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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
Selecting the target year
Energy Separation Characteristics of Single Hole Vortex Generator
Yu, Gap-Jong ; Jang, Jun-Yeong ; Choe, In-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1005~1012
DOI : 10.22634/KSME-B.2001.25.8.1005
When vortex tubes are applied to enhance the coefficient of performance of refrigeration system, the smaller one is preferable. However, the existing vortex generator with a nozzle hole diameter of 0.5mm was not suitable due to chocking of the nozzle hole. Therefore, experimental investigation was made to find an appropriate geometry of vortex generator, which could give a comparable effect of energy separation to commercial ones without chocking problem. The tested vortex generators were tangential and spiral types, which had single inducing channel with larger cross-sectional area than that of conventional multi-hole ones. The experimental result showed that the performance of the spiral type was better than that of the tangential one. As a small size of spiral one, the diameter of cold-end orifice is proposed to an half of tube diameter for the application to refrigeration system, while cold mass fraction ratio is 0.5∼0.6 for a desirable operation.
A Study on Areas of Application of a Extended Collision Model in a Wall Impaction Spray Calculation
Park, Gwon-Ha ; Jeong, Chang-Hwa ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1013~1020
DOI : 10.22634/KSME-B.2001.25.8.1013
This paper addresses to the area where the extended collision model is applied. In order to find the optimum shape of wall sprays, the extended model is applied to the nearest cells of just over the impaction wall, spray core or over all. The droplet distribution, wall spray radii, heights and gas flows are shown in all the cases. Those results show that the best spray shape represents in the case applying the extended model just on the impinging wall.
A Study on the Drop Formation of the Liquid Jet Device for Rapid Prototyping
Lee, U-Il ; Kim, Seon-Min ; Park, Jong-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1021~1029
DOI : 10.22634/KSME-B.2001.25.8.1021
Rapid prototyping(RP) is a novel technology to create 3D products directly from CAD system. This study proposes a new RP method which uses the PZT ceramic plate to make a Drop-On-Demand liquid jet from the nozzle. The characteristic of drop formation in the new system is investigated both numerically and experimentally. The optimal drop for 3-D Printing can be obtained by the proper amplitude and frequency of the applied voltage. Also the process of the drop formation is analyzed using the pressure wave theory and verified by numerical simulation. First, the pressure wave generated by the deformation of the Piezo-plate at the nozzle is analyzed by solving the 2D axisymmetric wave equation via Finite Element Method. Finally, the drop formation process is simulated using a commercial software, FLOW 3D considering the pressure at the nozzle obtained by solving the wave equation as the boundary condition.
The Study on the Gas Temperature Set by Calculating the Sensitivity of Slab Temperature in Reheating Furnace
Gang, Deok-Hong ; Kim, Gi-Hong ; Lee, Yong-Guk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1030~1036
DOI : 10.22634/KSME-B.2001.25.8.1030
A new mathematical model to determine the optimal gas temperatures in reheating furnace was proposed for the good quality of products. This model employs sensitivity method to calculate the optimal gas temperatures in each zone for heating the slab up to its discharging target temperature and for heating it uniformly. This method was validated by showing that the calculated discharging temperature of the slab was in a good agreement with its prescribed discharging target one through an off-line simulation.
Hysteresis Effects in Pool Boiling of Water
Gang, Myeong-Gi ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1037~1045
DOI : 10.22634/KSME-B.2001.25.8.1037
The effect of hysteresis in saturated pool boiling of water from stainless-steel surfaces has been investigated experimentally. Several sets of test sections of different surface conditions, geometries, orientations, diameters, lengths, and water types were tested at atmospheric pressure. The experimental results show that hysteresis effects in pool boiling heat transfer are not significant, but some appreciable trends are observed in accordance with parameters change. At higher heat flux regions, the curve for heat flux decrease is shifted to the left side of the curve for heat flux increase. To clarify hysteresis in pool boiling and to give some improvement on published correlations, four empirical correlations are obtained in terms of tube diameter, surface roughness, and tube wall superheat.
Correlations of Frost Properties Considering the Environmental Parameters over a Cold Flat Plate
Ji, Seong ; Lee, Gwan-Su ; Kim, Yong-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1046~1052
DOI : 10.22634/KSME-B.2001.25.8.1046
This study has been performed experimentally to measure the frost properties over a cold flat plate in order to obtain the correlations of the frost properties with various environmental parameters. Correlations of the frost surface temperature, thickness, density, and thermal conductivity are presented along with the experimental results as a function of environmental parameters, distance from the leading edge of test plate, and time. These correlations can be used to predict the frost properties with a maximum error of 8% in the following ranges : air temperature 15∼25
, relative humidity 60∼80%, air velocity 1∼3m/s and cooling plate temperature -15∼-25
Influence of Wavy Surface on the Turbulence in the Outer Layer
Na, Yang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1053~1059
DOI : 10.22634/KSME-B.2001.25.8.1053
Results from direct numerical simulation and LDV measurements are analyzed to investigate the influence of structured surface on turbulence in the outer layer. To provide a well-defined surface roughness, sinusoidal wavy surface was used. Even though flows over smooth and wavy surface show very different process for maintaining turbulence in the vicinity of the wall, there are some evidences that the turbulence in the outer layer has a universal characteristics and it may be possible to give a speculative interpretation that similarity of turbulent structures arises because Reynolds stress producing motion is similar regardless of different turbulence generation mechanisms embedded in both cases.
Large Scale Bursting Event in a Channel Flow
Na, Yang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1060~1067
DOI : 10.22634/KSME-B.2001.25.8.1060
A large-scale bursting event has been analyzed in a turbulent channel flow using a data obtained from a direct numerical simulation (DNS). Large-scale, plume-like structures have been frequently observed in many experimental results, but the origin of those structures is far from being fully understood. It is believed that those large scale events occur occasionally but contribute significantly to the generation of Reynolds shear stress in the outer layer. This paper attempts to give detailed examples of those large-scale motions observed in a turbulent channel flow at relatively low Reynolds number.
Relations of Near-Wall Streamwise Vortices to Wall Pressure Fluctuations in a Turbulent Boundary Layer
Seong, Hyeong-Jin ; Kim, Jung-Nyeon ; Choe, Jeong-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1068~1076
DOI : 10.22634/KSME-B.2001.25.8.1068
The relations between wall pressure fluctuations and near-wall streamwise vortices are investigated in a spatially-developing turbulent boundary layer using the direct numerical simulation. The power spectra and two-point correlations of wall pressure fluctuations are presented to validate the present simulation. Emphasis is placed on the identification of the correlation between wall pressure fluctuations and streamwise vorticities. It is shown that wall pressure fluctuations are directly linked with the upstream streamwise vortices in the buffer region of the turbulent boundary layer. The maximum correlation occurs with the spanwise displacement from the location of wall pressure fluctuations. The conditionally-averaged vorticity field and the quadrant analysis of Reynolds shear stress indicate that the sweep events due to streamwise vortices generate positive wall pressure fluctuations, while negative wall pressure fluctuations are created beneath the ejection events and vortex cores. The instantaneous flow field and time records reveal that the rise of high wall pressure fluctuations coincide with the passages of the upstream streamwise vortices.
Characteristics of Vortex Shedding behind a Circular Cylinder with Serrated Fins
Bu, Jeong-Suk ; Ryu, Byeong-Nam ; Kim, Gyeong-Cheon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1077~1086
DOI : 10.22634/KSME-B.2001.25.8.1077
An experimental study is performed to investigate the characteristics of vortex shedding behind a circular cylinder with serrated fins using hot-wire anemometer. Strouhal numbers which are calculated using outer diameter of a circular cylinder with serrated fins are higher than that of a circular cylinder. Fin thickness and pitch are closely related with vortex shedding frequency and play increasing or decreasing vortex shedding after transient Reynolds number. Strouhal numbers using effective diameters which are proposed in this paper agree with that of a circular cylinder. After transient Reynolds number, a trend of Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter.
Numerical Simulation of Unsteady CH
/Air Jet Diffusion Flame
Lee, Chang-Eon ; O, Chang-Bo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1087~1096
DOI : 10.22634/KSME-B.2001.25.8.1087
The dynamic structures of unsteady CH
/Air jet diffusion flame with a flame-vortex interaction were numerically investigated. A timed-dependent, axisymmetric computational model and a low mach number approximation were employed in the present calculation. A two-step global reaction mechanism which considers 6 species, was used to calculate the reaction rates. The predicted results including the gravitational effect show that the large outer vortices and the small inner vortices can be well simulated without any additional disturbances near nozzle tip. It was found that the temperature and species concentrations have deviated values even for the same mixture fraction in the flame-vortex interaction region. It was also shown that the flame surface is not deformed by the inner vortex in upstream region, while in downstream region, the flame surface is compressed or stretched by the outer vortex roll-up. The present unsteady jet flame configuration accompanying a flame-vortex interaction is expected to give good implications for the unsteady structures of turbulent flames.
A Study on the Design Technique of a 5-valve Combustion Chamber for Subcompact Vehicles
Lee, Gi-Hyeong ; Seong, Baek-Gyu ; Jeong, Yong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1097~1102
DOI : 10.22634/KSME-B.2001.25.8.1097
For the purpose of development of high performance gasoline engine, the design technique of the 5-valve(3 intake valves) combustion chamber for a subcompact vehicle has been studied. 3 intake valves cylinder heads were designed by using a 3-dimension CAD program, and steady state flow experiments have been performed with these model. The 5-valve engines, which have larger valve opening areas, have larger intake flow rates and higher flow coefficient than the 4-valve engines. The effects of intake port design parameters of a 5-valve engine on the intake flow rate and bore size were studied, and the design guidelines for the 5-valve engine were established.
Effect of Pressure Gradients on the Hairpin Structures in Turbulent Boundary Layers
Kim, Gyeong-Cheon ; Yun, Hong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1103~1112
DOI : 10.22634/KSME-B.2001.25.8.1103
The effect of pressure gradients on the hairpin structures in three different turbulent boundary layers (ZPG : Re(sub)
=910, FPG : Re(sub)
=575, APG : Re(sub)
=1290) has been examined with instantaneous velocity fields obtained in streamwise-wall-normal planes using PIV (particle image velocimetry) method. In the outer layer hairpin vortices occur in streamwise-aligned packets that propagate with small velocity dispersion. The signature pattern of the hairpin consists of a spanwise vortex core located above a region of strong second quadrant fluctuation (u<0 and v>0 : Q2 event) is clearly observed. The formation of packets explains the occurrence of multiple VITA events in turbulent burst. Noticeable differences are found in the average inclination angles of hairpin vortex packets which are 45
, and 51.9
in the case of ZPG, FPG and APG, respectively. It is found that the large, time-varying, irregularly shaped zones with nearly constant streamwise momentum exist throughout the boundary layer. Within the interior of the envelope the spatial coherence between the velocity fields induced by the individual vortices leads to strongly retarded streamwise momentum, explaining the zones of uniform momentum. The formation of the uniform momentum zone is remarkably different with respect to the pressure gradients especially in the logarithmic layer.
Nucleate Pool Boiling Heat Transfer in Vertical Annuli
Gang, Myeong-Gi ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1113~1121
DOI : 10.22634/KSME-B.2001.25.8.1113
Effects of gap sizes(3.9 and 15mm) of vertical annuli and the bottom blockage on the nucleate pool boiling heat transfer at atmospheric pressure condition have been examined experimentally, and the results were compared to those with a single tube without confinement. The annular geometry resulted in significant increase in heat transfer coefficient. The effect is much enhanced with the bottom blockage. The heat transfer coefficient for the closed bottom condition is three times greater than the unconfined tube at 30kW/㎡ when the gap size is 3.9mm. However, with further increase of the heat flux much more than 70kW/㎡, all these effects were diminished.
Film Cooling from Two Rows of Holes with Opposite Orientation Angles(I) -Configuration Effect-
An, Jun ; Jeong, In-Seong ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1122~1130
DOI : 10.22634/KSME-B.2001.25.8.1122
Film cooling performance from two rows of holes with opposite orientation angles is evaluated in terms of heat flux ratio. The film cooling hole has a fixed inclination angle of 35°and orientation angle of 45°for the downstream row and -45°for the upstream row. Four film cooling hole arrangements including inline and staggered configurations are investigated. The blowing ratio studied was 1.0. Boundary layer temperature distributions are measured to investigate injectant behaviors and mixing characteristics. Detailed distributions of the adiabatic film cooling effectiveness and the heat transfer coefficient are measured using TLC(Thermochromic Liquid Crystal). For the inline configuration, there forms a downwash flow at the downstream hole exit to make the injectant well attach to the wall, which gives high adiabatic film cooling effectiveness and heat transfer coefficient. The evaluation of heat flux ratio shows that the inline configuration gives better film cooling performance with the help of the downwash flow at the downstream hole exits.
Film Cooling from Two Rows of Holes with Opposite Orientation Angles(II) -Blowing Ratio Effect-
An, Jun ; Jeong, In-Seong ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1131~1139
DOI : 10.22634/KSME-B.2001.25.8.1131
Experimental results are presented, which describe the effect of blowing ratio on film cooling from two rows of holes with opposite orientation angles. The inclination angle is fixed at 35°, and the orientation angles are set to be 45°for the downstream row, and -45°for the upstream row. The studied blowing ratios are 0.5, 1.0 and 2.0. The boundary layer temperature distributions are measured using thermocouple at two downstream locations. Detailed adiabatic film cooling effectiveness and heat transfer coefficient distributions are measured with TLC(Thermochromic Liquid Crystal). The adiabatic film cooling effectiveness and heat transfer coefficient distributions are discussed in connection with the injectant behaviors inferred from the boundary layer temperature distributions. Film cooling performance, represented by heat flux is evaluated from the adiabatic film cooling effectiveness and heat transfer coefficient data. The results show that the investigated geometry provides improved film cooling performance at the high blowing ratios of 1.0 and 2.0.
Probing of Microscale Phase-Change Phenomena Based on Michelson Interforometry
Kim, Dong-Sik ; Park, Hui-Gwon ; Grigoropoulos, Costas-P. ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 8, 2001, Pages 1140~1147
DOI : 10.22634/KSME-B.2001.25.8.1140
Experimental schemes that enable characterization of phase-change phenomena in the microscale regime are essential for understanding the phase-change kinetics. Particularly, monitoring rapid vaporization on a submicron length scale is an important yet challenging task in a variety of laser-processing application, including steam laser cleaning and liquid-assisted material ablation. This paper introduces a novel technique based on Michelson interferometry for probing the liquid-vaporization process on a solid surface heated by a KrF excimer laser pulse(λ=248nm, FWHM=24ns) in water. The effective thickness of a microbubble layer has been measured with nanosecond time resolution. The maximum bubble size and growth rate are estimated to be of the order of 0.1㎛ and 1m/s, respectively. The results show that the acoustic enhancement in the laser induced vaporization process is caused by bubble expansion in the initial growth stage, not by bubble collapse. This work demonstrates that the interference method is effective for detecting bubble nucleation and microscale vaporization kinetics.