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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 28, Issue 12 - Dec 2004
Volume 28, Issue 11 - Nov 2004
Volume 28, Issue 10 - Oct 2004
Volume 28, Issue 9 - Sep 2004
Volume 28, Issue 8 - Aug 2004
Volume 28, Issue 7 - Jul 2004
Volume 28, Issue 6 - Jun 2004
Volume 28, Issue 5 - May 2004
Volume 28, Issue 4 - Apr 2004
Volume 28, Issue 3 - Mar 2004
Volume 28, Issue 2 - Feb 2004
Volume 28, Issue 1 - Jan 2004
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Experimental Study on the Three Dimensional Unsteady Flow in a Counter-Rotating Axial Flow Fan
Park, Hyun-Soo ; Cho, Lee-Sang ; Cho, Jin-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1005~1014
DOI : 10.3795/KSME-B.2004.28.9.1005
Experiments were done for the three dimensional unsteady flow in a counter-rotating axial flow fan under peak efficiency operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the 45
inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. It has been found that the radial and tangential velocity components disappeared, while the axial velocity component highly increased as soon as the tip vortex was generated. It has been observed that secondary flow and turbulence intensity which were increased by the front rotor were dissipated passing through the rear rotor. As the result the energy loss of the counter rotating axial flow fan decreased at the downstream of rear rotor. Also, it has been verified that tip vortex pattern of the rear rotor was dampened because the tip vortex generated by front rotor was mixed with that of the rear rotor.
Analysis of Flow in a Microchannel Branch by Using Micro-PIV Method
Yoon, Sang-Youl ; Kim, Kyung-Chun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1015~1021
DOI : 10.3795/KSME-B.2004.28.9.1015
Micro-resolution Particle Image Velocimetry(Micro-PIV) was used to measure the flow in a micro-branch(Micro-Bypass). In this paper, effects of particle lump at the tip of a Micro-branch and difficulties of Micro-PIV measurements for microfluidics with branch passage were described. Micro-bypass was composed of a straight channel(200(100)
m height) and two branches which has 100(50)
m height. One of branches was straight and the other was curved. Experiments were performed at three regions along streamwise direction(entrance, middle and exit of branch) and five planes along vertical direction (0,
m) for the range of Re
Large Eddy Simulation of Turbulent Channel Flow Using Inhomogeneous Filter
Lee, Sang-Hwan ; Kim, Kwang-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1022~1031
DOI : 10.3795/KSME-B.2004.28.9.1022
The commutation errors by the filtering process in the large eddy simulation are considered. It is compared the conventional filter with the inhomogeneous filter that is devised to reduce the commutation errors. The weighting factor of the inhomogeneous filter suggested by Vasilyev is adopted. Also, using the optimizing function that estimates test filter width to eliminate the dissipations in the region excluding the vicinity of the wall, the flow patterns are analyzed. It is evaluated in simulations of the turbulent channel flow at Reynolds number of 1020, based on friction velocity and channel half height. Results show that the commutation errors can be significantly reduced by using the inhomogeneous filter and the optimized test filter width.
Coherent Structure Extraction from 3-Dimensional Isotropic Turbulence Velocity Field Using Discrete Wavelet Transform
Lee, Sang-Hwan ; Jung, Jae-Yoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1032~1041
DOI : 10.3795/KSME-B.2004.28.9.1032
In this study we decompose the 3-dimensional velocity field of isotropic turbulent flow into the coherent and the incoherent structure using the discrete wavelet. It is shown that the coherent structure, 3% wavelet modes, has 98% energy and 88% enstrophy and its statistical characteristics are almost same as the original turbulence structure. And it is confirmed that the role of the coherent structure is that it produces the turbulent kinetic energy at the inertia range then transfers energy to the dissipation range. The incoherent structure, with residual wavelet modes, is uncorrelated and has the Gaussian probability density function but it dissipates the kinetic energy in dissipation range. On the procedure, we propose a new but easy way to get the threshold by applying the energy partition percentage concept about coherent structure. The vorticity field extracted from the wavelet-decomposed velocity field has the same structure as the result of the precedent studies which decomposed vorticity field directly using wavelet. Therefore it has been shown that velocity and vorticity field are on the interactive condition.
Theoretical Study on the Characteristics of Pressure Change of High Speed Train in Tunnels
Nam, Seong-Won ; Kwon, Hyeok-Bin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1042~1050
DOI : 10.3795/KSME-B.2004.28.9.1042
Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The severe pressure change in tunnel may give rise to the ear-discomfort for passenger and fatigue for car body. The external and internal pressure of rolling stock have been measured by using the running test with atmospheric pressure sensors and portable data acquisition system in high speed train. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. We found that there are similar patterns of external pressure change for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity. And, the patterns of pressure wave in tunnel are classified into eight groups.
Shape Design of Heat Transfer Surfaces with Angled Ribs Using Numerical Optimization Techniques
Kim, Hong-Min ; Kim, Kwang-Yong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1051~1057
DOI : 10.3795/KSME-B.2004.28.9.1051
A numerical optimization procedure for the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer is presented. The response surface method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analyses of flow and heat transfer. SST turbulence model is used as a turbulence closure. Computational results for local heat transfer rate show reasonable agreements with experimental data. The pitch-to-height ratio of the rib and rib height-to-channel height ratio are set to be 9.0 and 0.1, respectively, and width-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. Full-factorial experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained in the range from 0.0 to 0.1 of weighting factor.
A Study on the Axial Velocity Profile of Developing Laminar Flows in a Straight Duct Connected to a Square Curved Duct
Sohn, Hyun-Chull ; Lee, Haeng-Nam ; Park, Gil-Moon ; Lee, Hong-Gu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1058~1065
DOI : 10.3795/KSME-B.2004.28.9.1058
In the present study, characteristics of steady state laminar flows of a straight duct connected to a 180
curved duct were examined in the entrance region through experimental and numerical analyses. For the analysis, the governing equations of laminar flows in the Cartesian coordinate system were applied. Flow characteristics such as velocity profiles, and secondary flows were investigated numerically and experimentally in a square cross-sectional straight duct by the PIV system and a CFD code(STAR CD). For the PIV measurement, working fluid produced from mosquito coils smoke. The experimental data were obtained at 9 points dividing the test sections by 400 mm. Experimental and numerical results can be summarized as follows. Critical Reynolds number, Recr which indicates transition from laminar steady flow to transition steady flow was 2,150. As Reynolds number, Re, was increased, dimensionless velocity profiles at the outer wall were increased due to the effect of the centrifugal force and the secondary flows. The intensity of a secondary flow became stronger at the inner wall rather than the outer wall regardless of Reynolds number.
Design and Performance Evaluation of a Diode Type Corona Charger for Real-Time Measurement of the Submicron Aerosol
Cho, Myung-Hoon ; Ji, Jun-Ho ; Park, Dong-Ho ; Bae, Gwi-Nam ; Hwang, Jung-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1066~1074
DOI : 10.3795/KSME-B.2004.28.9.1066
With a diode corona charger, which is a component of ELPI(Electrical Low Pressure Impactor), aerosol particles are charged to make electrical detection possible before they are collected by the impactor. We designed and evaluated two cylindrical corona chargers, each of which had a central corona needle electrode. For the performance evaluation of each corona charger the polydisperse dioctyl sebacate(DOS) particles, with diameters of 0.1∼0.8
m and NaCl particles, smaller than 0.1
m, were used. The particles were then led through an electrostatic classifier (TSI model 3081) to classify monodisperse aerosol with minimal size deviation. After evaluating the wall loss of the particles in the corona charger, we measured the product of penetration and number of charges, Pㆍn, to evaluate the corona charger efficiency at high positive voltages of 4, 5, 6 kV.
Engine Performance and Emissions Characteristics in an LPG Engine Converted with Mixer and LPi System Fuel Supply Methods
Choi, Gyeung-Ho ; Kim, Jin-Ho ; Cho, Ung-Lae ; Han, Sung-Bin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1075~1080
DOI : 10.3795/KSME-B.2004.28.9.1075
In this study, performance and emissions characteristics of an liquefied petroleum gas (LPG) engine converted from a diesel engine were examined by using mixer system and liquid propane injection (LPi) system fuel supply methods. A compression ratio for the base diesel engine, 21, was modified into 8, 8.5, 9 and 9.5. The cylinder head and the piston crown were modified to roe the LPG in the engine. Ignition timing was controlled to be at minimum spark advance for best torque (MBT) each case. Engine performance and emissions characteristics are analyzed by investigating engine power, brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), volumetric efficiency, CO, THC and NOx. Experimental results showed that the LPi system generates higher power and lower emissions than the conventional mixer fuel supply method.
Synthesis of Multi-Walled Carbon Nanotubes and Nanofibers on a Catalytic Metal Substrate Using an Ethylene Inverse Diffusion Flame as a Heat Source
Lee, Gyo-Woo ; Jurng, Jong-Soo ; Kang, Kyung-Tae ; Hwang, Jung-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1081~1092
DOI : 10.3795/KSME-B.2004.28.9.1081
The synthesis of Ni-catalyzed multi-walled carbon nanotubes and nanofibers on a catalytic metal substrate, using an ethylene fueled inverse diffusion flame as a heat source, was investigated. When the gas temperature was varied from 1,400K to 900K, approximately, carbon nanotubes with diameters of 20∼60nm were formed on the substrate. In the regions where the gas temperature was higher than 1,400K or lower than 900K, iron nanorods or carbon nanofibers were synthesized, respectively. Based on the quantitative analyses of large amount of SEM and TEM images, the nanotubes formed closer to the flame had a tendency of having larger diameters. HR-TEM images and Raman spectra revealed that carbon nanotubes synthesized had multi-walled structures with some defective graphite layers at the wall. Based on the graphite mode of the Raman spectra, it was believed that the optimal synthesis could be obtained as the substrate was positioned at between 5.5mm and 5.0mm, from the flame axis.
Numerical Study of Heat Transfer Associated with Droplet Impact
Kim, Sung-Il ; Son, Gi-Hun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1093~1100
DOI : 10.3795/KSME-B.2004.28.9.1093
Numerical analysis of the heat transfer associated with droplet impact on a hot solid surface is performed by solving the equations governing conservation of mass, momentum and energy in the liquid and gas phases. The deformed droplet shape is tracked by a level set method which is modified to achieve volume conservation and to include the effect of contact angle at the wall. The numerical method is validated through the calculations for the cases reported in the literature. Based on the numerical results, the heat transfer rate is found to depend strongly on the droplet spread radius. Decreased advancing/receding contact angles enlarge the splat radius and in turn enhance the wall heat flux. The effect of impact velocity on the droplet spread is reduced as the droplet size decreases. Also, droplet atomization is observed to significantly enhance the heat transfer rate and the effect is pronounced for a smaller size of droplet. An existing model equation to predict the maximum spread radius is improved for application to a micro droplet.
Nano-Soot Particle Formation in Ethene/Air Inverse Diffusion Flame
Lee, Eui-Ju ; Shin, Hyun-Joon ; Oh, Kwang-Chul ; Shin, Hyun-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1101~1109
DOI : 10.3795/KSME-B.2004.28.9.1101
Experimental measurements of flame structure and soot characteristics were performed fur ethene inverse diffusion flames (IDF). IDF has been considered as the excellent flow field to study the incipient soot because soot particle do not experience the oxidation process. In this study, LIF image clarified the reaction zone of IDF with OH signal and PAH distribution. laser light scattering technique also identified the being of soot particle. To address the degree of soot maturing, C/H ratio and morphology of soot sample were investigated. From these measurements, the effect of flow residence time and temperature on soot inception could be suggested, and more details on soot characteristic in the IDF was determined according to fuel dilution and flame condition. The fuel dilution results in a decrease of temperature and enhancement of residence time, but the critical dilution mole fraction is existed for temperature not to effect on soot growth. Also, the soot inception evolved on the specific temperature and its morphology are independent of the fuel dilution ratio of fuel.
Measurement of Soot Nano-Particle Using LIIM(Laser-Induced Ion Mobility)
Lee, Eui-Ju ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1110~1116
DOI : 10.3795/KSME-B.2004.28.9.1110
Experimental measurements of laser-induced ion mobility(LIIM) were performed for ethene/air premixed flames operated near the soot inception point. Soot was ionized using a pulsed laser operated at 532 nm. The ionization signal was collected with a tungsten electrode located in the post-flame region. ionization signals were collected using both a single electrode and dual electrode configuration. Prior LIIM studies have focused on the use of a single biased electrode to generate the electric field, with the burner head serving as the path to ground. In many practical combustion systems, a path to ground is not readily available. To apply the LIIM diagnostic to these geometries, a dual electrode geometry must be employed. The influence of electrode configuration, flame equivalence ratio, and flame height on ionization signal detection was determined. The efficacy of the LIIM diagnostic to detect soot inception in the post-flame region of a premixed flame using a dual electrode configuration was investigated. For the different dual electrode configurations tested, the dual parallel electrode geometry was observed to be most sensitive to detect the soot inception point in a premixed flame.
WSR Study of Particle Size, Concentration and Chemistry Near Soot Inception
Lee, Eui-Ju ; Mulholland, George W. ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1117~1123
DOI : 10.3795/KSME-B.2004.28.9.1117
The characteristics of soot near the soot inception point for an ethene-air flame was carried out in a WSR (well-stirred reactor). The new sampling tool like the temperature controlled filter system was introduced to minimize the condensation during sampling. The new analysis tools applied include the real time size distribution analysis with the Nano-DMA, particle size by transmission electron microscopy, C/H analysis, g filter analysis, and thermogravimetric analysis using both non-oxidative and oxidative pyrolysis. The WSR can generate young soot particles that can be collected and examined to gain insight into inception. For the current conditions, soot does not form for
Inverse Problem of Determining Unknown Inlet Temperature Profile in Two Phase Laminar Flow in a Parallel Plate Duct by Using Regularization Method
Hong, Yun-Ky ; Baek, Seung-Wook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1124~1132
DOI : 10.3795/KSME-B.2004.28.9.1124
The inverse problem of determining unknown inlet temperature in thermally developing, hydrodynamically developed two phase laminar flow in a parallel plate duct is considered. The inlet temperature profile is determined by measuring temperature in the flow field. No prior information is needed for the functional form of the inlet temperature profile. The inverse convection problem is solved by minimizing the objective function with regularization method. The conjugate gradient method as iterative method and the Tikhonov regularization method are employed. The effects of the functional form of inlet temperature, the number of measurement points and the measurement errors are investigated. The accuracy and efficiency of these two methods are compared and discussed.
About the Shape Optimization of Ex-Manifold Diffuser
Jo, Sok-Hyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 9, 2004, Pages 1133~1138
DOI : 10.3795/KSME-B.2004.28.9.1133
Shape optimization method was coupled with a conventional CFD analysis to find the optimal shape of ex-manifold diffuser which decreases the maldistribution of flow above the catalyst. Shape optimization results show that flow uniformity above the catalyst was increased about 28% fur the axi-symmetric case and about 18% for the asymmetric case. The axi-symmetric type can be applied to the diffuser of under floor catalyst and the asymmetric type can be applied to the diffuser of close coupled catalyst.