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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 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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Numerical and Experimental Analyses of the Aerodynamic Characteristics of a Counter Rotating Axial Fan
Cho, Jin-Soo ; Won, Yu-Phil ; Lee, Moon-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 325~337
DOI : 10.22634/KSME-B.2000.24.3.325
A study was done on the numerical and experimental analyses of the aerodynamic characteristics of a counter rotating axial fan. The numerical analysis uses the frequency domain panel method developed for the aerodynamic analysis of interacting rotating systems, which is based on the unsteady lifting surface panel method. Each stage of interaction involves the solution of an isolated rotor, the interaction being done through the Fourier transform of the induced velocity field. Numerical results showed good agreements with other experimental data for single and counter rotating propeller systems. And they were compared with the experimental results of the counter rotating axial fan studied in the present paper. The performance test was carried out based on the Korean Standard (KS B 6311). It was focused on the relative efficiency increase of a counter rotating system for a single rotating one, and effects of the axial distance between the front and rear rotors on overall fan performances were investigated. As a result, it was shown that the counter rotating axial fan has the efficiency 14% higher than the single rotating one at peak efficiency points.
An Experiment on the Flow Control Characteristics of a Passive Fluidic Device
Seo, Jeong-Sik ; Song, Chul-Hwa ; Cho, Seok ; Chung, Moon-Ki ; Choi, Young-Don ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 338~345
DOI : 10.22634/KSME-B.2000.24.3.338
A model testing has been performed to investigate the flow characteristics of a vortex chamber, which plays a role of a flow switch and passively controls the discharge flow rate. This method of passive flow control is a matter of concern in the design of advanced nuclear reactor systems as an alternative to the active flow control to provide emergency water to the reactor core in case of postulated accidents like LOCA (Loss-Of-Coolant Accident). By changing the inflow direction in the vortex chamber and varying the flow resistance inside the chamber, the vortex chamber can control passively the injection flowrate. Fundamental characteristics such as discharge flow rate and pressure drop of the vortex chamber are measured, and its parametric effects on the performance of the vortex chamber are also systematically investigated.
A Study on the Heat Transfer Characteristics of Loop Type Capillary Heat Pipe
Yoon, Suck-Hun ; Choi, Jae-Hyuck ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 346~353
DOI : 10.22634/KSME-B.2000.24.3.346
In this paper, heat transfer characteristics of a loop type capillary heat pipe were experimentally investigated for the effect of several fill charge ratios of working fluid and heat loads. This type of heat pipe consists of a heating section, a cooling section and an adiabatic section. The heat pipe used has a 0.002m internal diameter, a 0.34m length in one turn and consists of 19 turns. Heating and cooling sections each have a length of 70mm. Experiments were performed to measure the temperature distributions and the pressure variation of the heat pipe. Heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients were calculated for various operating conditions of heat pipe and it was found that heat transfer characteristics of this type heat pipe were very excellent. As shown by this experimental study, this type of heat pipe operates by oscillatory flow caused by pressure and temperature oscillations.
A Study on Identification of State-Space Model for Refuse Incineration Plant
Hwang, l-Cheol ; Jeon, Chung-Hwan ; Lee, Jin-Kul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 354~362
DOI : 10.22634/KSME-B.2000.24.3.354
This paper identifies a discrete-time linear combustion model of Refuse Incineration Plant(RIP) which characterizes steam generation quantity, where the RIP is considered as a MIMO system with thirteen-inputs and one-output. The structure of RIP model is described as an ARX model which are analytically obtained from the combustion dynamics. Furthermore, using the Instrumental Variable(IV) identification algorithm, model structure and unknown parameters are identified from experimental input-output data sets, In result, it is shown that the identified ARX model well approximates the input-output combustion characteristics given by experimental data sets.
Performance of Evaporation Heat Transfer Enhancement and Pressure Drop for Liquid Nitrogen
Nam, Sang-Chul ; Lee, Sang-Chun ; Park, Byung-Duck ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 363~372
DOI : 10.22634/KSME-B.2000.24.3.363
An experiment was carried out to evaluate the heat transfer enhancement and the pressure drop characteristics for liquid nitrogen using wire-coil-insert technique under horizontal two-phase conditions. The tube inner diameters were 8 mm and 15 mm, respectively and the tube length was 4.7 m. The helix angle of the wire coil insert was
and its length was 4.7 m. Heat transfer coefficients for both the plain and the enhanced test tubes were calculated from the measurements of temperatures, flow rates and pressure drops. A correlation in a power-law relationship of the Nusselt number, Reynolds number and Prandtl number for the heat transfer was proposed which can be available for design of cryogenic heat exchangers. The correlation showed that heat transfer coefficients for the wire-coil inserts were much higher than those for plain tubes, increased by more than
times depending upon the range of the equivalent Reynolds number. The correlation was compared with other various correlations in the turbulent flow conditions.
Heat Transfer Characteristics on Impingement Surface with Control of Axisymmetric Jet ( 2 ) - With Acoustic Excitation -
Hwang, Sang-Dong ; Lee, Chang-Ho ; Cho, Hyung-Hee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 373~381
DOI : 10.22634/KSME-B.2000.24.3.373
The flow and heat transfer characteristics on the impingement surface can be controlled by the change of vortex with the acoustic excitation, because the flow characteristics of an impinging jet are affected strongly by the vortices formed at the jet exit. To investigate the effects of acoustic excitation, we measured the velocity, turbulent intensity distributions for the free jet and local heat transfer coefficients on a impingement surface. As the acoustic excitation, subharmonic frequency of excited frequency plays an important role to the control of the jet flow. If the vortex pairings are promoted by the acoustic excitation, turbulence intensity of the jet flow is increased quickly. On the other hand if the vortex pairings are suppressed, the jet flow has low turbulence intensity at the center of the jet. Therefore, the low heat transfer rates are obtained on the impingement plate for a small nozzle-to-plate distance. However, it has high heat transfer rates at a large distance between the nozzle and plate due to the increasing of potential-core length.
PIV Measurements of Flow and Turbulence Characteristics of Round Jet in Crossflow
Kim, Kyung-Chun ; Kim, Sang-Ki ; Yoon, Sang-Youl ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 382~389
DOI : 10.22634/KSME-B.2000.24.3.382
The instantaneous and ensemble averaged flow characteristics of a round jet issuing normally into a crossflow was studied using a flow visualization technique and Particle Image Velocimetry measurements. Experiments were performed at a jet-to-crossflow velocity ratio, 3.3, and two Reynolds numbers, 1050 and 2100, based on crossflow velocity and jet diameter. Instantaneous laser tomographic images of the vertical center plane of the crossflow jet showed that there exist very different natures in the flow structures of the near field jet even though the velocity ratio is the same. It was found that the shear layer becomes much thicker when the Reynolds number is 2100 due to the strong entrainment of the inviscid fluid by turbulent interaction between the jet and crossflow. The mean and second order statistics were calculated by ensemble averaging over 1000 realizations of instantaneous velocity fields. The detail characteristics of mean flow field, stream wise and vertical r.m.s. velocity fluctuations, and Reynolds shear stress distributions were presented. The new PlV results were compared with those from previous experimental and LES studies.
Prediction of Nitric Oxide Formation Using a Two-Zone Model in a DI Diesel Engine
Kim, Cheol-Hwan ; Lee, Jin-Ho ; Chun, Kwang-Min ; Lee, Kyo-Seung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 390~401
DOI : 10.22634/KSME-B.2000.24.3.390
In this study, numerical calculation is carried out to investigate the influence of injection timing, fuel amount, intake
concentration, and EGR on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows. The NO formation is very sensitive to the burned gas temperature, so multi-zone model must be applied to combustion process to predict the burned gas temperature exactly. Since the burned gas temperature increases rapidly during the premixed combustion, most NO is formed within 20 crank angle degrees after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result, NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine. As the intake
concentration increases, the maximum pressure and burned gas temperature increase due to activate combustion. And, [O] mole fraction of equilibrium combustion products also increase. Therefore NO exponentially increases. If exhaust gas is recirculated, the burned gas temperature decreases which results in NO decrease. If exhaust gas is cooled, more NO can be decreased.
An Experimental Study on the Combustion Characteristics of CWM Single Droplet
Park, Chong-Sang ; Lee, Tae-Won ; HA, Jong-Yul ; Chung, Sung-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 402~410
DOI : 10.22634/KSME-B.2000.24.3.402
As the combustion process of CWM consists of the water evaporation, the release and combustion of volatile matter, and the combustion of char for every particle, it is more complex than that of existent liquid fuel. Though the many studies on CWM combustion have been carried out by the single droplet using hanging methods or the multiple droplet using atomization methods, any report don't presents definite solution about the effects by the initial water evaporation and combustion of volatile. When CWM is suddenly exposed in the high temperature surroundings, the internal water evaporates and then each droplet builds up pores. Besides, porosity rate changes along the temperature of surroundings, the composition ratio of CWM, and the initial diameter of droplet. In result, because it affects the whole combustion rate, the combustion of CWM has complex mechanism as compared with the combustion of liquid or gas fuel. Therefore, concentrating on porous structure of CWM, this study has proceeded to acquire the basic data on the CWM injection combustion and closely examines the effects of the first stage combustion on the whole combustion by measuring the diameter variations, pore rate, mass fraction burned, and the internal temperature changes of CWM droplet. The results demonstrate that
of initial mass is reduced during water evaporation and volatile combustion period, and swelling rate, mass faction burned, and density variation are greatly concerned with atomization of CWM etc.
An Analytical Slip Factor Based on a Relative Eddy Size Model for Centrifugal Impellers
Paeng, Kee-Seok ; Chung, Myung-Kyoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 411~418
DOI : 10.22634/KSME-B.2000.24.3.411
By calculating the location and size of the relative eddy formed in the rotating impellers with the logarithmic spiral vanes, a new simple but accurate slip factor is analytically derived. The proposed slip factor depends on only one parameter that is a function of the number of vanes and the vane exit angle. Predicted slip factor for various cases are compared with those estimated by a number of previous slip factors as well as a recent theoretical calculation by Visser et al. ( JFM, Vol. 268, pp. 107-141, 1994). It is found that the present slip factor yields almost similar results to Wiesner's which has been empirically formulated based on the theoretical calculation of Busemann.
Pressure Drop and Heat Transfer Characteristics of Multi-Layer Screen
Song, Tae-Ho ; Ahn, Cheol-Woo ; Kim, Chang-Kee ; Ko, Hyun-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 419~425
DOI : 10.22634/KSME-B.2000.24.3.419
Multiple layer of wire screen is widely used in many compact devices to filter particulates and to heat or cool fluids. However, data of flow resistance and heat transfer through such layers are rare to find and thus they are experimentally investigated in this study. Compressed air is made to flow through it to find the Ergun constants over a wide range of the Reynolds number. Also, unsteady heating of the wire screen is performed to find the equivalent heat transfer coefficient between the screen and the air by fitting the unsteady air temperature. The obtained coefficients are expressed in terms of the Reynolds number and the Prandtl number.
An Extended Similarity Solution for One-Dimensional Multicomponent Alloy Solidification in the Presence of Shrinkage-Induced Flow
Chung, Jae-Dong ; Yoo, Ho-Seon ; Choi, Man-Soo ; Lee, Joon-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 426~434
DOI : 10.22634/KSME-B.2000.24.3.426
This paper deals with a generalized similarity solution for the one-dimensional solidification of ternary or higher-order multicomponent alloys. The present approach not only retains the existing features of binary systems such as temperature- solute coupling, shrinkage-induced flow, solid-liquid property differences, and finite back diffusion, but also is capable of handling a multicomponent alloy without restrictions on the partition coefficient and microsegregation parameter. For an alloy of N-solute species, governing equations in the mushy region reduce to (N+2) nonlinear ordinary differential equations via similarity transformation, which are to be solved along with the closed-form solutions for the solid and liquid regions. A linearized correction scheme adopted in the solution procedure facilitates to determine the solidus and liquidus positions stably. The result for a sample ternary alloy agrees excellently with the numerical prediction as well as the reported similarity solution. Additional calculations are also presented to show the utility of this study. Finally, it is concluded that the present analysis includes the previous analytical approaches as subsets.
Heat Transfer Characteristics on Effusion Plate in Impingement/Effusion Cooling for Combustor
Rhee, Dong-Ho ; Cho, Hyung-Hee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 435~442
DOI : 10.22634/KSME-B.2000.24.3.435
The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged for the two different ways: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5,000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the mid-line of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). More uniform and higher heat/mass transfer characteristic is obtained in overall region with small gap between two perforated plates.
Performance Improvement of 2-Frame PTV Method Using an Adaptive Hybrid Scheme
Kim, Hyoung-Bum ; Lee, Sang-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 443~449
DOI : 10.22634/KSME-B.2000.24.3.443
The performance of 2-frame PTV(particle tracking velocimetry) system was improved using an adaptive hybrid scheme. The original 2-frame PTV method based on the match probability concept employs global match parameters for the entire flow field. Since this does not reflect fully the detailed local velocity change, it sometimes reduces the recovery rate of velocity vectors and increases the number of erroneous vectors in the region where an extraordinary flow structure exists. In this study, the preliminary FFT-based PIV results are used as an input parameter to determine the local match parameters needed for the 2-frame particle tracking algorithm. A computer simulation using synthetic particle images was carried out to study the performance of the adaptive 2-frame PTV technique. The adaptive hybrid method shows the better performance with increasing the velocity vector recovery rate and decreasing the computation time, compared to the original 2-frame PTV method.
An Analytical Solution for the Unsteady Close-Contact Melting by Convective Heating
Yoo, Ho-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 450~458
DOI : 10.22634/KSME-B.2000.24.3.450
This study deals with the unsteady close-contact melting of solid blocks on a flat surface subject to convective heating. Normalizing the model equations in reference to the steady solution successfully leads them to cover constant heat flux and isothermal limits at small and large extremes of the Biot number, respectively. The resulting equations admit a compactly expressed analytical solution, which includes the previous solutions as a subset. Based on the steady solution, the characteristics of close-contact melting can be categorized into constant heat flux, transition, and isothermal regimes, the boundaries of which appear to be nearly independent of the contact force. The unsteady solutions corresponding to Biot numbers in the transition regime show intermediate behaviors between those of the two limits. With a proper approximation, the present solution procedure can cope with the case of variable fluid temperature and heat transfer coefficient. Regardless of imposed conditions, the mean normalized Nusselt number during the unsteady process asymptotically approaches to a constant value as the Biot number comes close to each limit.
Flow Analysis on Near Field of Elliptic Jet Using a Single-Frame PIV
Shin, Dae-Sig ; Lee, Sang-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 459~466
DOI : 10.22634/KSME-B.2000.24.3.459
Flow characteristics of turbulent elliptic jets were experimentally investigated using a single-frame PIV system. A sharp-edged elliptic nozzle with aspect ratio(AR) of 2 was tested and the experimental results were compared with those of circular jet having the same equivalent diameter(
). The Reynolds number based on the nozzle exit velocity and nozzle equivalent diameter was about
. The spreading rate along the major and minor axis are different remarkably. The jet half width along the major axis decreases at first and then increases with going downstream. But along the minor axis the jet width increases steadily. The elliptic jet of AR=2 has one switching points at
within the near field. Turbulence properties are also found to be significantly different along the major and minor axis planes.
Numerical Simulation of Turbulent Separated and Reattaching Flows by Local Forcing
Rhee, Gwang-Hoon ; Sung, Hyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 467~476
DOI : 10.22634/KSME-B.2000.24.3.467
An unsteady numerical simulation was performed for locally-forced separated and reattaching flow over a backward-facing step. The local forcing was given to the separated and reattaching flow by means of a sinusoidally oscillating jet from a separation line. A version of the
model was employed, in which the near-wall behavior without reference to distance and the nonequilibrium effect in the recirculation region were incorporated. The Reynolds number based on the step height (H) was fixed at
, and the forcing frequency was varied in the range
. The predicted results were compared and validated with the experimental data of Chun and Sung. It was shown that the unsteady locally-forced separated and reattaching flows are predicted reasonably well with the
model. To characterize the large-scale vortex evolution due to the local forcing, numerical flow visualizations were carried out.
Numerical Investigation of Contamination Particle's Trajectory in a Head/slider Disk Interface
Park, Hee-Sung ; Hwang, Jung-Ho ; Choa, Sung-Hoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 3, 2000, Pages 477~484
DOI : 10.22634/KSME-B.2000.24.3.477
Microcontamination caused by particle deposition on the head disk interface threatens the reliability of hard disk drive. Design of slider rail to control contamination becomes an important issue in magnetic recording. In this paper, how particles adhere to the slider and the disk is examined. To investigate accumulation mechanism of the particles, trajectory of the particles in a slider/disk interface is simulated with considering various forces including drag force, gravitational force, Saffman lift force, and electrostatic force. It is found that the charged particles can easily adhere to the slider or disk surface, if an electric field exists between the slider and the disk. It is supposed that the vertical motion of the particles should be related with not only Saffman force but also electrostatic force.