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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers B
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
Editor in Chief :
Volume & Issues
Volume 25, Issue 12 - Dec 2001
Volume 25, Issue 11 - Nov 2001
Volume 25, Issue 10 - Oct 2001
Volume 25, Issue 9 - Sep 2001
Volume 25, Issue 8 - Aug 2001
Volume 25, Issue 7 - Jul 2001
Volume 25, Issue 6 - Jun 2001
Volume 25, Issue 5 - May 2001
Volume 25, Issue 4 - Apr 2001
Volume 25, Issue 3 - Mar 2001
Volume 25, Issue 2 - Feb 2001
Volume 25, Issue 1 - Jan 2001
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Flow Induced by the Uniform Motion of Top Plate over the Bottom Plate with Vertical Fin
Park, Jun-Sang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 877~884
DOI : 10.22634/KSME-B.2001.25.7.877
A theoretical analysis is conducted on the Stokes flow in a narrow channel. A vertical fin is mounted on the bottom plate and the flow is induced by uniformly sliding top plate. The governing harmonic equation was solved in the transformed ζ-plane, which is obtained by applying conformal mappings to the physical plane. By using well-known transformation technique, closed-form expressions for velocity and skin frictional stress on the top and bottom plates were obtained.
Large Eddy Simulation of Turbulent Flow Inside a Sudden Expansion Cylinder Chamber
Seong, Hyeong-Jin ; Go, Sang-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 885~894
DOI : 10.22634/KSME-B.2001.25.7.885
A large eddy simulation(LES) is performed for turbulent flow in a combustion device. The combustion device is simplified as a cylinder with sudden expansion. To promote turbulent mixing and to accommodate flame stability, a flame holder is attached inside the combustion chamber. Emphasis is placed on the flow details with different geometries of the flame holder. The subgrid scale models are applied and validated. The simulation code is constructed by using a general coordinate system based on the physical contravariant velocity components. The calculated Reynolds numbers are 5000 and 50000 based on the bulk velocity and the diameter of inlet pipe. The predicted turbulent statistics are evaluated by comparing with the LDV measurement data. The agreement of LES with the experimental data is shown to be satisfactory.
Numerical Calculations on Flow and Behavior of Pulverized Coal and Ash Particles in 2-Stage Entrained-Flow Gasifier
Hwang, Jung-Ho ; Park, Sun-Ho ; Jung, Jin-Do ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 895~904
DOI : 10.22634/KSME-B.2001.25.7.895
Flow fields, temperature distributions, and particle trajectories in a 2-stage entrained-flow gasifier are calculated using a CFD code, FLUENT. Realizable k-
model is used as a turbulent model. Because of swirling flow there appear recirculation regions near the burners. The characteristics of flow fields and temperature distributions in the gasifier are dependent on the swirl number of the system. Mean residence time of the particles in the reductor is inversely proportional to particle size, particle density and swirl number. As the swirl number is increasing, the particles injected from the combustor burners approach the wall near the combustor burners, which prevents the particles from entering the reductor and thus attatching the reductor wall. If the lower combustor burner angle is larger than the higher combustor burner angle for a given swirl number, the particles may move toward the reductor and cause ash/slag deposition problem.
Large-Scale Turbulent Vortical Structure Inside a Sudden Expansion Cylinder Chamber
Seong, Hyeong-Jin ; Go, Sang-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 905~914
DOI : 10.22634/KSME-B.2001.25.7.905
A large eddy simulation(LES) is performed for turbulent flow around a bluff body inside a sudden expansion cylinder chamber, a configuration which resembles a premixed gas turbine combustor. To promote turbulent mixing and to accommodate flame stability, a flame holder is installed inside the combustion chamber. The Smagorinsky model is employed and the calculated Reynolds number is 5,000 based on the bulk velocity and the diameter of the inlet pipe. The simulation code is constructed by using a general coordinate system based on the physical contravariant velocity components. The predicted turbulent statistics are evaluated by comparing them with the laser-doppler velocimetry (LDV) measurement data. The agreement of LES with the experimental data is shown to be satisfactory. Emphasis is placed on the time-dependent evolutions of turbulent vortical structure behind the flame holder. The numerical flow visualizations depict the behavior of large-scale vortices. The turbulent mixing process behind the flame holder is analyzed by visualizing the sectional views of vortical structure.
PIV Measurement of Circular Cylinder Wake Using Vortex Tracking Phase-Average Technique
Kim, Gyeong-Cheon ; Yun, Sang-Yeol ; Kim, Sang-Gi ; Bu, Jeong-Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 915~922
DOI : 10.22634/KSME-B.2001.25.7.915
A new phase-average technique using instantaneous velocity fields obtained by a PIV method has been developed. The technique tracks vorticity centers and estimates the value of circulation for a chosen domain. The locations of vortex-centers and the magnitudes of circulation are matched together then showing a sine wave feature due to the periodic vortex shedding from the circular cylinder. Ensemble averaged and phase averaged velocity fields are successfully measured for the circular cylinder wake where Reynolds number is 3900 based on free stream velocity and cylinder diameter. The convection velocities of the vortices center and the vortex shedding frequency were measured by a single hot-wire probe.
Generation of uniform Fine Droplets Under Spindle Mode in Electrohydrodynamic Atomization
Lee, Sang-Yong ; Kim, Myeong-Chan ; Kim, Sang-Su ; Kim, Yu-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 923~932
DOI : 10.22634/KSME-B.2001.25.7.923
A series of experiments were conducted to generate fine liquid(water) drops through the electrohydrodynamic atomization process. The atomization mode depended on flow rate and DC voltage input. For water, having electric conductivity larger than 10(sup)-7S/m, the spindle mode turned out to be the only mode to generate uniform-size drops within the range of 30-450 microns that have wide applications. Within this mode, both the uniformity and the fineness of drops were improved at an optimum voltage input for a given flow rate. This optimum voltage increased with increasing of the liquid flow rate. Another important parameter considered was the nozzle material with different electric conductivity and liquid wettability. A stainless-steel nozzle (the material with high electric conductivity and high liquid wettability) and a silica nozzle (the electrically non-conducting material with low liquid wettability) were tested and compared; and more uniform drops could be obtained with the silica nozzle.
Effects of Various Injection Hole Shapes and Injection Angles on the Characteristics of Turbine Blade Leading Edge Film Cooling
Kim, Yun-Je ; Gwon, Dong-Gu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 933~943
DOI : 10.22634/KSME-B.2001.25.7.933
Using a semi-circled blunt body model, the geometrical effects of injection hole on the turbine blade leading edge film cooling are investigated. The film cooling characteristics of two shaped holes (laterally- and streamwise-diffused holes) and three cylindrical holes with different lateral injection angles, 30°, 45°, 60°, respectively, are compared with those of cylindrical hole with no lateral injection angle experimentally and numerically. Kidney vortices, which decrease the adiabatic film cooling effectiveness, appear on downstream of the cylindrical hole with no lateral injection angle. At downstream of the two shaped holes have better film cooling characteristics than the cylindrical one. Instead of kidney vortices, single vortex appears on downstream of injection holes with lateral injection angle. The adiabatic film cooling effectiveness is symmetrically distributed along the lateral direction downstream of the cylindrical hole with no lateral injection angle. But, at downstream of the cylindrical holes with lateral injection angle, the distribution of adiabatic film cooling effectiveness in the lateral direction shows asymmetric nature and high adiabatic film cooling effectiveness regions are more widely distributed than those of the cylindrical hole with no lateral injection angle. As the blowing ratio increases, also, the effects of hole shapes and injection angles increase.
Numerical Study of Shear-Enhanced Turbulent Diffusion
Lee, Chang-Hun ; Choe, Jae-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 944~951
DOI : 10.22634/KSME-B.2001.25.7.944
The purpose of this study is to investigate the effect of shear on turbulent diffusion. Turbulent Couette flows at low Reynolds number are numerically simulated using a Lagrangian PDF method. Flow field and particle trajectories are computed and analyzed in detail. Statistics for particle dispersion obtained from numerical simulations is compared with the classical scaling relations for dispersion in a shear flow.
Phenomena of Hyperbolic Heat Conduction in the Hot Mold with an Inner Defect
Lee, Gwan-Su ; Im, Gwang-Ok ; Jo, Hyeong-Cheol ; Kim, U-Seung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 952~957
DOI : 10.22634/KSME-B.2001.25.7.952
In the glass forming process, the phenomena of hyperbolic heat conduction in the hot mold with an inner defect are studied analytically. It is shown that the temperature predicted by the parabolic model is underestimated compared to the one by the hyperbolic model. As the rmal wave is reflected from the area with defects and then arrives at the surface supplied by the heat flux, it is expected that there exists thermal shock in the materials. The area with defects is assumed to be adiabatic since its thermal conductivity is much lower compared to the one of the material. The results also indicate that the sudden temperature -jump in the mold surface can cause diverse problems such as glass defect (embryo mark, etc), oxidation of mold and coating, and change of material properties.
Effect of Convection on the Solidification Microstructure of Hyper-Peritectic Systems
Park, Byeong-Gyu ; Kim, Mu-Geun ; Park, Jang-Sik ; Kim, Geun-O ; Choe, Jae-Gwang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 958~966
DOI : 10.22634/KSME-B.2001.25.7.958
This study has examined the microstructural development in the Bridgman type directional solidification of hyper-peritectic Sn-Cd alloys, and the temperature and flow field have been numerically simulated to see if there is any change induced by convection. The directional solidification experiments carried out in quartz tubes with inside diameters of 0.4∼6mm showed that the resulting microstructures are clearly dependent on the size of tube diameters. The bigger ampoules where the effect of convection is highly expected produced saw-like structures resulting from the primary
phase growing together at a planar solid-liquid front, with the former being surrounded by the latter. In the smaller ampoules, where the effect of convection is expected low however, the saw structure disappears, and as is understood from the theoretical prediction based on diffusion-controlled solidification the initial growth of the primary
phase is replaced by the nucleation of the peritectic
phase whose growth continues to the end of the solidification.
An Experimental Study on a Flowfield Characteristics in a Throttle Valve of SI Engine
Kim, Cheol ; Kim, Seong-Cho ; Choe, Jong-Geun ; Lee, Seok-Jeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 967~974
DOI : 10.22634/KSME-B.2001.25.7.967
Experimental investigations on the flow characteristics of downstream region of a butterfly valve, which is used in SI engine, have been conducted according to Reynolds number and valve angle. Measurement programs of the flowfield using x-type of hotwire anemometry include the mean and fluctuating velocity, turbulnet intensity, shear stress, power spectrum and pressure loss coefficient. Experimental results show that flow characteristics and independent of relatively high Reynolds number; 60,000 and 80,000. It is also seen that streamwise mean velocities have relatively large velocity gradient around the butterfly valve with increasing the valve opening angle and this trend appears even in the far downstream region. The distributions of turbulent intensity and shear stress show irregular behavior regardless of the valve opening angle and those of the case of the valve opening angle of 45°are the largest. The pressure loss coefficient of the body surface of the throttle valve increases mildly with the increase of Reynolds number and increases rapidly with the reduction of the valve opening angle.
Thermal Analysis of Hot Roller in a Dry Film Laminator
Im, Gwang-Ok ; Lee, Gwan-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 975~980
DOI : 10.22634/KSME-B.2001.25.7.975
The thermal analysis of the hot roller in a dry film laminator is studied numerically by steady-state two-dimensional heat transfer. In the laminating process for PDP glass or PCB, the temperature distributions in a hot roller are presented considering the effects of the roller rotation speed and the inner and outer radii of the roller. The results show that the temperature distributions are strongly dependent on Peclet number. If Pe number becomes larger, the iso-thermal lines are more concentric about the rotating axis and the temperature difference on the hot roller surface decreases exponentially. It also shows that if the contact angle between the roller and the film becomes smaller the temperature difference becomes smaller. However, the changes of the rollers inner or outer radius have little effect on the temperature difference.
Evaporation Heat Transfer and Pressure Drop of R-22 and R-410A in Small Sized Micro-Fin Tubes
Kim, Yong-Chan ; Hwang, Jun-Hyeon ; Yun, Rin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 981~988
DOI : 10.22634/KSME-B.2001.25.7.981
Characteristics of evaporation heat transfer in 6.2 and 5.1mm OD micro-fin tubes were investigated in the present study. The data were taken at evaporation temperatures of -5
and heat fluxes 5kW/
. Mass flux was consequently maintained at 210, 300 and 410kg/
s for the 6.2mm OD tube and 465, 500 and 600kg/
s for the 5.1mm OD tube. The effects of heat flux, mass flux, and outer diameter on the heat transfer coefficient are explored in the present study. The data showed that the evaporation heat transfer coefficient for the 6.2mm OD tube was averagly higher by 16% than that for a 7.0mm OD tube, while the 5.1mm OD tube had approximately 30% higher value than the 6.2mm OD tube.
A Study on Flowfield-Dependent Mixed Explicit-Implicit Method in Heat and Fluid Dynamics Problems
Mun, Su-Yeon ; Song, Chang-Hyeon ; Lee, Chung-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 989~996
DOI : 10.22634/KSME-B.2001.25.7.989
High-speed and low-speed flows are simulated numerically by flowfield-dependent mixed explicit-implicit (FDMEI) method. This algorithm depends on implicitness parameters of convection, diffusion, diffusion gradients, and source terms which are calculated from the changes of local Mach, Reynolds, Peclet, and Damkohler numbers between adjacent nodes. Convection phenomena or shock waves are resolved from Mach number-dependent implicitness parameters whereas diffusion or viscous actions are simulated by Reynolds number or Peclet number-dependent implicitness parameters. Fluctuation components of all variables are properly accommodated spatially and temporally in the FDMEI procedure. To illustrate, some benchmark example problems are presented for comparisons of the FDMEI results with other available data. These results appear to be encouraging and point toward the need for further investigations of the FDMEI theory.
The Effect of Swirl Number on the Flow Characteristics of Flat Flame Burner
Jang, Yeong-Jun ; Jeong, Yong-Gi ; Jeon, Chung-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 7, 2001, Pages 997~1004
DOI : 10.22634/KSME-B.2001.25.7.997
Burner of Flat Flame type expects the uniform flame distribution and NOx reduction. The characteristics of Flat Flame Burner become different according to swirl number in the burner throat. Experiments were focused on swirl effect by four types of swirler with different swirl numbers (0, 0.26, 0.6 and 1.24). It shows many different flow patterns according to swirl number using PIV(Particle Image Velocimetry) method. The flow of burner with swirler is recirculated by pressure difference between its center and outside. Recirculated air makes stable in flame, and reduced pollutant gas. In case of swirl number 0, main flow passes through axial direction. As swirl number increased, The backward flow develops in the center part of burner and Flow gas recirculates. This is caused by radial flow momentum becomes larger than axial flow by swirled air and the pressure at center drops against surrounding. As swirl number increases, the radial and axial velocity was confirmed to be larger than low swirl numbers. And turbulence intensity have similar pattern. The CTRZ(Central Toroidal Recirculation Zone) is shown evidently when y/D=1 and S=1.24. The boundary-layer between main flow and recirculated flow is shown that the width is seen to be decreased as swirl number increased.