• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.15-16
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• 2012

The present study aims to investigate quantitatively the hydrodynamic effect on combustion process of pulverized coal particles in large scale combustion chamber using computational analysis, with a general purpose computational fluid dynamics code. Burner hydrodynamics include swirl and turbulence intensity from the burner. To understand the phenomena which are difficult to observe how flow has influence on the combustion process, comparative effect of combustion related coal properties and hydrodynamics is evaluated on flame formation and development in burner flames.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2270-2280
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• 2005

An experimental study is performed for turbulent swirling flow behind a circular cylinder using 2-D PIV technique. The Reynolds number investigated are 10,000, 15,000, 20,000 and 25,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the round cylinder along the test tube. A comparison is included with non swirl flow behind a circular and square cylinder. The recirculation zones are showed asymmetric profiles.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.41-47
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• 2009

An experimental study was performed to confirm the effect of the changing combustor pressure(-30~30 kpa), combustion characteristics were investigated by measuring the local chemiluminescence intensity, the local temperature distribution and emission. In order to investigate combustion ones, the combustor pressure index($P^*$) was controlled in the range of 0.7~1.3 for each equivalence ratio in the present combustion system, where $P^*$ is defined as the ratio of absolute pressure to atmospheric one. The local mean temperature showed the uniform distributions for lower pressure index, which increased with increasing equivalence ratio. The mean $OH^*$ chemiluminescence intensity, showed high level for lower pressure index for ${\Phi}{\get}1.0$ conditions. EINOx decreased with decreasing pressure index for overall equivalence ratio conditions.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.720-726
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• 2001

Two-dimensional, angle-resolved LDV(Laser Doppler Velocimetry) measurements of the turbulent rotating flow field in a confined cylinder have been performed. The configurations of interest are flows between a rotating upper disk with a rod attached by a disk or impeller(${\theta}= 90^{\circ},\;45^{\circ}$) and a stationary lower disk in a confined cylinder. The mean flow velocity as well as the turbulent intensity of the flow field have been measured. The results show that the flow is strongly dependent on the position of the impellers or the disk, negligibly affected by the Reynolds number in turbulent flow. It is observed that the mixing effect of the axial flow impeller(${\theta}= 45^{\circ}$) is better than that of the radial flow impeller(${\theta}= 90^{\circ}$) or a disk.

• Journal of ILASS-Korea
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• v.4 no.4
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• pp.1-8
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• 1999

The concentration and spatial distribution of vapor phases in DI (Direct Injection) gasoline spray were measured quantitatively by exciplex fluorescence method. Fluorobenzene and DEMA (diethylmethylamine) in a solution of hexane were used as the exciplex-forming dopants. The fluorescence intensity of vapor phase were obtained by ICCD camera with the appropriate filter The relationship between fluorescence intensity and vapor concentration was induced fer the purpose of a quantitative analysis. The 2-D vapor/liquid images of fuel spray were captured under the evaporation condition, and the spatial distribution of vapor concentration was obtained. The spatial distribution of liquid phase had hollow-cone shape. And the vapor phase was widely distributed in the whole spray. The behavior of vapor phase was significantly affected by second flow such as entrainment, vortex, while that of liquid phase was scarcely affected.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.417-425
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• 2005

An experimental study is performed on the turbulent swirling flow behind a crcular cylinder using 2-D PIV technique. The Reynolds numbers investigated are 10.000, 15,000. 20.000 and 25.000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the cylinder along the test tube. A comparison is included without swirling flow behind a circular and square cylinder. The recirculation zones are shown unsymmetric profiles.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.138-152
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• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.44-51
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• 2014

Considering the importance of the detailed resolution of the reacting flow field inside a gasifier, the objective of this study lies on to investigate the effect of important variables to influence on the reacting flow and thereby to clarify the physical feature occurring inside the gasifier using a comprehensive gasifier computer program. Thus, in this study the gasification process of a 1.0 ton/day gasifier are numerically modeled using the Fluent code. And parametric investigation has been made in terms of swirl intensity and aspect ratio of the gasifier. Doing this, special attention is given on the detailed change of the reacting flow field inside a gasifier especially with the change of this kind of design and operation parameters. Based on this study, a number of useful conclusions can be drawn in the view of flow pattern inside gasifier together with the consequence of the gasification process caused by the change of the flow pattern. Especially, swirl effect gives rise to a feature of a central delayed recirculation zone, which is different from the typical strong central recirculation appeared near the inlet nozzle. The delayed feature of central recirculation appearance could be explained by the increased axial momentum due to the substantial amount of the presence of the coal slurry occupying over the entire gasifier in gasification process. Further, the changes of flow pattern are explained in detail with the gasifier aspect ratio. In general, the results obtained are physically acceptable in parametric study.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.473-485
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• 1997

Detailed experimental study has been made of air blast kerosene spray flames with and without swirl in combustion air flow. Phase-Doppler detect technique is used to measure Sauter mean diameter, axial component mean and rms velocity, size-velocity correlation, and number density. These measurements are obtained for both nonreacting and reacting cases under several stable flame conditions. The results show that the introduction of swirl to the combustion air modifies the spatial distribution of droplet size, velocity, and number density, and thus alters the flame structure. However, due to the weak swirl intensity, the overall structure of swirling flames are essentially same as that of nonswirling flames. Physical model of structure of air blast atomized spray flames is projected to show that spray flames are composed of three distinct regions: the two-phase mixture region, the main reaction and the intermittent combustion region. Near the atomizer, two phase mixture of droplet and air is formed in the core region. This dense spray region is characterized by high droplet number density and the strong convective effect. There follows the main combustion region where the main flame penetrates within the spray boundary. Main reaction region of these flames are governed by internal group combustion mode. Finally there exists the intermittent combustion region where local group burning or isolated droplet burning occurs.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.141-148
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• 2022

A hybrid turbulence model has developed by combining a sub-grid scale model using dynamic k equation in LES with k-𝜔 SST model of RANS equation. To ascertain potential applicability of the hybrid turbulence model, fully developed turbulent channel flows at Re_𝜏=180 have been simulated of which computational domain has a top wall with coarse cells and a bottom wall with fine cells. The streamwise mean velocity and turbulent intensity profiles showed a good agreement with DNS data when using the hybrid model rather than using a single model in k-𝜔 SST or dynamic k equation models. Computational simulations of turbulent flows around KVLCC2 with a pre-swirl duct have been mainly performed using the hybrid turbulence model. Compared to the results obtained from RANS simulation with k-𝜔 SST model as well as LES with dynamic k equation SGS model, turbulent wakes of the duct in the present simulation using the hybrid turbulence model were very similar to that of LES. Also, the resistances acting on hull, rudder and duct in hybrid turbulence model were similar to those in RANS simulation whereas the viscous forces acting on the hull in LES had a significant error due to coarse cells inappropriate to the sub-grid scale model.