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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 29, Issue 12 - Dec 2005
Volume 29, Issue 11 - Nov 2005
Volume 29, Issue 10 - Oct 2005
Volume 29, Issue 9 - Sep 2005
Volume 29, Issue 8 - Aug 2005
Volume 29, Issue 7 - Jul 2005
Volume 29, Issue 6 - Jun 2005
Volume 29, Issue 5 - May 2005
Volume 29, Issue 4 - Apr 2005
Volume 29, Issue 3 - Mar 2005
Volume 29, Issue 2 - Feb 2005
Volume 29, Issue 1 - Jan 2005
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A Numerical Study on the Heat Transfer Characteristics of Impinging Jet Flow in the Presence of Applied Magnetic Fields
Lee Hyun Goo ; Yoon Hyun Sik ; Hong Seung Do ; Ha Man Yeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 653~661
DOI : 10.3795/KSME-B.2005.29.6.653
The present study numerically investigates two-dimensional fluid flow and heat transfer ir the confined jet flow in the presence of applied magnetic field. For the purpose of controlling vortex shedding and heat transfer, numerical simulations to calculate the fluid flow and heat transfer in the confined jet are performed for different Reynolds numbers in the absence and presence of magnetic fields and for different Prandtl numbers of 0.02 (liquid metal), 0.7 (air) and 7 (water) in the range of
, where N is the Stuart number (interaction parameter) which is the ratio of electromagnetic force to inertia force. The present study reports the detailed information of flow and thermal quantities in the channel at different Stuart numbers. As the intensity of applied magnetic fields increases, the vortex shedding formed in the channel becomes weaker and the oscillating amplitude of impinging jet decreases. The flow and thermal fields become the steady state if the Stuart number is greater than the critical value. Thus the Nusselt number at the stagnation point representing the heat transfer characteristics also vary as a function of Stuart number.
Study on Combustion Performance and Burning Velocity in a Micro Combustor
Na Hanbee ; Lee Dae Hoon ; Kwon Sejin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 662~670
DOI : 10.3795/KSME-B.2005.29.6.662
The effect of heat loss on combustion performance and burning velocity of micro combustors in various conditions were exploited experimentally. Three different gases were used, and various geometric matrixes were considered to figure out the phenomena of combustion in a micro combustor. The micro combustors used in this study were constant volume combustors and had cylindrical shape. Geometric parameter of combustor was defined as combustor height and diameter. The effect of height was exploited parametrically as 1mm, 2mm and 3 mm and the effect of diameter was parameterized to be 7.5 mm and 15 mm. Three different combustibles which were Stoichiometric mixtures of methane and air, hydrogen and air, and mixture of hydrogen and air with fuel stoichiometry of two were used. By pressure measurement and visualization of flame propagation, characteristic of flame propagation was obtained. Flame propagations which were synchronized with pressure change within combustor were analyzed. From the analysis of images obtained during the flame propagations, burning velocity at each location of flame was obtained. About
decrease in burning velocity of
stoichiometric mixture compared with previous a empirical result was observed, and we can conclude that it is acceptable to use empirical equations for laminar premixed flame burning velocity to micro combustions. Results presented in this paper will give fine tool for analysis and prediction of combustion process within micro combustors.
Numerical Signal Prediction and Calibration Using the Theory of a Current-Type Electromagnetic Flowmeter for Two-Phase Slug Flow
Ahn Yeh-Chan ; Oh Byung Do ; Kim Jong-Rok ; Kim Moo Hwan ; Kang Deok-Hong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 671~686
DOI : 10.3795/KSME-B.2005.29.6.671
The transient nature and complex geometries of two-phase gas-liquid flows cause fundamental difficulties when measuring flow velocity using an electromagnetic flowmeter. Recently, a current-sensing flowmeter was introduced to obtain measurements with high temporal resolution (Ahn et al.). In this study, current-sensing flowmeter theory was applied to measure the fast velocity transients in slug flows. The velocity fields of axisymmetric gas-liquid slug flow in a vertical pipe were obtained using Volume-of-Fluid (VOF) method, and the virtual potential distributions for the electrodes of finite size were also computed using the finite volume method for simulating slug flow. The output signal prediction for slug flow was carried out from the velocity and virtual potential (or weight function) fields. The flowmeter was numerically calibrated to obtain the cross-sectional liquid mean velocity at an electrode plane from the predicted output signal. Two calibration parameters are proposed for this procedure: a flow pattern coefficient and a localization parameter. The flow pattern coefficient was defined by the ratio of the liquid resistance between the electrodes for two-phase flow with respect to that for single-phase flow, and the localization parameter was introduced to avoid errors in the flowmeter readings caused by liquid acceleration or deceleration around the electrodes. These parameters were also calculated from the computed velocity and virtual potential fields. The results can be used to obtain the liquid mean velocity from the slug flow signal measured by a current-sensing flowmeter.
Tensorial Time Scales for Turbulent Gradient Transport of Reynolds Stresses
Cho Choong Won ; Kim Kyoungyoun ; Sung Hyung Jin ; Chung Myung Kyoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 687~695
DOI : 10.3795/KSME-B.2005.29.6.687
On the notion that the Reynolds stresses are transported with different time scale depending on the transport direction, the third order velocity correlations are represented by a new turbulent gradient transport model with tonsorial Lagrangian time scale. In order to verify the proposed model, DNS data are first obtained in a turbulent channel flow at Re = 180 and tonsorial Lagrangian time scales are computed. The present model predictions are compared with DNS data and those predicted by the third-order turbulent transport model of Hanjalic and Launder that uses a scalar time scale. The result demonstrates that the Reynolds stresses are indeed transported with different time scale depending on the transport direction.
Effect of Incidence Angle on the Endwall Heat Transfer Within a Turbine Rotor Passage
Park Jin Jae ; Lee Sang Woo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 696~702
DOI : 10.3795/KSME-B.2005.29.6.696
The effect of incidence angle on the endwall heat (mass) transfer characteristics within a turbine rotor cascade passage has been investigated by employing the naphthalene sublimation technique. The experiments are carried out at the Reynolds number of
for two incidence angles of -5 and 5 dog. The result shows that the incidence angle has a considerable influence on the transport phenomena over the endwall. The positive incidence angle tends to promote development of the pressure-side leg of a leading-edge horseshoe vortex. The endwall thermal load is augmented by 7.5 percents at i = -5 deg but is reduced by 2.5 percents at i = 5 deg, in comparison with that at the design condition.
Study on the Finite Element Discretization of the Level Set Redistancing Algorithm
Kang Sungwoo ; Yoo Jung Yul ; Lee Yoon Pyo ; Choi HyoungGwon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 703~710
DOI : 10.3795/KSME-B.2005.29.6.703
A finite element discretization of the advection and redistancing equations of level set method has been studied. It has been shown that Galerkin spatial discretization combined with Crank-Nicolson temporal discretization of the advection equation of level set yields a good result and that consistent streamline upwind Petrov-Galerkin(CSUPG) discretization of the redistancing equation gives satisfactory solutions for two test problems while the solutions of streamline upwind Petrov-Galerkin(SUPG) discretization are dissipated by the numerical diffusion added for the stability of a hyperbolic system. Furthermore, it has been found that the solutions obtained by CSUPG method are comparable to those by second order ENO method.
An Experimental Study of Smoke Movement in Tunnel Fire with Natural and Forced Ventilations
Hwang Cheol-Hong ; Yoo Byung-Hun ; Kum Sung-Min ; Kim Jung-Yup ; Shin Hyun-Joon ; Lee Chang-Eon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 711~721
DOI : 10.3795/KSME-B.2005.29.6.711
In order to design of emergency ventilation systems, the smoke movements in tunnel fire with natural and forced ventilation were investigated. Reduced-scale experiments were carried out under the Froude scaling with novel fire source consisting many wicks. Temperature profiles were measured under the ceiling and vertical direction along the center of the tunnel and poisonous gases were measured at emergency exit point in the natural ventilation case. In forced ventilation, temperature profiles were measured with various flow rate to obtain critical velocity. The results showed that the interval of emergency exit having 225m was estimated reasonably through the measurements of temperature variation and poisonous gas in the natural ventilation. In the case of forced ventilation, the temperature distribution near fire source is remarkably different from that of natural ventilation. Also, the critical velocity to prevent upstream smoke flow has the range of 0.57m/s between 0.64m/s. Finally, it was also identified that although the increase of flow rate can suppress the backward flow of smoke to upstream direction, brings about the increase of flame intensity near stoichiometric fuel/air ratio.
Comparative Performance Analysis of Pressurized Solid Oxide Fuel Cell / Gas Turbine Hybrid Systems Considering Different Cell Inlet Preheating Methods
Yang Won Jun ; Kim Jae Hwan ; Kim Tong Seop ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 722~729
DOI : 10.3795/KSME-B.2005.29.6.722
Design analysis of the solid oxide fuel cell and gas turbine combined power system is performed considering different methods for preheating cell inlet air. The purpose of air preheating is to keep the temperature difference between cell inlet and outlet within a practical design range thus to reduce thermal stress inside the cell. Three different methods considered are (1) adopting a burner in front of the cell, (2) adopting a preheater (heat transfer from the main combustor) in front of the cell and (3) using recirculation of the cathode exit gas. For each configuration, analyses are carried out for two values of allowable maximum cell temperature difference. Performance characteristics of all cases are compared and design limitations are discussed. Relaxation of the cell temperature difference (larger difference) is proved to ensure higher efficiency. Recirculation of the cathode exit gas exhibits better performance than other methods and this advantage becomes more prominent as the constraint of the cell temperature difference becomes more severe (smaller temperature difference).
Effect of Flame Interaction on the NO Emission
Kim Jin Hyun ; Lee Byeong-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 730~736
DOI : 10.3795/KSME-B.2005.29.6.730
It has been reported that the interacting multiple jet flames of propane fuel are not extinguished even at the choking velocity at the nozzle exit if eight small nozzles are arranged along the imaginary circle of
times the diameter of single nozzle. In this research, experiments were conducted to know the NO and CO emission characteristics of the interacting flames. Measurements along the centerline of the flame revealed that decrease in CO concentration was followed by the NO decrease and
increase. It was found that interacting flame emitted less NO than that of similar area single jet flame. Also, NO emission of partially premixed interacting flame was decreased up to
of that of non-premixed multiple jet flame. Though the mechanism of the NO reduction was not clear from this experiment, it's been shown that partially premixed multiple jet flames could be used to achieve clean and highly stable combustion.
Effects of Rotation Speed on Heat Transfer and Flow in a Coolant Passage with Turning Region ( I ) - Cross Ribbed Duct -
Kim Kyung Min ; Kim Yun Young ; Rhee Dong Ho ; Cho Hyung Hee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 737~746
DOI : 10.3795/KSME-B.2005.29.6.737
The present study investigates heat/mass transfer and flow characteristics in a ribbed rotating passage with turning region. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter (
) of 26.67 mm. Rib turbulators are attached in the cross arrangement on the leading and trailing surfaces of the passage. The ribs have a rectangular cross section of
and an attack angle of
. The pitch-to-rib height ratio (p/e) is 7.5, and the rib height-to-hydraulic diameter ratio (
) is 0.075. The rotation number ranges from 0.0 to 0.20 while the Reynolds number is constant at 10,000. To verify the heat/mass transfer augmentation, internal flow structures are calculated for the same conditions using a commercial code FLUENT 6.1. The heat transfer data of the smooth duct for various Ro numbers agree well with not only the McAdams correlation but also the previous studies. The cross-rib turbulators significantly enhance heat/mass transfer in the passage by disturbing the main flow near the surfaces and generating one asymmetric cell of secondary flow skewing along the ribs. Because the secondary flow is induced in the first-pass and turning region, heat/mass transfer discrepancy is observed in the second-pass even for the stationary case. When the passage rotates, heat/mass transfer and flow phenomena change. Especially, the effect of rotation is more dominant than the effect of the ribs at the higher rotation number in the upstream of the second-pass.
Study on the Pressure Drop Characteristics of Liquid Flow in Open Microchannels with the Countercurrent Vapor Flow
Kim Sung Jin ; Nam Myeong Ryong ; Seo Joung Ki ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 747~754
DOI : 10.3795/KSME-B.2005.29.6.747
Because the liquid-vapor interfacial shear stress affects seriously the liquid flow and the maximum heat transport rate of the grooved wick heat pipe, an accurate modeling for the pressure drop characteristics of the liquid flow is required. A novel method for calculating the liquid pressure drop and the velocity profile of an open channel flow in a microchannel with an arbitrary cross-section is suggested and validated by experiments. An experimental apparatus for the Poiseuille number of the liquid flow in open rectangular microchannels with the hydraulic diameters of 0.40mm, 0.43mm, 0.48mm is used in order to reproduce real situations in the grooved wick heat pipe. Analytic results from the suggested method are compared with the experimental data and they are in a close agreement with each other.
Static Wind Tunnel Test of Smart Un-manned Aerial Vehicle(SUAV) for TR-S2 Configuration
Choi Sungwook ; Cho Taehwan ; Chung Jindeog ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 755~762
DOI : 10.3795/KSME-B.2005.29.6.755
To evaluate the aerodynamic efficiency of TR-S2 configuration designed by SUDC, wind tunnel tests of
scaled model were done in KARI LSWT. The aerodynamic characteristics of plain and Semi-Slotted Flaperon were compared, and vortex generators were installed to improve flow pattern along the wing surface. Effects of the control surface such as elevator, rudder, aileron, and incidence angle of horizontal tail are measured for various testing conditions. Test results showed that Semi-Slotted Flaperon produced more favorable lift, lift/drag, and stall margins and application of vortex generator would be best choice to enhance wing performance. Longitudinal, lateral and directional characteristics of TR-S2 were found to be stable for the pitch and yaw motions.
A Study on the Performance of a Domestic Small Multi Refrigerator According to a Capillary Tube Change
Kim Sang Uk ; Lee Moo Yeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 29, issue 6, 2005, Pages 763~771
DOI : 10.3795/KSME-B.2005.29.6.763
This paper is an experimental study on the performance according to a capillary tube diameter and length in a domestic small multi refrigerator[kimchi refrigerator]. Pressure drop in a capillary tube is predicted by theoretical analysis and experimental method as the reduction of capillary tube diameter from 0.74 to 0.6 mm. The differences between experimental results and analytical results are mainly caused by friction factor in a capillary tube. Because there are no adequate equations used to calculate pressure drop of capillary tube diameter under 1.0mm. The empirical equations necessary for interpretation of capillary tube were derived from capillary tube test results data using curve fitting method. This study shows that the optimized designs of system, which is capillary tube length and refrigerant charge amount, are 2000mm, 83g at the capillary tube diameter 0.6mm and 3000mm, 73g at the capillary tube diameter 0.74mm. And capillary design tools and system matching techniques necessary for development of the kimchi refrigerator were also developed through this study.