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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 24, Issue 12 - Dec 2000
Volume 24, Issue 11 - Nov 2000
Volume 24, Issue 10 - Oct 2000
Volume 24, Issue 9 - Sep 2000
Volume 24, Issue 8 - Aug 2000
Volume 24, Issue 7 - Jul 2000
Volume 24, Issue 6 - Jun 2000
Volume 24, Issue 5 - May 2000
Volume 24, Issue 4 - Apr 2000
Volume 24, Issue 3 - Mar 2000
Volume 24, Issue 2 - Feb 2000
Volume 24, Issue 1 - Jan 2000
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Characteristics of the Gasoline Spray near Impinging Wall in Suction Flow
Kim, Won-Tae ; Kang, Shin-Jae ; Rho, Byung-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1285~1293
DOI : 10.22634/KSME-B.2000.24.10.1285
In port fuel injection system of SI engines, injected fuel is impinged onto the surface of intake valves and port-wall, and then formed the wall flow under the cold start operation. Wall flows entrained into the cylinder result in the unsteady and nonuniform mixture formation. Therefore, the spray impingement to the wall is considered as having negative influences such as lowering combustion efficiency and causing unburned hydrocarbon emissions. This study investigates the spray characteristics of the wall impinging air-assist spray in suction air flow. A PDPA was used to analyze the flow characteristics under the different conditions such as impingement angle and supplied air. Experimental data concerning the impinging sprays has been obtained in the vicinity of the wall. Measured droplets divided into the pre-impinging droplets which denote as the positive normal velocities and post-impinging droplets that describe as the negative normal velocities for the suction flow. Their velocities, size distributions and SMD are comparatively analyzed before and after the impingement.
The Performance Evaluation of a Gas Turbine Combustor
Ahn, Kook-Young ; Kim, Han-Seok ; Ahn, Jin-Hyuk ; Pae, Hyoung-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1294~1299
DOI : 10.22634/KSME-B.2000.24.10.1294
The combustion characteristics have been investigated to develop the 50 kW-class gas turbine combustor. The combustor design program was developed and applied to design this combustor. The combustion air which has the temperature of 45, 200,
were supplied to combustor for elucidating the effect of inlet air temperature on CO, NOx emissions and flame temperature. The exit temperature and NO were increased and CO was decreased with increasing inlet air temperature. Also, the effect of equivalence ratio was considered to verify the combustor performance. The emissions of CO and NO with inlet air temperature can be analyzed qualitatively by measuring the temperature inside the combustor. The combustion performance with fuel schedule was evaluated to get the informations of the starting and part loading process of gas turbine. The combustion was stable above the equivalence ratio of 0.18. The pattern factor which is the important parameter of combustor performance was satisfied with the design criterion. Consequently the combustor was proved to meet the performance goal required for the target gas turbine system.
Characteristics of the Droplet Behavior in the Overlap Region of Twin Spray and in Single Spray
Jung, Ji-Won ; Cha, Keun-Jong ; Kim, Duck-Jool ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1300~1308
DOI : 10.22634/KSME-B.2000.24.10.1300
The objectives of this study was to investigate the spray characteristics of single spray and twin spray in the overlap region such as mean axial velocity, mean radial velocity, mean droplet size and probability density function of droplet size. A phase doppler anemometer was used as the measurement system for droplet size and velocity. In case of single spray, injection pressure was varied from 0.2MPa to 0.7MPa. Mean axial velocity, mean radial velocity and droplet size were decreased as the distance below nozzle tip was increased. In case of twin spray, the spray characteristics were measured by varying the distance between two nozzles from 127mm to 155mm. In the overlap region, the boundary of the overlap region was determined by obtaining the distribution of mean axial and radial velocity. Droplet size was increased as the distance from nozzle tip was increased. It was found that the distribution of droplet size for twin spray in the overlap region was different to single spray.
Surface Flow Visualization of MIRA Notchback Reference Car
Chun, Chung-Hwan ; Kim, Yong-Hwan ; Cho, Kwang-Ryun ; Roh, Sang-Kil ; Lee, Eung-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1309~1316
DOI : 10.22634/KSME-B.2000.24.10.1309
A surface flow visualization of a MIRA notchback reference car was conducted using a 1/4 -scale model in the POSTECH wind tunnel. The flow separation and reattachment phenomen a around A-pillar, C-pillar, backlight, and trunk were discussed with the help of the distributions of singular points such as nodes, saddles, and spiral foci. The locations of the singular points on the trunk and the backlight from experimental results are compared with those of CFD results using the turbulence modeling of RNG k -
Fully-Implicit Decoupling Method for Incompressible Navier-Stokes Equations
Kim, Kyoung-Youn ; Baek, Seung-Jin ; Sung, Hyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1317~1325
DOI : 10.22634/KSME-B.2000.24.10.1317
A new efficient numerical method for computing three-dimensional, unsteady, incompressible flows is presented. To eliminate the restriction of CFL condition, a fully-implicit time advancement in which the Crank-Nicolson method is used for both the diffusion and convection terms, is adopted. Based on an approximate block LU decomposition method, the velocity -pressure decoupling is achieved. The additional decoupling of the intermediate velocity components in the convection term is made for the fully -implicit time advancement scheme. Since the iterative procedures for the momentum equations are not required, the velocity components decouplings bring forth the reduction of computational cost. The second-order accuracy in time of the present numerical algorithm is ascertained by computing decaying vortices. The present decoupling method is applied to minimal channel flow unit with DNS (Direct Numerical Simulation).
Experimental Study on Flow Noise Generated by Axi-symmetric Boundary Layer (II) - Forced Transition on an Axi-symmetric Nose and Radiated Sound -
Lee, Seung-Bae ; Kim, Hooi-Joong ; Kwon, O-Sup ; Lee, Sang-Kwon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1326~1334
DOI : 10.22634/KSME-B.2000.24.10.1326
The oscillatory excitation with a Strouhal number of 2.65 ncar the stagnation zone of hemispherical nose model was employed to control the laminar separation bubble and the transition to turbulence. The effects of oscillatory excitation upon the separation bubble and the transition were addressed in terms of kurtosis/skewness and time-frequency analyses. The measured noise spectrum of radiated sound from the turbulent boundary layer on the axi-symmetric infinite cylinder is compared with that by Sevik's wave-number white approximations. The noise sources in TBL on axi-symmetric cylinder and the caling of their far-field sound are also discussed.
Assessment of Numerical Optimization Algorithms in Design of Low-Noise Axial-Flow Fan
Choi, Jae-Ho ; Kim, Kwang-Yong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1335~1342
DOI : 10.22634/KSME-B.2000.24.10.1335
Three-dimensional flow analysis and numerical optimization methods are presented for the design of an axial-flow fan. Steady, incompressible, three-dimensional Reynolds-averaged Navier-Stokes equations are used as governing equations, and standard k-
turbulence model is chosen as a turbulence model. Governing equations are discretized using finite volume method. Steepest descent method, conjugate gradient method and BFGS method are compared to determine the searching directions. Golden section method and quadratic fit-sectioning method are tested for one dimensional search. Objective function is defined as a ratio of generation rate of the turbulent kinetic energy to pressure head. Two variables concerning sweep angle distribution are selected as the design variables. Performance of the final fan designed by the optimization was tested experimentally.
Characteristics of Rotor Blade Tip Vortices with Spanwise Slots
Chung, Woon-Jin ; Han, Yong-Oun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1343~1350
DOI : 10.22634/KSME-B.2000.24.10.1343
The evolutionary structure of tip vortices has been investigated with a two-dimensional LDV system for a plain and a slotted blade, respectively. To analyze the effect of slots which bypasses a part of main stream into the tip face, velocity profiles, vortex sizes, their displacements and turbulence intensities during one revolution of the rotor were measured by the phase averaging process. For the comparison of circumferential velocity components of the plain blade and the slotted blade, the peak values of the slotted blade were lower than those of the plain blade, and axial velocity components of the slotted blade were considerably larger than those of the plain blade. The slotted rotor blade enlarged the core size and made the vortex delayed compared with those of the plain blade at the same wake ages. Turbulence profiles had peaks inside the core radii and decayed gradually in the radial direction of vortex coordinate. Also, using a quasi 3-D LDV measurement technique the budget of turbulence kinetic energy was analyzed in radial direction of the vortex core.
A Numerical Analysis of Growth of Non-spherical Silica Particles in a Premixed Flat Flame
Oh, Se-Baek ; Lee, Bang-Weon ; Choi, Man-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1351~1358
DOI : 10.22634/KSME-B.2000.24.10.1351
Two dimensional aerosol dynamics considering the effects of particle generation, coagulation, thermophoresis, sintering and convection has been studied to obtain the growth of non-spherical silica particles in conjunction with determining flame temperature by performing combustion analysis of premixed flat flame. Heat and mass transfer analysis includes 16 species, 29 chemical reaction steps together with oxidation and hydrolysis of SiCl4. The effect of radiation heat loss has also been included. The predictions of flame temperatures and the evolution of particle size distributions were in a reasonable agreement with the existing experimental data.
Investigation of the Performance Characteristics of an In-Situ Particle Monitor at Low Pressures Using Aerodynamic Lenses
Bae, Gwi-Nam ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1359~1367
DOI : 10.22634/KSME-B.2000.24.10.1359
In-situ particle monitors(ISPMs) are widely used for monitoring contaminant particles in vacuum-based semiconductor manufacturing equipment. In the present research, the performance of a Particle Measuring Systems(PMS) Vaculaz-2 ISPM at low pressures has been studied. We generated the uniform sized methylene blue particle beams using three identical aerodynamic lenses in the center of the vacuum line, and measured the detection efficiency of the ISPM. The effects of particle size, particle concentration, mass flow rate, system pressure, and arrangement of aerodynamic lenses on the detection efficiency of the ISPM were examined. Results show that the detection efficiency of the ISPM greatly depends on the mass flow rate, and the particle Stokes number. We also found that the optimum Stokes number ranges from 0.4 to 1.9 for the experimental conditions.
Numerical Study on Pulverized Coal Combustion Applying Two-Phase WSGGM
Yu, Myoung-Jong ; Kang, Shin-Jae ; Baek, Seung-Wook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1368~1379
DOI : 10.22634/KSME-B.2000.24.10.1368
A numerical study on swirling pulverized coal combustion in an axisymmetric enclosure is carried out by applying the 2-phase weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard and RNG k-
turbulence model, whereas the Lagrangian approach is used for the particulate phase. The eddy-dissipation model is employed for the reaction rate for gaseous mixture, and the single-step and two-step first-order reaction model for the devolatilization process for coal. Special attention is given to establish the thermal boundary conditions on radiative transfer equation By comparing the numerical results with experimental ones, the radiation model used here is confirmed and found to provide an alternative for simulating the radiative transfer.
Comparative Analysis of Models for Free Convective Film Condensation on an Isothermal Vertical Wall
Sung, Hyun-Chan ; Kim, Kyoung-Hoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1380~1387
DOI : 10.22634/KSME-B.2000.24.10.1380
The existing theoretical models for steady two-dimensional free convective laminar film condensation of pure saturated or superheated vapor under atmospheric pressure on isothermal vertical wall have been reviewed. To investigate the effects such as inertia, thermal convective and liquid-vapor interface shear stress, the models of constant or variable properties in liquid film for condensation of saturated vapor are compared in detail with Nusselt model. Also, for condensation of superheated vapor, the effects of superheated temperature and variable properties in liquid and vapor layers are examined and then a new correlation is proposed to predict the heat transfer. The results are in good agreement with the Shang's correlation within 2% errors.
A Study on the Measurement Uncertainty of Pipe Prover
Lim, Ki-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1388~1398
DOI : 10.22634/KSME-B.2000.24.10.1388
A pipe prover is a flowmeter calibrator used in flow measurement field. Gravimetric and volumetric methods were applied to determine the basic volume of the pipe prover. Uncertainty of its basic volume measurement was evaluated in accordance with the procedure recommended by International Organization for Standardization. The combined standard uncertainty of determining the basic volume was estimated from the sensitivity coefficient and the standard uncertainty of independent variables. It was found that the uncertainties of the weighing and volume measurements have dominant influence on that of the basic volume determination. With the quantitative analysis of the sensitivity coefficient, the contribution of the each variable uncertainty to the combined standard uncertainty of the basic volume is shown clearly.
Temperature Field Measurement of Non-Isothermal Jet Flow Using LIF Technique
Yoon, Jong-Hwan ; Lee, Sang-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1399~1408
DOI : 10.22634/KSME-B.2000.24.10.1399
A 2-dimensional temperature field measurement technique using PLIF (Planar Laser Induced Fluorescence) was developed and it was applied to an axisymmetric buoyant jet. Rhodamine B was used as a fluorescent dye. Laser light sheet illuminated a two-dimensional cross section of the jet. The intensity variations of LIF signal from Rhodamine B molecules scattered by the laser light were captured with an optical filter and a CCD camera. The spatial variations of temperature field of buoyant jet were derived using the calibration data between the LIF signal and real temperature. The measured results show that the turbulent jet is more efficient in mixing compared to the transition and laminar jet flows. As the initial flow condition varies from laminar to turbulent flow, the entrainment from ambient fluid increases and temperature decay along the jet center axis becomes larger. In addition to the mean temperature field, the spatial distributions of temperature fluctuations were measured by the PLIF technique and the result shows the shear layer development from the jet nozzle exit.
Large-Eddy Simulation of Turbulent Flows in a Planar Combustor
Kim, Do-Hyeong ; Yang, Kyung-Soo ; Shin, Dong-Shin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 10, 2000, Pages 1409~1416
DOI : 10.22634/KSME-B.2000.24.10.1409
In this study, turbulent flows in a planar combustor which has a square rib-type flame holder are numerically investigated by Large Eddy Simulation(LES). Firstly, the flow fields with or without jet injection downstream of the flame-holder are examined using uniform inlet velocity. Comparison of the present LES results with experimental one shows a good agreement. Secondly, to investigate mixing of oxidizer(air) and fuel injected behind the flame holder, the scalar-transport equation is introduced and solved. From the instantaneous flow and scalar fields, complex and intense mixing phenomena between fuel and jet are observed. It is shown that the ratio of jet to blocked air velocity is an important factor to determine the flow structure. Especially, when the ratio is large enough, the fuel jet penetrates the main vortices shed from the flame holder, resulting in significant changes in the flow and scalar fields.