angle and inner water swiller angle. A Particle Dynamics Analyzer(PDA) was used to measure drop size, mean and ms values of axial velocity, number density and Sauter mean diameter(SMD). The axial mean velocity and SMD of droplets were measured along the center line and radial directions. It was found that the higher air flow-rate resulted in the smaller Sauter mean diameter of liquid spray and the higher axial mean velocity of droplets. This experimental results will be conveniently used for the preliminary design stage of twin-fluid nozzle development.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2002.05a
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• pp.62-65
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• 2002

• Proceedings of the Mineralogical Society of Korea Conference
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• 2002.05a
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• pp.66-69
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• 2002

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.317-318
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• 2015

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.06a
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• pp.89-94
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• 2004

Profile ring rolling process for large slewing rings of alley steels are developed. A profile ring with a round groove located asymmetrically on the outer surface is rolled. The process is simulated by the finite element method. The general-purpose commercial finite element analysis software, MSC.Superform, was used. Experiments are carried in the ring rolling machine and compared with the analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.485-492
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• 2013

The effect on collection efficiency with 2-stage vortex finder diameter and back mixing of solid flow due to swirling intensity, turbulence eddies, wall bouncing using the residence time distribution of particle flow in a common and modified cyclone. Higher collection efficiencies of fly ash in a modified cyclone(S = 13, 15cm) are showed than common cyclone. Collection efficiency in modified cyclone was highest at 2-stage vortex finder diameter, S = 13 cm. Variances of residence time distribution and average residence times of glass bead were increased with a diameter(S) of 2-stage vortex finder due to swirling intensity and turbulence eddies. Back mixing of solid flow in a modified cyclone were increased with a gas inlet velocity and showed higher than a common cyclone.