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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 27, Issue 12 - Dec 2003
Volume 27, Issue 11 - Nov 2003
Volume 27, Issue 10 - Oct 2003
Volume 27, Issue 9 - Sep 2003
Volume 27, Issue 8 - Aug 2003
Volume 27, Issue 7 - Jul 2003
Volume 27, Issue 6 - Jun 2003
Volume 27, Issue 5 - May 2003
Volume 27, Issue 4 - Apr 2003
Volume 27, Issue 3 - Mar 2003
Volume 27, Issue 2 - Feb 2003
Volume 27, Issue 1 - Jan 2003
Selecting the target year
Through Flow Analysis and Leakage Flow of a Regenerative Pump
Sim, Chang-Yeul ; Kang, Shin-Hyoung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1015~1022
DOI : 10.3795/KSME-B.2003.27.8.1015
Flows in a regenerative pump were calculated for several flow-rates, using the CFX-Tascflow. The calculated results show the vortex structure in the impeller and side channel. The predicted performance shows considerable discrepancy from the measured values for low flow rates. Main source of the difference is the leakage flow of pump strongly affecting the performance of pump. A simple correlation was proposed using calculated leakage flows through the simplified passage. One dimensional analysis were made for the recirculating flow and angular momentum transfer using calculated three dimensional data base.
Double Frequency Forcing of the Laminar Separated Flow over a Backward-Facing Step
Kim, Sung-Wook ; Choi, Hae-Cheon ; Yoo, Jung-Yul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1023~1032
DOI : 10.3795/KSME-B.2003.27.8.1023
The effect of local forcing on the separated flow over a backward-facing step is investigated through hot-wire measurements and flow visualization with multi-smoke wires. The boundary layer upstream of the separation point is laminar and the Reynolds number based on the free stream velocity and the step height is 13800. The local forcing is given from a slit located at the step edge and the forcing signal is always defined when the wind tunnel is in operation. In case of single frequency forcing, the streamwise velocity and the reattachment length are measured under forcing with various forcing frequencies. For the range of 0.010〈S
〈0.013, the forcing frequency component of the streamwise velocity fluctuation grows exponentially and is saturated at x/h
A Study on Two-Phase Flow Pattern of Pure Refrigerants R134a and Rl23 and Zeotropic Mixture R134a/R123 in Horizontal Tubular
Lim, Tae-Woo ; Kim, Jun-Hyo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1033~1041
DOI : 10.3795/KSME-B.2003.27.8.1033
Two-phase flow pattern data during horizontal in-tube flow boiling are presented for pure and mixed refrigerants of R134a and Rl23, The flow pattern is observed through tubular sight glasses located at inlet and outlet of the test section, which is made of a stainless steel tube, 2m long with 10mm I.D., 1.5mm wall thickness. The obtained results are compared with the available various correlations for flow pattern. The flow pattern map of Hashizume was in good agreement with the present data except the region of low mass velocity. Weisman flow pattern map was also known to satisfactorily predict data for refrigerants in the region of annular flow. In this study, the flow pattern are simply classified into two groups; stratified(including intermittent, stratified and stratified-wavy) flow and annular flow. The transition quality from stratified to annular flow was obtained by modifying the liquid Froude number.
Optimal Flow Control of Ceiling Type Indoor Unit by PIV Measurements
Sung, Jae-Yong ; An, Kwang-Hyup ; Lee, Gi-Seop ; Choi, Ho-Seon ; Lee, In-Seop ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1042~1050
DOI : 10.3795/KSME-B.2003.27.8.1042
A heating flow discharged from a 4-way ceiling type indoor unit has been investigated to determine the design parameters for the optimal flow control. The flow was measured by a PIV(particle image velocimetry) system and an experimental model of 1/10 scale with a transparent room was devised by satisfying the Archimedes number. This similarity is generally used in cases where the forced convection has similar magnitude of the natural convection. To optimize the heating flow, several vane angles and vane control algorithms of cross and right angle controls were considered. Regarding the vane angle, experimental results show that 30
is an optimal angle to avoid re-suction flows without significant increase in flow noise. Temperature distribution measured in the environmental chamber ensures the increased thermal comfort when compared to the case, 60
angle. At the optimal angle, applying open/close control gives rise to more uniform distribution of the heating flow than without control. Especially, the cross-control seems to be satisfactory for thermal comfort.
Experimental Study on the Characteristics of Heat and Mass Transfer on the Teflon Coated Tubes
Lee, Jang-Ho ; Kim, Hyeong-Dae ; Kim, Jung-Bae ; Kim, Moo-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1051~1060
DOI : 10.3795/KSME-B.2003.27.8.1051
The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm ; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate.
An Experimental Study on the Effects of Concentration Gradient and Mean Velocity on the Liftoff Characteristics of the Triple Flame
Seo, Jeong-Il ; Kim, Nam-Il ; Oh, Kwang-Chul ; Shin, Hyun-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1061~1070
DOI : 10.3795/KSME-B.2003.27.8.1061
A triple flame in a mixing layer was studied experimentally with concentration gradient and mean velocity by using a multi-slot burner, which can stabilize the lift-off flame. Flame stabilization condition, lift-off heights, and some other characteristics were examined for methane and propane flame within a range of very low concentration gradient. Pitot-tube and LDV(Laser Doppler Velocimetry) were used for velocity. Mass spectroscopy and Rayleigh scattering signal were used for concentration gradients. Thermo-couples and SiC TFP(Thin Filament Pyrometer) were used for temperature. It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity and this means that the propagation velocity has a maximum value. The scales of flame to the burner nozzle and intensity variation of the diffusion flame were suspected as the cause.
A Study on the Development and the Uncertainty Analysis of Oil Flow Standard System
Lim, Ki-Won ; Choi, Jong-Oh ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1071~1080
DOI : 10.3795/KSME-B.2003.27.8.1071
A national standard system was developed in order to calibrate and test the oil flowmeters for the petroleum field. A stop valve and a gyroscopic weighing scale were employed for the primary standard of the flow quantity. It is operated by the standing start and finish mode and the static weighing method. The model equation for uncertainty evaluation was based on the calibration principle of standard system. The sources of the uncertainties were quantified and combined according to the GUM(Guide to the Expression of Uncertainty in Measurement). It was found that the standard system had the relative expanded uncertainty of 0.04 % in the range of 18 - 350 ㎥/ｈ. According to the uncertainty budget, the uncertainties of the fluid density and the volume of pipeline, which were temperature dependent, contributed 92% of final uncertainty in the oil flow standard system.
On the Structures of Taylor Vortices.
Hwang, Jong-Yeon ; Yang, Kyung-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1081~1088
DOI : 10.3795/KSME-B.2003.27.8.1081
Numerical investigation on the structures of various Taylor vortices induced in the flow between two concentric cylinders, with the inner one rotating and with a pressure-driven axial flow imposed, is carried out, and compared with the experiments of Wereley and Lueptow [Phys. fluid, 11(12), 1999] who studied the Taylor vortices using PIV in detail. Especially, the properties of helical vortices and random wavy vortices are discussed, and their three-dimensional structures are visualized using the numerical data. Our simulation also predicts that random wavy vortices have quasi-periodic movement which can be explained by traveling waves formed in the azimuthal direction. The numerical results are well consistent with the experimental findings of Wereley and Lueptow.
Blow-off and Combustion Characteristics of a Lifted Coaxial Diffusion Flame
Kwark, Ji-Hyun ; Jun, Chung-Hwan ; Jang, Young-June ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1089~1096
DOI : 10.3795/KSME-B.2003.27.8.1089
An experiment was performed to investigate lift-off, blow-off and combustion characteristics of a lifted coaxial diffusion flame according to fuel jet and air velocity. A jet diffusion flame which is attached on the nozzle rim begins to be lifted with increase of air velocity, and finally becomes blow-off at higher air velocity. In experiment, blow-off limit increased with increase of fuel jet velocity, however lift-off occurred at lower air velocity. Flame structure and combustion characteristics were examined by schlieren photos, temperature distributions and emission concentration distributions. Flame temperature became higher at midstream and its RMS became larger at up and downstream with increase of air velocity. Local NO concentration decreased but
concentration increased with increase of air velocity, which shows combustion reaction becomes close to be stoichiometric at higher air velocity in spite of lift-off.
Predictions of Microscale Separated Flow using Langmuir Slip Boundary Condition
Lee, Do-Hyung ; Meang, Joo-Sung ; Choi, Hyung-Il ; Na, Wook-Sang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1097~1104
DOI : 10.3795/KSME-B.2003.27.8.1097
The current study analyzes Langmuir slip boundary condition theoretically and it is tested in practical numerical analysis for separation-associated flow. Slip phenomenon at the channel wall is properly implemented by various numerical slip boundary conditions including Langmuir slip model. Compressible backward-facing step flow is compared to other analysis results with the purpose of diatomic gas Langmuir slip model validation. The numerical solutions of pressure and velocity distributions where separation occurs are in good agreement with other numerical results. Numerical analysis is conducted for Reynolds number from 10 to 60 for a prediction of separation at T-shaped micro manifold. Reattachment length of flows shows nonlinear distribution at the wall of side branch. The Langmuir slip model predicts fairly the physics in terms of slip effect and separation.
Analysis of a Vortex Structure Near the Strip Edge for Preventing Edge Zn Overcoation
Cho, Choong-Won ; Kim, Sang-Joon ; Ahn, Gi-Jang ; Chung, Myung-Kyoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1105~1113
DOI : 10.3795/KSME-B.2003.27.8.1105
In the gas wiping process of continuous hot-dip galvanizing, edge overcoating develops near the edge of the steel strip. The overcoating is supposed to occur due to the reduced impact pressure of wiping gas on the strip surface. The purpose of this study is to investigate the effect of edge vortex on the reduced impact pressure. Three-dimensional unsteady flows are simulated using a commercial code, STAR-CD. Standard k-
model is used as a turbulence model. It is found that an alternating vortex structure in the vicinity of strip edge is developed by buckling of opposed jet streams and that the reduced amount of impact pressure at strip edge becomes smaller as the air knife gets closer to the strip. The effect of edge baffle on the reduced impact pressure is also investigated.
Frost Formation in a Straight Duct under Turbulent Flow
Yang, Dong-Keun ; Lee, Kwan-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1114~1121
DOI : 10.3795/KSME-B.2003.27.8.1114
A mathematical model considering the air side and the frost layer is presented to predict the frost layer growth. The standard k-
model for the air flow and the diffusion and energy equations for the frost layer are employed. The numerical results are compared with experimental data to validate the present model, and agree well with experimental data within a maximum error of 10%. The present model predicts well the frost properties and heat and mass transfer with respect to the frosting time. The variation of total heat transfer strongly depends on the operating condition, and has a similar trend to that of the sensible heat transfer. The frost properties along the flow direction are also investigated.
Numerical Characteristics of Upwind Schemes for Preconditioned Navier-Stokes Equations
Gill, Jae-Heung ; Lee, Du-Hwan ; Sohn, Duk-Young ; Choi, Yun-Ho ; Kwon, Jang-Hyuk ; Lee, Seung-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1122~1133
DOI : 10.3795/KSME-B.2003.27.8.1122
Numerical characteristics of implicit upwind schemes, such as upwind ADI, line Gauss-Seidel (LGS) and point Gauss-Seidel (LU) algorithms, for Navier-Stokes equations have been investigated. Time-derivative preconditioning method was applied for efficient convergence at low Mach/Reynolds number regime as well as at large grid aspect ratios. All the algorithms were expressed in approximate factorization form and von Neumann stability analysis was performed to identify stability characteristics of the above algorithms in the presence of high grid aspect ratios. Stability analysis showed that for high aspect ratio computations, the ADI and LGS algorithms showed efficient damping effect up to moderate aspect ratio if we adopt viscous preconditioning based on min-CFL/max-VNN time-step definition. The LU algorithm, on the other hand, showed serious deterioration in stability characteristics as the grid aspect ratio increases. Computations for several practical applications also verified these results.
Combustion Analysis with CARS Temperature Measurement in a Gas Turbine Combustor
Lee, Jong-Ho ; Park, Chul-Woong ; Han, Yeoung-Min ; Ko, Young-Sung ; Lee, Su-Yong ; Yang, Soo-Seok ; Lee, Dae-Sung ; Jeon, Chung-Hwan ; Chang, Young-June ; Shin, Hyun-Dong ; Hahn, Jae-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1134~1141
DOI : 10.3795/KSME-B.2003.27.8.1134
Performance of a gas turbine combustor installed in a test facility has been studied by measuring spatially- and temporally-resolved temperature distributions using multiplex CARS technique. 500 CARS temperatures were determined at each measuring point to obtain a histogram of temperature distribution. Experiments were carried out in the aero-engine combustor sector rig burning standard kerosene fuel. The histograms were obtained around a triple-sector double annular rig running in ground idle conditions, showing features of flow mixing within the rig. The temperature histograms that prove the existence of high temperatures above 1900 K provide us valuable information to improve the design of the combustor structure suppressing NOx generation in turbulent combustion processes. The effects of swirl direction and pre-filmer on gas turbine combustion were investigated. When we installed radial swirls, a large recirculation zone was formed by the fuel module regardless of swirl directions and the pre-filmer installation. It is found that the swirl direction affects the shape of the reverse flow zone, however. Also, an attempt to estimate the flow field and flame structure is made using the histogram of temperature determined with the CARS technique.
Computational Fluid Dynamics Study on Two-Dimensional Sloshing in Rectangular Tank
Kwack, Young-Kyun ; Ko, Sung-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1142~1149
DOI : 10.3795/KSME-B.2003.27.8.1142
The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank moving in harmonic or pitching motion. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the location of the free-surface filling any some fraction of cells with fluid. The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height, horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Damping effects by baffles were extensively investigated for various conditions in terms of baffle shape and position.
Evaluation of Nonlinear κ-ε Models on Prediction Performance of Turbulence-Driven Secondary Flows
Myong, Hyon-Kook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1150~1157
DOI : 10.3795/KSME-B.2003.27.8.1150
Nonlinear relationship between Reynolds stresses and the rate of strain of nonlinear k-
models is evaluated theoretically by using the boundary layer assumptions against the turbulence-driven secondary flows in noncircular ducts and then their prediction performance is validated numerically through the application to the fully developed turbulent flow in a square duct. Typical predicted quantities such as mean axial and secondary velocities, turbulent kinetic energy and Reynolds stresses are compared with available experimental data. The nonlinear k-
model adopted in a commercial code is found to be unable to predict accurately duct flows with the prediction level of secondary flows one order less than that of the experiment.
Nonlinear Acoustic-Pressure Responses of H
/Air Counterflow Diffusion Flames
Kim, Hong-Jip ; Chung, Suk-Ho ; Sohn, Chae-Hoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1158~1164
DOI : 10.3795/KSME-B.2003.27.8.1158
Steady-state structure and acoustic-pressure responses of
/Air counterflow diffusion flames are studied numerically with a detailed chemistry in view of acoustic instability. The Rayleigh criterion is adopted to judge acoustic amplification or attenuation from flame responses. Steady-state flame structures are first investigated and flame responses to various acoustic-pressure oscillations are numerically calculated in near-equilibrium and near-extinction regimes. The acoustic responses of
/Air flame show that the responses in near-extinction regime always contribute to acoustic amplification regardless of acoustic-oscillation frequency Flames near extinction condition are sensitive to pressure perturbation and thereby peculiar nonlinear responses occur, which could be a possible mechanism in generating the threshold phenomena observed in combustion chamber of propulsion systems.
Impact of Phonon Dispersion on Thermal Conductivity Model
Chung, Jae-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1165~1173
DOI : 10.3795/KSME-B.2003.27.8.1165
The effects of (1) phonon dispersion on thermal conductivity model and (2) differentiation of group velocity and phase velocity are examined for germanium. The results show drastic change of thermal conductivity regardless of the same relaxation time model. Also the contribution of transverse acoustic (TA) phonon and longitudinal acoustic (LA) phonon on the thermal conductivity at high temperatures is reassessed by considering more rigorous dispersion model. Holland model, which is commonly used for modeling thermal conductivity, underestimates the scattering rate for TA phonon at high frequency. This leads the conclusion that TA is dominant heat transfer mode at high temperatures. But according to the rigorous consideration of phonon dispersion, the reduction of thermal conductivity is much larger than the estimation of Holland model, thus the TA at high frequency is expected to be no more dominant heat transfer mode. Another heat transfer mechanism may exist at high temperatures. Two possible explanations we the roles of (1) Umklapp scattering of LA phonon at high frequency and (2) optical phonon.
Drag Reduction of a Circular Cylinder With O-rings
Lim, Hee-Chang ; Lee, Sang-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1174~1181
DOI : 10.3795/KSME-B.2003.27.8.1174
The flow around a circular cylinder was controlled by attaching O-rings to reduce drag force acting on the cylinder. Four experimental models were tested in this study; one smooth cylinder of diameter D (D
Numerical Study on the Drag of a Car Model under Road Condition
Kim, Beom-Jun ; Kang, Sung-Woo ; Choi, Hyoung-gwon ; Yoo, Jung-Yul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1182~1190
DOI : 10.3795/KSME-B.2003.27.8.1182
A parallelized FEM code based on domain decomposition method has been recently developed for large-scale computational fluid dynamics. A 4-step splitting finite element algorithm is adopted for unsteady flow computation of the incompressible Navier-Stokes equation, and Smagorinsky LES model is chosen for turbulent flow computation. Both METIS and MPI Libraries are used for domain partitioning and data communication between processors, respectively. Tiburon model of Hyundai Motor Company is chosen as the computational model at Re
An Elementary Study on the Combustion Mechanism of Levitated Droplet Clusters by Ultrasonic Wave
Jung, Jin-Do ; Kim, Seung-Mo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 8, 2003, Pages 1191~1199
DOI : 10.3795/KSME-B.2003.27.8.1191
This paper describes to observe the combustion process of only one droplet cluster. In this study, liquid fuel was atomized by ultrasonic wave to form an acoustically levitated droplet cluster. In order to elucidate the detailed structure of burning process of the droplet cluster, laser tomography method was applied. Time-series planar images of fuel droplets were processed and diameter of the each droplet was calculated based on the Mie-scattering theory. Using these data, the modified droplet group combustion number was estimated in time-series. As the result, when the internal droplet group combustion occur, the modified group combustion number dose not decrease monotonically, but show a tow-staged decreasing process. In all case of combustion process, combustion reactions were measured two types that combustion speed was fast and slow. It was casued by difference of concentration degree and droplet size distribution.