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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Marine Engineering
Journal Basic Information
Journal DOI :
Korean Society of Marine Engineers
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Volume & Issues
Volume 35, Issue 8 - Nov 2011
Volume 35, Issue 7 - Nov 2011
Volume 35, Issue 6 - Sep 2011
Volume 35, Issue 5 - Jul 2011
Volume 35, Issue 4 - May 2011
Volume 35, Issue 3 - May 2011
Volume 35, Issue 2 - Mar 2011
Volume 35, Issue 1 - Jan 2011
Selecting the target year
Experimental Analyses of Cell Voltages for a Two-cell PEM Stack Under Various Operating Conditions
Park, Sang-Kyun ; Choi, Jae-Hyuk ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 881~890
DOI : 10.5916/jkosme.2011.35.7.881
Analyses of performance and behavior of the individual PEM fuel cells (PEMFC) under different operating conditions are of importance optimally to design and efficiently to operate the stack. The paper focuses on experimental analyses of a two-cell stack under different operating conditions, which performance and behavior are measured by the voltage of a cell as well as the stack. Experimental parameters include stoichiometric ratio, temperature of the air supplied under different working stack temperatures and loads. Results showed that the cell voltages are dominantly influenced by the temperature of the air supplied among others. In addition, an inherent difference between the first and the second cell voltage exists because of the tolerances of the cell components and the resulting different over-potentials at different equilibrium states. Furthermore, it is shown that the proton conductivity in the membranes conditioned by the humidity in the cathode channel highly affects the voltage differences of the two cells.
Optimal Design of Compact Heat Exchanger (Louver Fin-tube Heat Exchanger for High Heat Transfer and Low Pressure Drop)
Kang, Hie-Chan ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 891~898
DOI : 10.5916/jkosme.2011.35.7.891
The present work was conducted to get the best geometric information for the optimum design of the complex heat exchanger. The objective function for optimal design was expressed as a combination of pressure drop and heat transfer rate. The geometric parameters for the variables of louver pitch and height, tube width, etc., were limited to ranges set by manufacturing conditions. The optimum geometric parameters were calculated by using empirical correlations and theory. The sensitivity of the parameters and optimum values are shown and discussed. The weighting factor in the objective function is important in the selection of the louver fin-tube heat exchanger.
Characteristic of Fatigue Crack Behavior on the Mixed-Mode in Aluminum Alloy 5083-O
Kim, Gun-Ho ; Cho, Kyu-Chun ; Lee, Ho-Yeon ; Won, Young-Jun ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 899~906
DOI : 10.5916/jkosme.2011.35.7.899
Generally, load conditions of machine or structure in fatigue destruction is occurred not under single load conditions but under mixed load conditions. However, the experiment under mixing mode is insufficient because of no having test standard to the behavior of crack under mixing mode and variety of test methods, and many tests are required. In this paper measured crack direction path by created figure capture system when a experiment. Also, we studied by comparison the behavior of crack giving the change of stress ratio and inserting beach mark. Through the test under mixing mode, advancing path of crack is indicated that advancing inclined angle
(direction of specimen length) has increased depending on the increase of mixed mode impaction. It is indicated that according to the increase of mixed mode loading condition impaction under mixing mode, advancing speed of crack gets slow. Also, we found that inner crack(cross section of specimen) is progressed more rapidly than outer crack based on data through beach mark.
Experimental Studies on Swirling Flow in a Vertical Circular Tube
Chang, Tae-Hyun ; Lee, Chang-Hoan ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 907~913
DOI : 10.5916/jkosme.2011.35.7.907
Swirling flows are related to the spiral motion in the tangential direction in addition to the axial and radial direction using several swirl generators. These type of flows are used in combustion chambers to improve flame stability, heat exchanger to enhance heat transfer coefficients, agricultural spraying machines and some vertical pipes to move slurries or transport of materials. However, only a few studies three dimensional velocity profiles in a vertical pipe have been reported. In this present paper, 3 dimension particle image velocimetry(PIV) technique was employed to measure the velocity profiles in water along a vertical circular pipe with Reynolds number from 6000 to 13,000. A tangential inlet condition was used as the swirl generator to produce the required flow. The velocities were measured with swirling flow in the water along the test section using the PIV technique.
Effect of Venturi System on Acceleration of Low-speed Water Flow at the Venturi Throat Installed at the Inlet of Hydro Turbine
Jung, Sang-Hoon ; Seo, In-Ho ; Kim, Chul-Ho ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 914~920
DOI : 10.5916/jkosme.2011.35.7.914
For a hydro turbine electricity generation system in river or bay, a venturi system could be applied to accelerate flow speed at the inlet of the turbine system in a flow field. In this study, a steady flow simulation was conducted to understand the effect of venturi system on the acceleration of current speed at the inlet of a hydro turbine system. According to the continuity equation, the flow speed is inversely proportional to the cross-section area in a conduit flow; however, it would be different in an open region because the venturi system would be an obstruction in the flow region. As the throat area is 1/5 of the inlet area of the venturi, the flow velocity is accelerated up to 2.1 times of the inlet velocity. It is understood that the venturi system placed in an open flow region gives resistance to the upcoming flow and disperses the flow energy around the venturi system. The result of the study should be very important information for an optimum design of a hydro turbine electricity generation system.
Measurement of Fluid Dynamic Characteristics around Stenotic Obstruction in a Circular Channel
An, Jin-Hyo ; Cheema, T.A. ; Jeong, Seong-Ryong ; Lee, Choon-Young ; Kim, Gyu-Man ; Park, Cheol-Woo ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 921~929
DOI : 10.5916/jkosme.2011.35.7.921
We measured experimentally the properties of fluid dynamics, velocity fields, and the pressure, around stenotic obstruction located inside a circular channel structure. Particle image velocimetry system was employed to obtain velocity fields at the central section of the circular channel in the streamwise direction. The stenosis model used was made of acrylic material with different stenotic aspect ratios. The working fluid was water and it was returned by a centrifugal pump system. Pressure measurements were carried out to validate the effect of a narrow passageway. Results showed that the acceleration of gap flow through stenotic obstruction and the pressure drop in the recirculation regime behind the stenosis model can be observed.
Turbulence Characteristics in a Circular Open Channel by PIV Measurements
Kim, Sun-Gu ; Sung, Jae-Yong ; Lee, Myeong-Ho ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 930~937
DOI : 10.5916/jkosme.2011.35.7.930
The characteristics of mean velocity and turbulence have been analyzed in the circular open channel flow using PIV measurement data for a wide range of water depth. The measured data are fitted to a velocity distribution function over the whole depth of the open channel. Reynolds shear stress and mean velocity in wall unit are compared with the analytic models for fully-developed turbulent boundary layer. Both the mean velocity and Reynolds shear stress have different distributions from the two-dimensional boundary layer flow when the water depth increases over 50% since the influence of the side wall penetrates more deeply into the free surface. The cross-stream Reynolds normal stress also has considerably different distribution in view of its peak value and decreasing rate in the outer region whether the water depth is higher than 50% or not.
On the Significance of Turbulence Models and Unsteady Effect on the Flow Prediction through A High Pressure Turbine Cascade
El-Gendi, M.M. ; Lee, Sang-Wook ; Son, Chang-Ho ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 938~945
DOI : 10.5916/jkosme.2011.35.7.938
Unsteady flow simulations through a transonic turbine vane were carried out for an isentropic Mach number of 1.02 and a Reynolds number of
. The main objective of the study is to investigate the effect of unsteadiness due to vortex shedding on the flow in transonic regime. The steady and the time-averaged unsteady results by employing three different turbulence models: shear stress transport (SST), k-
Reynolds stress models were compared. The comparisons were emphasized on the isentropic Mach number along the blade and total pressure loss at the cascade exit. The results showed that both steady and unsteady calculations have good agreement with experimental data along the blade surface. However, at cascade exit, the unsteady calculations have much better agreement with experimental data than steady calculations. Based on these, we conclude that the unsteady flow calculations are essential for these types of problems.
On the Application of CFD Codes for Natural Gas Dispersion and Explosion in Gas Fuelled Ship
Kim, Ki-Pyoung ; Kang, Ho-Keun ; Choung, Choung-Ho ; Park, Jae-Hong ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 946~956
DOI : 10.5916/jkosme.2011.35.7.946
The main objectives of this study are to analyze the leaked gas dispersion and quantify the potential overpressures due to vapor cloud explosions in order to identify the most significant contributors to risk by using Computational Fluid Dynamics (CFX & FLACS) for gas fuelled ships. A series of CFD simulations and analyses have been performed for the various gas release scenarios in a closed module, covering different release rates and ventilating methods. This study is specially focused on the LNG FGS (Fuel Gas Supply) system recently developed for the propulsion of VLCC crude oil carriers by shipyards. Most of work presented is discussed on the gas dispersion from leaks in the FGS room, and shows some blast prediction validation examples.
Investigations into the Cylinder Flow Stabilities with a Thin Film Attachment
Doh, Deog-Hee ; Jo, Hyo-Je ; Kwon, Seang-Yong ; Kim, Hyoung-June ; Cho, Gyeang-Rae ; Shin, Byeong-Rog ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 957~965
DOI : 10.5916/jkosme.2011.35.7.957
The wakes of a cylindrical body have been investigated. The cylindrical body was attached with a thin film. The film is made of silicon with configurations of 50mm(W)
0.3mm(T). The cylinder wakes have been measured with PIV experiments under the conditions with and without the thin film. The diameter of the installed cylinder body is 30mm and the Reynolds numbers are 2730, 6160 and 9750 with the diameter. The measurement system consists of an Ar-ion laser(6W), a high speed camera(1024
992 pixel, 500fps) and a host computer. FFT analyses have been carried out using the velocity vectors obtained by PIV measurements at the point X/D=1.52 and Z/D=0.52. For understanding the three-dimensional flow structures, a new Volumetric PTV(particle tracking velocimetry) has been constructed, in which the same four high-resolution cameras have been used. It has been verified that the flexible film suppresses or damps the vortices separated from the cylinder body, which makes the cylinder's wakes stable. With increase of Re numbers the intensity of the dominant frequency of the wakes become smaller.
Analysis on How to Locate the Maximum Line Voltage to Hull in Steady State on the Vector Diagram Onboard Vessels
Choi, Soon-Man ;
Journal of the Korean Society of Marine Engineering, volume 35, issue 7, 2011, Pages 966~973
DOI : 10.5916/jkosme.2011.35.7.966
Power distribution onboard vessel is typically configured as ungrounded system due to the ability to continuously supply electric power even when an earth fault occurs. The impedance connections between 3 phase power lines and hull cause the line-to-hull voltages to become unstable and increased in case the impedances are unbalanced, bringing the situation susceptible to electric shock and deterioration of insulation material. Also the line-to-hull voltage can reach to a certain maximum value in the steady state depending on the distributed capacitances and grounding resistances between lines and hull. This study suggests how to find and calculate the maximum line-to-hull voltage in view of magnitude and phase angle based on the vector diagram.