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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 36, Issue 12 - Dec 2012
Volume 36, Issue 11 - Nov 2012
Volume 36, Issue 10 - Oct 2012
Volume 36, Issue 9 - Sep 2012
Volume 36, Issue 8 - Aug 2012
Volume 36, Issue 7 - Jul 2012
Volume 36, Issue 6 - Jun 2012
Volume 36, Issue 5 - May 2012
Volume 36, Issue 4 - Apr 2012
Volume 36, Issue 3 - Mar 2012
Volume 36, Issue 2 - Feb 2012
Volume 36, Issue 1 - Jan 2012
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Shape Optimization of Impeller Blades for Bidirectional Axial Flow Pump
Baek, Seok Heum ; Jung, Won Hyuk ; Kang, Sangmo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1141~1150
DOI : 10.3795/KSME-B.2012.36.12.1141
This paper describes the shape optimization of impeller blades for an anti-heeling bidirectional axial flow pump used in ships. In general, a bidirectional axial pump has efficiency much lower than that of a classical unidirectional pump because of the symmetry of the blade type. In this study, by focusing on a pump impeller, the shape of the blades is redesigned to develop a bidirectional axial pump with higher efficiency. The commercial code employed in this simulation is CFX v.13. The CFD result of the pump torque, head, and hydraulic efficiency was compared. The orthogonal array (OA) and analysis of variance (ANOVA) techniques and surrogate-model-based optimization using orthogonal polynomials are employed to determine the main effects and their optimal design variables. According to the optimal design, we confirm an effective design variable for impeller blades and explain the optimal solution as well as the usefulness of satisfying the constraints of the pump torque and head.
Experimental and Numerical Analysis of DME Spray Characteristics in Common-rail Fuel System
Jeong, Soo-Jin ; Park, Jung-Kwon ; Lee, Sang-In ; Lim, Ock-Taeck ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1151~1159
DOI : 10.3795/KSME-B.2012.36.12.1151
Spray visualization and computer simulation of a DME injector have been conducted to investigate the enlarged injection hole diameter effect. To increase the reliability of the computational result, simulation results have been compared with the visualization test results, and the behaviors of a DME spray under various high-pressure and -temperature conditions have been computed. This study shows a discrepancy of 3.57% between the experimental and the computational results of penetration length for an injection pressure of 35 MPa and ambient pressure of 5 MPa. When simulating the engine conditions, the maximum penetration length of a fully developed DME spray is 42 mm when the temperature to pressure ratio is 300 K/MPa. The DME spray behavior is dominantly affected by the ambient pressure under the condition that the ratio is less than 300 K/MPa, and by the ambient temperature under the condition that the ratio is more than 300 K/MPa.
Aerodynamic Characteristics and Wing Tip Vortex Behavior of Three-Dimensional Symmetric Wing According to Heights
Yoo, Younghyun ; Lee, Sanghwan ; Lee, Juhee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1161~1169
DOI : 10.3795/KSME-B.2012.36.12.1161
A numerical study has been conducted to investigate the aerodynamic characteristics and behavior of a wing-tip vortex around a three-dimensional symmetric wing (NACA0015) in the vicinity of the ground. The aerodynamic characteristics and the wing-tip vortex change as a wing approaches the ground as a result of two different phenomena: the ground effect and the Venturi effect. The ground effect increases lift and decreases drag whereas the Venturi effect generates negative lift and increases drag suddenly. A symmetric airfoil experiences both phenomena with respect to changes in the angle of attack. In the case of a NACA0015 airfoil, the Venturi effect is dominant at small angles of attack but the ground effect is dominant at large angles of attack. Interestingly, both phenomena can be observed at the 4 degree of angle of attack. The vortex core moves inside a wing when the wing experiences the Venturi effect, whereas the vortex core moves outward when the wing experiences the ground effect.
Laser Patterning of Vertically Grown Carbon Nanotubes
Chang, Won Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1171~1176
DOI : 10.3795/KSME-B.2012.36.12.1171
The selective patterning of a carbon nanotube (CNT) forest on a Si substrate has been performed using a femtosecond laser. The high shock wave generated by the femtosecond laser effectively removed the CNTs without damage to the Si substrate. This process has many advantages because it is performed without chemicals and can be easily applied to large-area patterning. The CNTs grown by plasma-enhanced chemical vapor deposition (PECVD) have a catalyst cap at the end of the nanotube owing to the tip-growth mode mechanism. For the application of an electron emission and biosensor probe, the catalyst cap is usually removed chemically, which damages the surface of the CNT wall. Precise control of the femtosecond laser power and focal position could solve this problem. Furthermore, selective CNT cutting using a femtosecond laser is also possible without any phase change in the CNTs, which is usually observed in the focused ion beam irradiation of CNTs.
Development of Optimal Control of Heliostat System Using Configuration Factor and Solar Tracking Device
Lee, Dong Il ; Jeon, Woo Jin ; Baek, Seung Wook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1177~1183
DOI : 10.3795/KSME-B.2012.36.12.1177
This study aims to develop a system that maximizes the radiative heat transfer from the heliostat to the receiver by using the configuration factor and a solar tracking device. As the heat transfer from the heliostat to the receiver is delivered by solar radiation, the configuration factor commonly utilized for radiation is applied to control the heliostat. Tracking the sun and calculating its position are possible by using an illuminance sensor (CdS) and Simulink. By applying optimized algorithms programmed using Simulink that maximize the configuration factors among the heliostat, receiver, and sun in real time, the solar absorption efficiency of the receiver can be maximized. Simulations were performed on how to change the angle required to control the elevation and azimuthal angle of the heliostat during the daytime with respect to various distances.
Dynamic Modeling of Cooling System Thermal Management for Automotive PEMFC Application
Han, Jae Young ; Lee, Kang Hun ; Yu, Sang Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1185~1192
DOI : 10.3795/KSME-B.2012.36.12.1185
The typical operating temperature of an automotive fuel cell is lower than that of an internal combustion engine, which necessitates a refined strategy for thermal management. In particular, the performance of the cooling module has to be higher for a fuel cell system because the temperature difference between the fuel cell and the surrounding is lower than in the case of the internal combustion engine. Even though the cooling system of an automotive fuel cell determines the operating temperature and temperature distribution of the fuel cell, it has attracted little research attention. This study presents the mathematical model of a cooling system for an automotive fuel cell system using Matlab/
. In particular, a radiator model is developed for design optimization from the development stage to the operating stage for an automotive fuel cell. The cooling system model comprises a fan, pump, and radiator. The pump and fan model have an empirical relation, and the dynamics of the pump and fan are only explained by motor dynamics. The basic design study was conducted, and the geometric setup of the radiator was investigated. When the control logic was applied, the pump senses the coolant inlet temperature and the fan senses the coolant out temperature. Additionally, the cooling module is integrated with the fuel cell system model so that the performance of the cooling module can be investigated under realistic operating conditions.
Flame Instability in Heptane Pool Fires Near Extinction
Jeong, Tae Hee ; Lee, Eui Ju ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1193~1199
DOI : 10.3795/KSME-B.2012.36.12.1193
A cup burner experiment was performed to investigate the effect of the oxidizer velocity and concentration on flame instability near extinction. Heptane was used as a fuel and air diluted by nitrogen and carbon dioxide was used in the oxidizer stream. Two types of flame instabilities at the flame base and at axial downstream were observed near extinction. The instability at the flame base could be characterized by cell, swing, and rotation modes, and the cell mode changed to the rotation mode through the swing mode as the oxidizer velocity increased. To assess the parameters for the flame instability, the initial mixture strengths, Lewis number, and adiabatic flame temperature were investigated under each condition. The Lewis number might be the most important among them, but it is impossible to generalize because of the insufficient number of cases. Furthermore, the axial periodic flickering motion disappeared at low and high oxidizer velocities near extinction. This resulted from the fact that low oxidizer velocity induced evaporated fuel velocity below the critical velocity and high velocity made the reacting fuel velocity comparable.
Effects of Impeller Shape of Submersible Nonclogging Pump on its Performance
Yun, Jeong-Eui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1201~1207
DOI : 10.3795/KSME-B.2012.36.12.1201
This study was performed to develop a high-efficiency submersible nonclogging pump impeller. Toward this end, we simulated the effect of some parameters such as the outlet position of a blade (
), outlet width of a blade (
), and hub profile on the pump efficiency by using the commercial codes ANSYS CFX and BladeGen. The results showed that the pump efficiency was proportional up to
= 38 mm and
= 55 mm. It remained constant over these values. However, the head and shaft power were proportional to
in the simulated ranges. The effects of hub profile changes on the pump efficiency were relatively small compared to those of the other parameters.
Transition Phenomenon from a Flat Flame to Turbulent Flame Motions by External Laser
Park, June Sung ; Choi, Byung Chul ; Fujita, Osamu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1209~1215
DOI : 10.3795/KSME-B.2012.36.12.1209
Experiments with premixed flames in a tube have been conducted to investigate the transition phenomenon from a laminar flat flame to turbulent motions. To induce this phenomenon, a flat flame is formed in a tube. Then, the local velocity at the center of the flat flame surface is increased using
laser irradiation. The deformed flame front propagates with an increase in the total flame surface and oscillating instability. Eventually, the flame front accelerates explosively, and it shows turbulent flame motions with a strong noise. The dynamic behaviors of the flame front prior to the turbulent motions are analyzed in this study to elucidate this process. The physical model of the process is presented according to observations.
Development of Wall Flow Sensor Using Micro Imaging Device
Lee, Seung Hwan ; Kim, Byung Soo ; Kim, Hyoung-Bum ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 12, 2012, Pages 1217~1222
DOI : 10.3795/KSME-B.2012.36.12.1217
A wall flow sensor has been used for feedback flow control and wall shear stress measurement. In this study, we developed a new wall flow sensor by combining the PIV algorithm and the micro image sensor used in an optical mouse. The feasibility of the wall flow sensor was investigated by using simulated fluid flow experiments. Compared with the quadrature signal from imaging devices, the accuracy of the wall flow velocity measurement was improved and the dynamic range increased. In addition, the depth information of particles was also measured by using the defocusing imaging technique.