Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Transactions of the Korean Society of Mechanical Engineers B
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
Editor in Chief :
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
Selecting the target year
A Research on the PIV Algorithm Using Image Coding
Kim, Sung-Kyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 153~160
DOI : 10.22634/KSME-B.2000.24.2.153
A Particle Image Velocimetry(PIV) algorithm is developed to analyze whole flow field both qualitatively and quantitatively. The practical use of PIV requires the use of fast, reliable, computer-based methods for tracking numerous particles suspended in a flow field. The TSS, NTSS, FFT-Hybrid, which are developed in the area of image compression and coding, are introduced to develop fast vector search algorithm. The numerical solution of the lid-driven cavity flow by the ADI algorithm with the Wachspress Formula is introduced to produce synthetic data for the validation of the tracking algorithms. The algorithms are applied to image data of real flow experiments. The comparisons in CPU time and mean error show, with a small loss of accuracy, CPU time for tracking is reduced considerably.
Lean Combustion Characteristics in a S.I Engine with SCV by Operating Conditions
Choi, Su-Jin ; Jeon, Chung-Hwan ; Chang, Young-June ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 161~168
DOI : 10.22634/KSME-B.2000.24.2.161
Lean combustion in a SI engine is one of the best solution for the improvement of fuel economy and reduction of pollutant emission. In order to access a lean combustion engine, stable combustion at lean AlF ratio is needed. In this paper, the effect of fuel injection timing on lean misfire limit has been investigated in an MPI engine. To investigate the interaction of injection timing and intake flow characteristics, three different swirl generating SCV(swirl control valve) configurations were considered, and investigated their effects on lean misfire limit and torque at full load operation. Also the effects of spark timing on lean combustion has been investigated. Lean combustion has been examined and the results are reported in this paper. SCV B has been developed to satisfy the requirements of sufficient swirl generation to improve lean combustion and stable performance. It is found that injection timing, spark timing and intake air motion govern the stable lean combustion.
Free Convective Transition of Intermediate Prandtl-Number Fluids in a Wide-Gap Horizontal Annulus
Yoo, Joo-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 169~176
DOI : 10.22634/KSME-B.2000.24.2.169
Natural convection in a wide-gap horizontal annulus is considered, and the transition of flows and the bifurcation phenomenon are investigated for the fluids with Pr=0.2 and 0.3. At Pr=0.2, a bicellular flow pattern is observed at high Rayleigh number, and the solution is unique. At Pr=0.3, both the steady unicellular and bicellular flows exist above a certain critical Rayleigh number. For the fluids of Pr=0.2, the bicellular flow can be obtained by the impulsive heating of the inner cylinder, but it is not obtained from the zero initial condition for Pr=0.3. Hysteresis phenomena have not been observed. A transition from a bicellular flow to a unicellular flow occurs for Pr=0.3.
Measurements of Temperature Field and Film-Cooling Effectiveness for a Shower-Head Film Cooling
Jeong, Chul-Hee ; Lee, Sang-Woo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 177~187
DOI : 10.22634/KSME-B.2000.24.2.177
Measurements of temperature fields and film-cooling effectiveness have been conducted for a shower-head film cooling on the leading edge of a blunt body, which simulates a first-stage turbine stator. In this study, three injection cases are employed for an average blowing ratio based on freestream velocity, M, of 0.5, 1.0 and 1.5. Two (Case 1), four (Case 2) and six (Case 3) rows of normal holes are symmetrically drilled on the three tested circular-cylinder leading edges. The measurements show that regardless of M, the film-cooling effectiveness increases as the injection row is situated at farther downstream location. In Case 1, the film-cooling effectiveness is highest for M = 0.5 and lowest for M = 1.5. On the contrary, in Case 3, the film-cooling effectiveness is highest for M = 1.0 and lowest for M = 0.5. When M = 0.5, the film coverage by the first row of the injection holes deteriorates as the number of the injection row increases. In particular, the film-cooling effectiveness due to the injection through the first row of the holes in Case 3, has a nearly zero value.
Improvement of Calibration Method of Thermochromic Liquid Crystal Reflecting Measurement Angle
Yoon, Soon-Hyun ; Sim, Jae-Kyung ; Woo, Chang-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 188~194
DOI : 10.22634/KSME-B.2000.24.2.188
Thermochromic liquid crystal reflect a unique color at even temperature. Therefore, they have been successfully applied to non-intrusive heat transfer research. Hue capturing method is widely used in the quantitative measurement from the TLC image. However it is affected by several measurement conditions. The distances of camera and light source have little influence on the color, but the value of hue is seriously affected by the measurement angle. In this study, the hue capturing method is improved by considering the effect of measurement angle. This improved calibration method can diminish the misreading of temperature caused by curvature of test surface.
Effect of Arrays of Impinging Jets with Crossflow on Heat/Mass Transfer
Yoon, Pil-Hyun ; Rhee, Dong-Ho ; Cho, Hyung-Hee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 195~203
DOI : 10.22634/KSME-B.2000.24.2.195
The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Fluid from the spent jets is constrained to flow out of the system in one direction. Therefore, the spent fluid makes a crossflow in the confined space. The present study investigates effects of jet-orifice-plate to impingement-surface spacing and jet Reynolds number. The spanwise- and overall-averaged heat/mass transfer coefficients are obtained by numerical integrating the local heat transfer coefficients. The local maximum heat/mass transfer coefficients move further in the downstream direction due to the increase of crossflow velocity. At the mid-way between adjacent jets, the heat/mass transfer coefficients have a small peak owing to the collision of the adjacent wall jets and are affected strongly by the crossflow. The effect of the crossflow occurs strongly at the small orifice-to-impingement surface distance.
Numerical Simulation of Flow and Heat Transfer Characteristics of Impinging Jet Using
Choi, Bum-Ho ; Lee, Jung-Hee ; Choi, Young-Ki ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 204~213
DOI : 10.22634/KSME-B.2000.24.2.204
This study deals with jet impingement, which is extensively used in the process industries to achieve intense heating, cooling or drying rates and also widely employed as a test flow for turbulent models due to its complex flow configuration, on a flat plate by numerical methods. In this calculation, the finite volume method was employed to solve the Navier-stokes equation based on the non-orthogonal coordinate with non-staggered variable arrangement. To get a better understanding for the fluid flow and heat transfer characteristics of the turbulent jet impingements,
turbulent model was adapted and compared with the experimental data and the result of standard
turbulent model. Numerical calculations were carried out with various flow rates, nozzle to plate distances. In the case of the axisymmetric jet impingement on a flat plate,
turbulent model showed better agreement with the experimental data than the standard
turbulent model in the prediction of the mean velocity profiles, the turbulent velocity profiles. the turbulent shear stress and the heat transfer rate. The highest heat transfer rate can be obtained when the impingement occurs within the potential core..
Interferometric Measurements of the Thickness Distribution of the Liquid Sheet Formed by Two Impinging Jets
Choo, Yeon-Jun ; Kang, Bo-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 214~223
DOI : 10.22634/KSME-B.2000.24.2.214
In this research, a study on the characteristics of the liquid sheet formed by two impinging jets is presented. Using the interference phenomena of light, the thickness of the liquid sheet, which seems to heavily affect the size of the droplets, is measured and compared with existing theoretical modelings. Thinner liquid sheet is produced with larger impinging angle, smaller orifice diameter, and higher azimuthal angle but the jet velocity doesn't affect the thickness. More viscous liquid produces thicker liquid sheet. The theoretical modelings predict the same trend as the experiments but the thickness values are overestimated at low azimuthal angles. This difference is gradually decreased as the azimuthal angle is increased: The breakup mechanism of the droplets from the liquid sheet is visualized by a high speed camera. The crest around the edge of the liquid sheet is protruded with the accumulation of liquid at the end of protuberance, which contracts into a spherical shape and then becomes detached when the stem breaks down, producing large droplets with a few small size of satellites.
Numerical Analyses on Wall-Attaching Offset Jet with Various Turbulent
Models and Skew-Upwind Scheme
Seo, Ho-Taek ; Boo, Jung-Sook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 224~232
DOI : 10.22634/KSME-B.2000.24.2.224
models (i.e., standard model, modified models with streamline curvature modification and/or preferential dissipation modification) are applied in order to analyze the turbulent flow of wall-attaching offset jet. For numerical convergence, this paper develops a method of slowly increasing the convective effect induced by skew-velocity in skew-upwind scheme (hereafter called Partial Skewupwind Scheme). Even though the method was simple, it was efficient in view of convergent speed, computer memory storage, programming, etc. The numerical results of all models show good prediction in first order calculations (i.e., reattachment length, mean velocity, pressure), while they show some deviations in ·second order (i.e., kinetic energy and its dissipation rate). Like the previous results obtained by upwind scheme, the streamline curvature modification results in better prediction, while the preferential dissipation modification does not.
Condensation Heat Transfer for Pure HFC Refrigerants and a Ternary Refrigerant Mixture Inside a Horizontal Tube
Oh, Jong-Taek ; Hihara, Eiji ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 233~240
DOI : 10.22634/KSME-B.2000.24.2.233
An experimental study of condensation heat transfer was performed for pure refrigerants HFC32, HFCI25, and HFC134a, and a ternary refrigerant mixture of HFC32/125/134a (23/25/52wt%). The heat transfer coefficients were measured inside a horizontal smooth tube 5.8 mm I.D. and 8.0 m long. The refrigerant temperature at inlet was 40
, and the mass flux was varied from 150 to 400
. As for the pure refrigerants, the heat transfer coefficient of HFC32/125/l34a decreased as the quality decreased. In addition, the heat transfer coefficient of HFC32/l25/134a was about 20 % lower than HFC 134a at a low mass flux but showed no reduction at a high mass flux. The heat transfer coefficient of ternary refrigerant mixtures was 30% lower on the average than that of the pure refrigerant.
R-22 Condensation in Flat Aluminum Multi-Channel Tubes
Kim, Jung-Oh ; Cho, Jin-Pyo ; Kim, Nae-Hyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 241~250
DOI : 10.22634/KSME-B.2000.24.2.241
In this study, condensation heat transfer tests were conducted in flat aluminum multi-channel tubes using R-22. Two internal geometries were tested ; one with smooth inner surface and the other with micro-fins. Data are presented for the followin~ range of variables ; vapor quality(
), mass flux(
) and heat flux(
). The micro-fin tube showed higher heat transfer coefficients compared with those of the smooth tube. The difference increased as the vapor quality increased. Surface tension force acting on the micro-fin surface at the high vapor quality is believed to be responsible. Different from the trends of the smooth tube, where the heat transfer coefficient increased as the mass flux increased, the heat transfer coefficient of the micro-fin tube was independent of the mass flux at high vapor quality, which implies that the surface tension effect on the fin overwhelms the vapor shear effect at the high vapor quality. Present data(except those at low mass flux and high quality) were well correlated by equivalent Reynolds number, Existing correlations overpredicted the present data at high mass flux.
Effect of Secondary Flows on the Particle Collection Efficiency in Single Stage Electrostatic Precipitator
Lee, Jae-Bok ; Bae, Gwi-Nam ; Hwang, Jung-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 251~259
DOI : 10.22634/KSME-B.2000.24.2.251
The ionic wind formed in a nonuniform electric field has been recognized to have a significant effect on particle collection in an electrostatic precipitator(ESP). Under normal operating conditions the effect of ionic wind is not pronounced. However, as the flow velocity becomes smaller, the ionic wind becomes pronounced and induces secondary flow, which has a significant influence on the flow field and the particle collecting efficiency. In this paper, experiments for investigating the effect of secondary flow on collection efficiencies were carried out by changing the flow velocities in 0.2-0.7m/s and the applied voltages in 9-11kV/cm. The particle size distributions and concentrations are measured by DMA and CNC. To analyze the experimental results, numerical analysis of electric filed in ESP was carried out. It shows that particle collection is influenced by two independent dimensionless numbers,
, decreases for constant
, the secondary flow prohibits the particle collection. But when
increases for constant
, it enhances the particle collection by driving the particles into the collection region.
Three-Dimensional Flow Characteristics in the Downstream Region of a Butterfly-Type Valve Used in Air-Conditioning Systems
Park, Sang-Won ; Lee, Sang-Woo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 260~269
DOI : 10.22634/KSME-B.2000.24.2.260
Oil-film flow visualizations and three-dimensional flow measurements have been conducted in the downstream region of a butterfly-type valve used in air-conditioning systems, with the variation of a disk open angle. The flow visualizations in the flow symmetry plane show that there are a pair of counter-rotating separation/recirculation zones as wall as two jet-like near-wall flows. These flow disturbances are strongly depends on the disk open angle. Based on the flow visualization, a qualitative flow model is suggested in the near-field and downstream region of the valve disk. For a small disk open angle, the mean velocities and turbulent intensities have relatively small values in the near-field of the valve disk, but they do not show uniform distributions even in some downstream region. With an increment of the disk open angle, mean velocity variations and turbulent intensities are greatly increased in the immediate downstream region, but uniform distributions are quickly resumed as departing from the valve disk. The mass flow rate remains nearly constant for the disk open angles less than 30 degrees, meanwhile it strongly depends on the disk open angles between 45 and 75 degrees. The pressure loss is found to be about zero for the disk open angles less than 45 degrees, but is substantially increased for those larger than 75 degrees.
A Numerical Study for Optimum Configuration of Pulverized Coal Nozzle to Prevent Uneven Distribution of Particle
Kim, Hyuk-Je ; Song, Si-Hong ; Park, Seok-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 270~279
DOI : 10.22634/KSME-B.2000.24.2.270
Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutants emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle configuration. Basically, nozzle which has mixed flow of gas and particle is required to have the balanced coal concentration at exit, but it is very difficult to obtain that by itself without help of other device. In this study, coal distribution and pressure drop in gas-solid flow are calculated by numerical method in nozzle with various shapes of venturi diffuser as a means to get even coal particle distribution. The tentative correlations of pressure drop and exit coal distribution are deduced as function of the height, length and reducing angle of venturi from the calculated results. When coal hurner nozzle is designed, these equations are very useful to optimize the shape of venturi which minimize uneven particle distribution and pressure drop within coal nozzle.
Cross-Spectral Characteristics of Wall Pressure Fluctuations in Flows over a Backward-Facing Step
Lee, In-Won ; Sung, Hyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 280~287
DOI : 10.22634/KSME-B.2000.24.2.280
Laboratory measurements were made of wall pressure fluctuations in a separated and reattaching flow over a backward-facing step. An array of 32 microphones along the streamwise direction was utilized. Various statistical properties of pressure fluctuations were scrutinized. The main emphasis was placed on the flow inhomogeneity along the streamwise direction. One point statistics such as the streamwise distribution of rms pressure and autospectra were shown to be generally consistent with other studies. The coherences and wavenumber spectra in the streamwise directions were indicative of the presence of dual modes in pressure; one is the large-scale vortical structure in low frequency and the other is the boundary-layer-like decaying mode in high frequency.
An Experimental Study on the Effects of the Boundary Layer and Heat Transfer by Vortex Interactions ( I ) - On the common flow down -
Hong, Cheul-Hyun ; Yang, Jang-Sik ; Lee, Ki-Baik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 288~297
DOI : 10.22634/KSME-B.2000.24.2.288
This paper describes the results of an experimental investigation of the flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices. The test facility consists of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta wings(vortex generators) protruding from the surface. In order to control the strength of the two longitudinal vortices, the angles of attack of the vortex generators are varied from 20 degree to 45 degree, but spacings between the vortex generators are fixed to 4 cm. The 3-dimensional mean velocity downstream of the vortex generators is measured by a five-hole pressure probe, and the hue-capturing method using the thermochromatic liquid crystals has been used to provide the local distribution of the heat transfer coefficient. By using the method mentioned above, the following conclusions are obtained from the present experiment. The boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it is directed away from the wall. The peak augmentation of the local heat transfer coefficient occurs in the downwash region near the point of minimum boundary-layer thickness. Streamwise distributions of averaged Stanton number on the measurement planes show very similar trends for all the cases(
An Experimental Study on the Effects of the Boundary Layer and Heat Transfer by Vortex Interactions ( II ) - On the common flow up -
Han, Dong-Joo ; Yang, Jang-Sik ; Lee, Ki-Baik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 298~305
DOI : 10.22634/KSME-B.2000.24.2.298
The flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices were studied experimentally. The test facility consisted of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta wings protruding from the surface. In order to control the strength of the longitudinal vortices, the angles of attack of the vortex generators were varied from - 20 degree to - 45 degree, but spacings between the vortex generators were fixed to 4 cm. The 3-dimensional mean velocity measurements were made using a five-hole pressure probe. Heat transfer measurements were made using the thermochromatic liquid to provide the local distribution of the heat transfer coefficient. Unlike common flow down, common flow up vortices moved toward the centerline as they developed and interacted strongly with each other but not with the boundary layer. Spanwise profiles of Stanton number were similar for
, but not similar for
. The case of
showed the two peak Stanton number, but the case of
showed the only one peak Stanton number.
Identification of Internal Flow Pattern in Effervescent Atomizers
Kim, Joo-Youn ; Lee, Sang-Yong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 306~315
DOI : 10.22634/KSME-B.2000.24.2.306
An experimental study was conducted to examine the internal flow patterns inside the mixing chamber of effervescent atomizers. The mixing chamber has the rectangular cross section (
) and made of transparent acrylic plate for flow visualization. The parameters tested were the air/liquid ratio (ALR), injection. pressure, and the nozzle orifice diameter. Three different flow regimes were observed; bubbly, annular, and intermittent flows. In the bubbly flow regime, the discharged mixture was disintegrated into drops through the bubble expansion and the ligament breakup. On the other hand, in the annular flow regime, the liquid annulus was disintegrated into small drops by the aerodynamic interaction between the phases due to the high relative velocities between the gas and the liquid. In the intermittent flow regime, the bubble-expansion/ligament-disintegration mode and the annulus-disintegration mode appeared alternatively. The correlations representing the transition criteria between the two-phase flow patterns within the mixing chamber were proposed based on the drift-flux models.
A Non-linear Low-Reynolds-Number Heat Transfer Model for Turbulent Separated and Reattaching Flows
Rhee, Gwang-Hoon ; Sung, Hyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 2, 2000, Pages 316~323
DOI : 10.22634/KSME-B.2000.24.2.316
A nonlinear low-Reynolds-number heat transfer model is developed to predict turbulent flow and heat transfer in separated and reattaching flows. The
model of Park and Sung (1997) is extended to a nonlinear formulation, based on the nonlinear model of Gatski and Speziale (1993). The limiting near-wall behavior is resolved by solving the
elliptic relaxation equation. An improved explicit algebraic heat transfer model is proposed, which is achieved by applying a matrix inversion. The scalar heat fluxes are not aligned with the mean temperature gradients in separated and reattaching flows; a full diffusivity tensor model is required. The near-wall asymptotic behavior is incorporated into the
function in conjunction with the
elliptic relaxation equation. Predictions of the present model are cross-checked with existing measurements and DNS data. The model preformance is shown to be satisfactory.