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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 38, Issue 12 - Dec 2014
Volume 38, Issue 11 - Nov 2014
Volume 38, Issue 10 - Oct 2014
Volume 38, Issue 9 - Sep 2014
Volume 38, Issue 8 - Aug 2014
Volume 38, Issue 7 - Jul 2014
Volume 38, Issue 6 - Jun 2014
Volume 38, Issue 5 - May 2014
Volume 38, Issue 4 - Apr 2014
Volume 38, Issue 3 - Mar 2014
Volume 38, Issue 2 - Feb 2014
Volume 38, Issue 1 - Jan 2014
Selecting the target year
An Experimental Study on Performance of Second Throat Exhaust Diffusers of Different Configuration
Jeon, Jun Su ; Kim, Wan Chan ; Yeoun, Hae In ; Kim, Min Sang ; Ko, Young Sung ; Han, Young Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 279~288
DOI : 10.3795/KSME-B.2014.38.4.279
Second throat supersonic exhaust diffusers (STEDs) were designed to simulate high-altitude conditions according to the normal-shock model. Experimental studies were performed on the STEDs to investigate how performance characteristics varied with the length and diameter of the STED using high-pressure nitrogen gas. The variation in performance due to length indicated that the performance of the STED could be very slightly improved by adjusting the diffuser inlet length (
), and it could be significantly improved by optimizing the second throat length ratio (
) and the divergence length (
). The starting and vacuum chamber pressures exhibited the highest level of performance near (
) of the design point.
Multi-MW Class Wind Turbine Blade Design Part I : Aero-Structure Design and Integrated Load Analysis
Kim, Bum Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 289~309
DOI : 10.3795/KSME-B.2014.38.4.289
A rotor blade is an important device that converts kinetic energy of wind into mechanical energy. Rotor blades affect the power performance, energy conversion efficiency, and loading and dynamic stability of wind turbines. Therefore, considering the characteristics of a wind turbine system is important for achieving optimal blade design. This study examined the general blade design procedure for a wind turbine system and aero-structure design results for a 2-MW class wind turbine blade (KR40.1b). As suggested above, a rotor blade cannot be designed independently, because its ultimate and fatigue loads are highly dependent on system operating conditions. Thus, a reference 2-MW wind turbine system was also developed for the system integrated load calculations. All calculations were performed in accordance with IEC 61400-1 and the KR guidelines for wind turbines.
Multi-MW Class Wind Turbine Blade Design Part II : Structural Integrity Evaluation
Kim, Bum Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 311~320
DOI : 10.3795/KSME-B.2014.38.4.311
Rotor blades are important devices that affect the power performance, efficiency of energy conversion, and loading and dynamic stability of wind turbines. Therefore, considering the characteristics of a wind turbine system is important for achieving optimal blade design. When a design is complete, a design evaluation should be performed to verify the structural integrity of the proposed blade in accordance with international standards or guidelines. This paper presents a detailed exposition of the evaluation items and acceptance criteria required for the design certification of wind turbine blades. It also presents design evaluation results for a 2-MW blade (KR40.1b). Analyses of ultimate strength, buckling stability, and tip displacement were performed using FEM, and Miner's rule was applied to evaluate the fatigue life of the blade. The structural integrity of the KR40.1b blade was found to satisfy the design standards.
Performance Characteristics Under Non-Reacting Condition with Respect to Length of a Subscale Diffuser for High-Altitude Simulation
Jeong, Bonggoo ; Kim, Hong Jip ; Jeon, Junsu ; Ko, Youngsung ; Han, Yeoung-Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 321~328
DOI : 10.3795/KSME-B.2014.38.4.321
The performance characteristics of a subscale diffuser under non-reacting conditions for high-altitude simulation were numerically investigated with respect to different lengths of the secondary throat diffuser. The ratio of the length of the diffuser entrance to the nozzle exit diameter was set to 0, 50, and 100%. In addition, flow characteristics were studied for a range of length-to-diameter ratios of the secondary throat diffuser. An insufficient diffuser entrance length caused contraction of the plume immediately after the nozzle exit. When the length-to-diameter ratio was less than 8, a strong Mach disk was formed inside the diffuser, resulting in a sharp increase in pressure. In addition, flow characteristics in the diverging part of the diffuser were investigated for a range of diverging part lengths. A short diverging part may lead to abrupt pressure recovery, resulting in the possible application of mechanical load to the diffuser.
Study on the Pattern of Internal Flow inside a water droplet placed on Vibrating Hydrophobic Surface
Kim, Hun ; Shin, Young Sub ; Lim, Hee Chang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 329~335
DOI : 10.3795/KSME-B.2014.38.4.329
This study aimed to understand the internal flow characteristics of a liquid droplet subject to periodic forced vibration. In order to predict the resonance frequency of a droplet, a high-speed camera and macro lens were used to capture internal flow characteristics of a droplet placed on a vibrating hydrophobic surface. Results showed that the droplet assumed a variety of shapes depending on the resonance mode of free droplet, particularly in modes 2, 4, 6, and 8. In addition, the induced internal vortex flow inside the droplet was also observed in each mode. Typically, the induced flow moved upwards along the axis of symmetry and downwards along the surface of the droplet, that is, from the apex to the contact line in modes 2 and 4, after which it broke into a smaller vortex. On the other hand, the large-scale vortex always remained steady in modes 6 and 8. The speed of the flow in mode 4 was always greater than that in mode 2, but those in modes 6 and 8 were similar.
Shape Oscillation and Detachment of Droplet on Vibrating Flat Surface
Shin, Young-Sub ; Lim, Hee-Chang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 337~346
DOI : 10.3795/KSME-B.2014.38.4.337
This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately
, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.
Prediction of Thermal and Elastic Properties of Honeycomb Sandwich Plate for Analysis of Thermal Deformation
Hong, Seok Min ; Lee, Jang Il ; Byun, Jae Ki ; Choi, Young Don ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 347~355
DOI : 10.3795/KSME-B.2014.38.4.347
Thermal problems that are directly related to the lifetime of an electronic device are becoming increasingly important owing to the miniaturization of electronic devices. To solve thermal problems, it is essential to study thermal stability through thermal diffusion and insulation. A honeycomb sandwich plate has anisotropic thermal conductivity. To analyze the thermal deformation and temperature distribution of a system that employs a honeycomb sandwich plate, the thermal and elastic properties need to be determined. In this study, the thermal and elastic properties of a honeycomb sandwich plate, such as thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and shear modulus, are predicted. The properties of a honeycomb sandwich plate vary according to the hexagon size, thickness, and material properties.
Numerical Study of Electrolyte Wetting Phenomena in the Electrode of Lithium Ion Battery Using Lattice Boltzmann Method
Lee, Sang Gun ; Jeon, Dong Hyup ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 357~363
DOI : 10.3795/KSME-B.2014.38.4.357
The electrolyte wetting phenomena in the electrode of lithium ion battery is studied numerically using a multiphase lattice Boltzmann method (LBM). When a porous electrode is compressed during roll-pressing process, the porosity and thickness of the compressed electrode are changed, which can affect its wettability. In this study, the change in electrolyte distribution and degree of saturation as a result of varying the compression ratio are investigated with two-dimensional LBM approach. We found that changes in the electrolyte transport path are caused by a reduction in through-plane pore size and result in a decrease in the wettability of the compressed electrode.
CFD (Computational Fluid Dynamics) Study on Partial-Load Combustion Characteristics of a 4-Step-Grate Wood Pellet Boiler
Ahn, Joon ; Jang, Jun Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 4, 2014, Pages 365~371
DOI : 10.3795/KSME-B.2014.38.4.365
A numerical simulation was conducted for the combustion chamber of a 4-step grate-firing boiler for wood pellet fuel. The flame is extended to the exit of combustion chamber, which is reproduced by present numerical method based on a homogeneous reaction model. Flow field from the simulation shows a strong recirculation flow at the upstream corner of the chamber, along which the flame is extended to the exit. These combustion and flow characteristics remain unchanged for partial load operations, which suggest modification of the combustion chamber structure rather than resizing should be effective to improve combustion characteristics. Possible modifications for combustion chamber are suggested such as relocating its exit, increasing the number of grate steps or installing internals such as guide baffles.