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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
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 33, Issue 12 - Dec 2009
Volume 33, Issue 11 - Nov 2009
Volume 33, Issue 10 - Oct 2009
Volume 33, Issue 9 - Sep 2009
Volume 33, Issue 8 - Aug 2009
Volume 33, Issue 7 - Jul 2009
Volume 33, Issue 6 - Jun 2009
Volume 33, Issue 5 - May 2009
Volume 33, Issue 4 - Apr 2009
Volume 33, Issue 3 - Mar 2009
Volume 33, Issue 2 - Feb 2009
Volume 33, Issue 1 - Jan 2009
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Numerical Analysis of Partial Cavitaing Flow Past Axisymmetric Cylinders
Kim, Bong-Su ; Lee, Byung-Woo ; Park, Warn-Gyu ; Jung, Chul-Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 69~78
DOI : 10.3795/KSME-B.2009.33.2.69
Cavitating flow simulation is of practical importance for many hydraulic engineering systems, such as pump, turbine, nozzle, injector, etc. In the present work, a solver for cavitating flow has been developed and applied to simulate the flows past axisymmetric cylinders. Governing equations are the two-phase Navier-Stokes equations, comprised of continuity equation of liquid and vapor phase. The momentum equation is in the mixture phase. The solver employed an implicit, dual time, preconditioned algorithm in curvilinear coordinates. Computations were carried out for three axisymmetric cylinders: hemispherical, ogive, and caliber-0 forebody shape. Then, the present calculations were compared with experiments and other numerical results to validate the present solver. Also, the code has shown its capability to accurately simulate the re-entrant jet phenomena and ventilated cavitation. Hence, it has been found that the present numerical code has successfully accounted for cavitating flows past axisymmetric cylinders.
Reduction of Flow-Induced Noise in an Expansion Muffler with Lids
Kang, Woong ; Kim, Hyung-Jin ; Sung, Hyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 79~84
DOI : 10.3795/KSME-B.2009.33.2.79
Turbocharger has been widely used in many passenger cars in application with diesel engines because of high power and fuel efficiency. However, flow-induced noise (whoosh or hissing noise) which is generated within a compressor during its operation at marginal surge line can deteriorate noise characteristics. Hissing noise excitation is associated with the generation of turbulence within the turbocharger compressor and radiated through the transmission path in a turbocharger system. In this study, a expansion muffler with lids is devised and installed in the transmission path to reduce the hissing noise. Acoustic and fluid dynamic characteristics for the muffler are investigated which are related to the unsteadiness of turbulence and pressure in the turbocharger system. A transfer matrix method is used to analyze the transmission loss of the muffler. A simple expansion muffler with lids is proposed for the reduction of high frequency component noise. Turbulence simulation is carried out by a standard k -
model. An optimal design condition of the muffler is obtained by extensive acoustic and fluid dynamic analysis on the engine dynamometer with anechoic chamber. A significant reduction of the hissing noise is achieved at the optimal design of the muffler as compared with the conventional muffler.
Experimental and Numerical Assessment of Liquid Water Exhaust Performance of Flow Channels in PEM Fuel Cells
Kim, Hyun-Il ; Nam, Jin-Hyun ; Shin, Dong-Hoon ; Chung, Tae-Yong ; Kim, Young-Gyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 85~92
DOI : 10.3795/KSME-B.2009.33.2.85
Polymer electrolyte membrane (PEM) fuel cells are a promising technology for short-term power generation required in residential and automobile applications. Proper management of water has been found to be essential for improving the performance and durability of PEM fuel cells. This study investigated the liquid water exhaust capabilities of various flow channels having different geometries and surface properties. Three-pass serpentine flow fields were prepared by patterning channels of 1 mm or 2 mm width onto hydrophilic Acrylic plates or hydrophobic Teflon plates, and the behaviors of liquid water in those flow channels were experimentally visualized. Computational fluid dynamics (CFD) simulations were also conducted to quantitatively assess the liquid water exhaust capabilities of flow channels for PEM fuel cells. Numerical results showed that hydrophobic flow channels have better liquid water exhaust capabilities than hydrophilic flow channels. Flow channels with curved corners showed less droplet stagnation than the channels with sharp corners. It was also found that a smaller width is desirable for hydrophobic flow channels while a larger width is desirable for hydrophilic ones. The above results were explained as being due to the different droplet morphologies in hydrophobic and hydrophilic channels.
Study of Micro-Supersonic Impinging Jets and Its Application to the Laser Machining
Min, Seong-Kyu ; Yu, Dong-Ok ; Lee, Yeol ; Cheong, Jo-Soon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 93~100
DOI : 10.3795/KSME-B.2009.33.2.93
Characteristics of micro-sonic/supersonic axi-symmetric jet impinging on a flat plate with a pre-drilled hole were both experimentally and numerically studied, to observe the role of assist-gas jet to eject melted materials from the cut zone in the laser machining. For various Mach numbers of the nozzle and the total pressures of the assist gas, detailed impinging jet flow structures over the plate and the variations of mass flux through the pre-drilled hole were observed. It was found that the present experimental and numerical results show a good agreement, which proves the accountability of the present work. From the present study, it was also observed that the mass flow rate through the hole was closely related with the total pressure loss caused by the Mach disc on the work piece, and that supersonic nozzle could perform more efficient roles as blowing the assist-gas jet in the laser machining, as compared to sonic nozzles.
Disjoining Pressures of Nanoscale Thin Films on Solid Substrate
Han, Min-Sub ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 101~106
DOI : 10.3795/KSME-B.2009.33.2.101
The disjoining pressure is an important physical property in modeling the small-scale transport phenomena on thin film. It is a very useful definition in characterizing the non-continuum effects that are not negligible in heat and mass transport of the film thinner than submicro-scales. We present the calculated values of disjoining pressure of He, Kr and Xe thin films absorbed on graphite substrate using Molecular Dynamics Simulation (MD). The disjoining pressure is accurately calculated in the resolution of a molecular scale of the film thickness. The characteristics of the pressure are discussed regarding the molecular nature of the fluid system such as molecular diameter and intermolecular interaction parameters. The MD results are also compared with those based on the continuum approximation of the slab-like density profile and the results on other novel gases in the previous study. The discrepancies of the continuum model with MD results are shown in all three configurations and discussed in the view point of molecular features.
Numerical Study on Aerodynamic Characteristic of the Moving Circular Cylinder Near the Wavy Wall
Kim, Hyung-Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 107~115
DOI : 10.3795/KSME-B.2009.33.2.107
A Computational study was carried out in order to investigate the aerodynamic characteristics of circular cylinder moving near the wavy wall at a low Reynolds number of 50. Lattice Boltzmann method was used to simulate the flow field and immersed boundary method was combined to represent the moving cylinder and wavy wall regardless of the constructed grid in the domain. The aerodynamics characteristics of the cylinder moving near the wavy wall were represented by the comparing the lifting coefficients with various altitudes (H/D) and wave length and amplitudes of wavy wall. It indicated that the twice of increasing-decreasing variations of lifting coefficient are obtained while the cylinder moves near the wavy wall. The first variation is obtained where the cylinder locates near the peak of the wavy wall. Another variation occurs when the distance to the wavy wall becomes longer after passing the peak. It was also classified that three different patterns of relation between the lifting and drag coefficient of the cylinder. However, the classification is limited to the case of the same order of altitude, amplitude and wave length of the wavy wall.
Pt Coating on Flame-Generated Carbon Particles
Choi, In-Dae ; Lee, Dong-Geun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 116~123
DOI : 10.3795/KSME-B.2009.33.2.116
Carbon black, activated carbon and carbon nanotube have been used as supporting materials for precious metal catalysts used in fuel cell electrodes. One-step flame synthesis method is used to coat 2-5nm Pt dots on flame-generated carbon particles. By adjusting flame temperature, gas flow rates and resident time of particles in flame, we can obtain Pt/C nano catalyst-support composite particles. Additional injection of hydrogen gas facilitates pyrolysis of Pt precursor in flame. The size of as-incepted Pt dots increases along the flame due to longer resident time and sintering in high temperature flame. Surface coverage and dispersion of the Pt dots is varied at different sampling heights and confirmed by Transmission electron microscopy (TEM), Energy-dispersive spectra (EDS) and X-ray diffraction (XRD). Crystalinity and surface bonding groups of carbon are investigated through X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.
Fluid-elastic Instability in a Tube Array Subjected to Two-Phase Cross Flow
Sim, Woo-Gun ; Park, Mi-Yeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 124~132
DOI : 10.3795/KSME-B.2009.33.2.124
Experiments have been performed to investigate fluid-elastic instability of tube bundles, subjected to twophase cross flow. Fluid-elastic is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and the threshold flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.
Development of Fast-Response CO
Analyzer and Analysis of Engine-out Emission during Cold Start of SI Engine
Song, Hyun-Soo ; Park, Kyoung-Seok ; Park, Dong-Sun ; Min, Kyoung-Doug ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 133~140
DOI : 10.3795/KSME-B.2009.33.2.133
analyzer has been developed for measuring the
concentration during transient condition of a SI engine. The analyzer consists of the non-dispersive infrared absorption method, electrical chopping system and water cooling system. The analyzer has good repeatability, linearity and permissible drift characteristic. Besides, it showed 18ms of a response to measure the
concentration. The fast-response
analyzer was applied to a single cylinder SI engine and the
emission was examined during engine start. Simultaneously, the standard exhaust gas analyzer, which has slow response time, was used for confirming the accuracy of the exhaust gas analysis using the fast-response
analyzer. The developed analyzer showed much faster responsive characteristic than that of a standard analyzer and made cycle by cycle exhaust gas analysis possible. The transient engine operating characteristics will be estimated from the
concentration of engine-out emissions and engine operating variables.
Development of Performance Analysis Program for an Axial Compressor with Meanline Analysis
Park, Jun-Young ; Park, Moo-Ryong ; Choi, Bum-Suk ; Song, Je-Wook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 33, issue 2, 2009, Pages 141~148
DOI : 10.3795/KSME-B.2009.33.2.141
Axial-flow compressor is one of the most important parts of gas turbine units with axial turbine and combustor. Therefore, precise prediction of performance is very important for development of new compressor or modification of existing one. Meanline analysis is a simple, fast and powerful method for performance prediction of axial-flow compressors with different geometries. So, Meanline analysis is frequently used in preliminary design stage and performance analysis for given geometry data. Much correlations for meanline analysis have been developed theoretically and experimentally for estimating various types of losses and flow deviation angle for long time. In present study, meanline analysis program was developed to estimate compressor losses, incidence angles, deviation angles, stall and surge conditions with many correlations. Performance prediction of one stage axial compressors is conducted with this meanline analysis program. The comparison between experimental and numerical results show a good agreement. This meanline analysis program can be used for various types of single stage axial-flow compressors with different geometries, as well as multistage axial-flow compressors.