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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 40, Issue 9 - Sep 2016
Volume 40, Issue 8 - Aug 2016
Volume 40, Issue 7 - Jul 2016
Volume 40, Issue 6 - Jun 2016
Volume 40, Issue 5 - May 2016
Volume 40, Issue 4 - Apr 2016
Volume 40, Issue 3 - Mar 2016
Volume 40, Issue 2 - Feb 2016
Volume 40, Issue 1 - Jan 2016
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Effects of Port Shape on Steady Flow Characteristics in an SI Engine with Semi-Wedge Combustion Chamber (1) - Velocity Distribution (1)
Kim, Hyeongsig ; Ohm, Inyong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 417~427
DOI : 10.3795/KSME-B.2016.40.7.417
This paper is the first investigation of the steady flow characteristics of an SI engine with a semi-wedge combustion chamber as a function of the port shape. For this purpose, the planar velocity profiles were measured at the 1.75B position by particle image velocimetry. The flow patterns were examined with both a straight and a helical port. Two swirls were observed up to 4 mm valve lift with the straight port and up to 2 mm with the helical one; however, only one swirl was present after these lifts. The flow characteristics changed suddenly between 4 and 5 mm lift in the straight port; on the other hand, the change with lift was gradual with the helical port - the transition points between flow regimes were different with the port shapes. In addition, the centers of the swirls were relatively far from the cylinder center so that the effect of eccentricity may not be negligible at 1.75B, regardless the shape. The eccentricity values with the straight port were especially high - over 0.5 for all lifts. Finally, real velocities were found to be much lower than those predicted by the assumption of ISM evaluation, with the profiles differing qualitatively as well.
Numerical Study on Urea Spraying and Mixing Characteristics with Application of Static Mixer in Marine SCR System
Jang, Jaehwan ; Park, Hyunchul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 429~434
DOI : 10.3795/KSME-B.2016.40.7.429
Among various De-NOx technologies, Urea-based Selective Catalytic Reduction (SCR) systems are known to be the most effective in marine diesel applications. The spraying and mixing behavior of the urea-water solution has a decisive effect on the system's net efficiency. Therefore, in this study, the spray behavior and ammonia uniformity with and without a static mixer were analyzed by CFD in order to optimize the SCR system. The results showed that the static mixer significantly affected the uniformity of velocity and ammonia concentration. Static mixers may be especially suited for marine SCR systems with space constraints.
Effects of the Temporal Increase Rate of Reynolds Number on Turbulent Channel Flows
Jung, Seo Yoon ; Kim, Kyoungyoun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 435~440
DOI : 10.3795/KSME-B.2016.40.7.435
Effects of the increase rate of Reynold number on near-wall turbulent structures are investigated by performing direct numerical simulations of transient turbulent channel flows. The simulations were started with the fully-developed turbulent channel flow at
, then temporal accelerations were applied. During the acceleration, the Reynolds number, based on the channel width and the bulk mean velocity, increased almost linearly from 5600 to 13600. To elucidate the effects of flow acceleration rates on near-wall turbulence, a wide range of durations for acceleration were selected. Various turbulent statistics and instantaneous flow fields revealed that the rapid increase of flow rate invoked bypass-transition like phenomena in the transient flow. By contrast, the flow evolved progressively and the bypass transition did not clearly occur during mild flow acceleration. The present study suggests that the transition to the new turbulent regime in transient channel flow is mainly affected by the flow acceleration rate, not by the ratio of the final and initial Reynolds numbers.
Numerical Technique to Analyze the Flow Characteristics of a Propeller Using Immersed Boundary Lattice Boltzmann Method
Kim, Hyung Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 441~448
DOI : 10.3795/KSME-B.2016.40.7.441
The thrust force created by a propeller depends on the incoming flow velocity and the rotational velocity of the propeller. The performance of the propeller can be described by dimensionless variables, advanced ratio, thrust coefficient, and power coefficient. This study included the application of the immersed boundary lattice Boltzmann method (IBLBM) with the stereo lithography (STL) file of the rotating object for performance analysis. The immersed boundary method included the addition of the external force term to the LB equation defined by the velocity difference between the lattice points of the propeller and the grid points in the domain. The flow by rotating a 4-blade propeller was simulated with various Reynolds numbers (Re) (including 100, 500 and 1000), with advanced ratios in the range of 0.2~1.4 to verify the suggested method. The typical tendency of the thrust efficiency of the propeller was obtained from the simulation results of different advanced ratios. It was also necessary to keep the maximum mesh size ratio of the propeller surface to a grid size below 3. Additionally, a sufficient length of the downstream region in the domain was maintained to ensure the numerical stability of the higher Re and advanced ratio flow.
Fog Collection/Removal System Using a Moss Filter
Oh, Sunjong ; Park, Minyong ; Kim, Wandoo ; Lim, Hyuneui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 449~455
DOI : 10.3795/KSME-B.2016.40.7.449
Fog causes economic losses in transportation. It also results in health problems when it is combined with air pollutants. Considerable research efforts have focused on developing fog removal systems. However, most systems operate themselves after monitoring the fog. Additionally, continuous energy supply and maintenance are required to retain the fog-removal efficiency of the system. This study included the demonstration of a moss filter (a polyolefin mesh interlaced with moss) as a fog-removal method overcoming the limitations of the fog removal system. Three types of mosses with different surface structures were investigated to elucidate the relation between the moisture absorption rate and the structures. Among the different moss types, Hypopterygium japinicum showed the highest efficiency based on the smallest pore diameter and the largest total pore area. The visibilities with the moss filter and the polyolefin mesh were compared to perform the fog removal tests. The moss filter could provide a cost-effective and eco-friendly fog removal system with sustainability.
Numerical Study of Low-pressure Subcooled Flow Boiling in Vertical Channels Using the Heat Partitioning Model
Lee, Ba-Ro ; Lee, Yeon-Gun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 457~470
DOI : 10.3795/KSME-B.2016.40.7.457
Most CFD codes, that mainly adopt the heat partitioning model as the wall boiling model, have shown low accuracies in predicting the two-phase flow parameters of subcooled boiling phenomena under low pressure conditions. In this study, a number of subcooled boiling experiments in vertical channels were analyzed using a thermal-hydraulic component code, CUPID. The prediction of the void fraction distribution using the CUPID code agreed well with experimental data at high-pressure conditions; whereas at low-pressure conditions, the predicted void fraction deviated considerably from measured ones. Sensitivity tests were performed on the submodels for major parameters in the heat partitioning model to find the optimized sets of empirical correlations suitable for low-pressure subcooled flow boiling. The effect of the K-factor on the void fraction distribution was also evaluated.
Temperature Evaluation on Long-term Storage of Radioactive Waste Produced in the Process of Isotope Production
Jeong, Namgyun ; Jo, Daeseong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 471~475
DOI : 10.3795/KSME-B.2016.40.7.471
In the present study, temperature evaluations on long-term storage of radioactive waste produced in the process of isotope production were performed using two different methods. Three-dimensional analysis was carried out assuming a volumetric heat source, while two-dimensional studies were performed assuming a point source. The maximum temperature difference between the predictions of the volumetric and point source models was approximately
. For the conceptual design level, a point source model may be suitable to obtain the overall temperature characteristics of different loading locations. For more detailed analysis, the model with the volumetric source may be applicable to optimize the loading pattern in order to obtain minimum temperatures.
One-dimensional Numerical Analysis of the Effect of Seawater Feed Rate on Multi-effect Solar Stills
Lim, Byung-Ju ; Yu, Sang-Seok ; Park, Change-Dae ; Chung, Kyung-Yul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 7, 2016, Pages 477~484
DOI : 10.3795/KSME-B.2016.40.7.477
In a multi-effect solar distiller, a feeding rate of seawater to each effect should be decreased as the effect number is increased. In previous studies, the feed rate of seawater was not reduced evenly between the effects, which is unreasonable, since the thermal energy input of each effect decreases by the same amount. In this work, numerical analysis was carried out in order to elucidate this discrepancy. The results showed that the amount of distillates produced was almost the same for both evenly and unevenly reduced flow rates between the effects. Optimum feed rates of seawater with various energy inputs from exhaust gas heat exchanger were also obtained. The results showed that the optimum feed rate of the first effect increased linearly or reached a steady state depending on the heat flux.