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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
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 20, Issue 12 - Dec 1996
Volume 20, Issue 11 - Nov 1996
Volume 20, Issue 10 - Oct 1996
Volume 20, Issue 9 - Sep 1996
Volume 20, Issue 8 - Aug 1996
Volume 20, Issue 7 - Jul 1996
Volume 20, Issue 6 - Jun 1996
Volume 20, Issue 5 - May 1996
Volume 20, Issue 4 - Apr 1996
Volume 20, Issue 3 - Mar 1996
Volume 20, Issue 2 - Feb 1996
Volume 20, Issue 1 - Jan 1996
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Flow characteristics of supersonic twin-fluid atomizers
Park, Byeong-Gyu ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2267~2276
DOI : 10.22634/KSME-B.19184.108.40.2067
Twin-fluid atomization has been widely used in combustors and process industries because of its high performance and simple structure. Flow visualization and pressure measurements were conducted to investigate the effects of gas flow in twin-fluid atomization. Schlieren photographs showed that changes in atomizing gas pressure, altered the wave patterns, and the lengths of both recitrculating toroid (impinging stangnation point) nad supersonic flow region in the jet. A longer supersonic wave pattern like net-shape wqas observed as atomizing gas pressure increased. The disintegration phenomenon of liquid delivery tube. The variation of spray angles with gas pressures were obtained by visualization using laser sheet beam. Suction pressuresat the nozzle orifice exit and recirculating region are shown to be used to estimate the stable atomization condition of a twin-fluid atomizer.
Heat transfer and pressure drop with the turbulence promoter in a vertical PCB Channel
Park, Chan-U ; Jang, Seung-Il ; Jeong, Jong-Su ; Nam, Pyeong-U ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2277~2288
DOI : 10.22634/KSME-B.19220.127.116.117
This study was performed to analyze the cooling effect of heated ribs which are frequently used for cooling of electronic parts, using the numerical method. To prevent the excessive pressure drop due to turbulence promoters for the enhancement of heat transfer rate especially, the effect of the angle of turbulence promoter was investigated by the numerical analysis. Heat transfer rate with turbulence promoters with rectangular cross-section increased by 13% in average, but the coefficient of pressure drop increased by 1.68 times than that without them. In the present study, triangular cross-sectional shape turbulence promoters were suggested and numerically tested. Pressure drop of turbulence promoter with the 30 degree triangular cross-sectional shape decreased by 30% from that of rectangular cross-section promoters while heat transfer rate was almost the same. While with 4 turbulence promoters, the heat transfer rate increased by 21%, the pressure drop increased 4 times. It means that the higher capacity of cooling fan should be needed. With the triangular cross-sectional shape, the size of vortex region at the rear of promoters became considerably smaller, so pressure drop became smaller. The effect of the change of cross-sectional shape was not found in the flow pattern near the ribs, so that heat transfer characteristics in the ribs were not changed.
Characteristics of in-cylinder flow near the spark-plug for different engine speeds
Seong, Baek-Gyu ; Jeon, Gwang-Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2289~2297
DOI : 10.22634/KSME-B.1918.104.22.1689
Flows in the combustion chamber near the spark plug are measured using LDv.A single cylinder DOHC S.I. engine of compression ratio 9.5:1 with a transparent quartz window piston is used. Combustion chamber shape is semi-wedge type. Measured data are analyzed using the ensemble averaged analysis and the cycle resolved analysis which uses FFT Filtering. Turbulent intensity and mean velocity are studied in the main flow direction and the normal to main flow direction as a function of engine speeds. The results shows that the turbulent intensity obtained by the ensemble averaged analysis is greater than that calculated by the cycle resolved analysis. Especially, the ensemble averaged analysis shows increase in turbulence at the end of compression stroke although the cycle resolved analysis shows increase only in the cycle-by-cycle variation with no noticeable increase in turbulence. The mean velocity in the main flow direction increase as engine speed increase. But the mean velocity normal to the main flow does not show such increase. Turbulent intensity in both direction increase in proportion to engine speeds. The magnitude of turbulent intensity is about 0.3 ~ 0.4 times the mean piston speeds at the end of the compression stroke.
An experimental study for boiling heat transfer enhancement under electric fields
O, Si-Deok ; Gwak, Ho-Yeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2298~2314
DOI : 10.22634/KSME-B.1922.214.171.1248
Electric field effect on boiling of refrigerants R11, R113, and FC72 has been investigated experimentally. One purpose of the experimental investigation is to determine the effects of the electrode arrangements on electrohydrodynamic boiling of the above mentioned liquids. The test equipment employed in the experiment consists of a shell and tube heat exchanger with six or six and twelve rows of electrode wires around the tube. It has been found that the applied voltage promotes the boiling heat transfer coefficient except FC72. Boiling heat transfer enhancement obtained is about 230% for R11, 280% for R113. It has also been observed that bubbles detached from the tube aggregate at the place where the electrical gradient force balances with the buoyancy one. These aggregated bubbles force to decrease the boiling heat transfer coefficient as well as to reduce the voltage needed to the dielectric breakdown.
Numerical study on attenuation and distortion of compression wave propagation into a straight tube
Kim, Hui-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2315~2325
DOI : 10.22634/KSME-B.19126.96.36.1995
A compression wave is attenuated or distorted as it propagates in a tube. The present study investigated the propagation characteristics of the compression waves which are generated by a train in a high-speed railway tunnel. A Total Variation Diminishing (TVD) difference scheme was applied to one-dimensional, unsteady viscous compressible flow. The numerical calculation involved the effects of wall friction, heat transfer and energy loss due to the friction heat in the boundary layer behind the propagating compression wave, and compared with the measurement results of a shock tube and a real tunnel. The present results show that attenuation of the compression wave in turbulent boundary layer is stronger than in laminar boundary layer, but nonlinear effect of the compression wave is greater in the laminar boundary layer. The energy loss due to the frictional heat had not influence on attenuation and distortion of the propagating compression waves.
An Experimental Study on Flame Structure and Combustion Characteristics of Turbulent Diffusion Flame(III)
Jang, In-Gap ; Choe, Gyeong-Min ; Choe, Byeong-Ryun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2326~2336
DOI : 10.22634/KSME-B.19188.8.131.526
So most practical combustor is considered to the swirl flame, it is very important to examinate swirl flame structure and combustion characteristics. Recently, attention has been paid to the flame diagnostic by radical luminous intensity. For swirl flame structure and combustion characteristic, reverse flow boundary, temperature, ion current and radical luminous intensity were measured in the double-coaxial swirl combustor which was used principle of multi-annular combustor. This study had three experimental condition, S-type, C-type, SC-type. S-type and C-type flames were formed recirculation zone, but SC-type flame wasn't formed. C-type flame had two recirculation zone. The position with maximum value of ion current and CH-radical, temperature and OH-radical had similarity distribution almost. Therefore, it is possible that the macro structure of flame was measured by radical luminous intensity in the high intensity of turbulent combustion field which was formed by swirl.
An experimental study on microstructure of doubled jet burner flame
Jang, In-Gap ; Choe, Gyeong-Min ; Choe, Byeong-Ryun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2337~2346
DOI : 10.22634/KSME-B.19184.108.40.2067
One of the most useful method for increasing combustion loading of premixed flame is to strengthen the turbulent intensity of unburned mixture. It produces an important information to a design of efficient combustion equipment that analysing microstructure of strong turbulence premixed flame. The flame structure and characteristics are depend on the turbulence of unburned mixture. Therefore, to strengthen the turbulent intensity of unburned mixture make flame scale small and accomplish efficient combustion. We measured the velocity of local flame front movements, local eddy radius and local reaction zone thickness quantitatively with increasing turbulent intensity of unburned mixture. We researched the microstructure of flame using ion currents that react sensitively in the reaction zone. Consequently, the velocity of local flame front movements is depend on the velocity of unburned mixture and local eddy scale is to be small with increasing turbulent intensity. But there is no change in local reaction zone thickness with turbulence.
Numerical optimization design by computational fluid dynamics
Lee, Jeong-U ; Mun, Yeong-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2347~2355
DOI : 10.22634/KSME-B.19220.127.116.117
Purpose of the present study is to develop a computational design program for shape optimization, combining the numerical optimization technique with the flow analysis code. The present methodology is then validated in three cases of aerodynamic shape optimization. In the numerical optimization, a feasible direction optimization algorithm and shape functions are considered. In the flow analysis, the Navier-Stokes equations are discretized by a cell-centered finite volume method, and Roe's flux difference splitting TVD scheme and ADI method are used. The developed design code is applied to a transonic channel flow over a bump, and an external flow over a NACA0012 airfoil to minimize the wave drag induced by shock waves. Also a separated subsonic flow over a NACA0024 airfoil is considered to determine a maximum allowable thickness of the airfoil without separation.
An experimental study on the cooling characteristics of electronic cabinet
Park, Jong-Heung ; Lee, Jae-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2356~2366
DOI : 10.22634/KSME-B.1918.104.22.1686
High-power electronic chips have been advanced to such an extent that the heat dissipation capability of a system design has become one of the primary limiting factors. Therefore, thermal design must be considered in the early stage of the electronic system development. In present paper, the results of an experimental study on the forced convection cooling are presented to evaluate cooling performance of an electronic cabinet which in generally used for telecommunication system. Temperatures and thermal resistances are applied to compare the heat transfer characteristics for various locations of a fan unit as well as various configuration of non-uniform powering modules. As a result, the optimal configuration of a fan unit and powering configuration is suggested for the effective thermal design of telecommunication system.
A generalized scheil equation for the dendritic solidification of binary alloys
Yu, Ho-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2367~2374
DOI : 10.22634/KSME-B.1922.214.171.1247
A generalized Scheil equation for the solute redistribution in the absence of the back diffusion during the dendritic solidification of binary alloys is derived, in which coarsening of the secondary dendrite arms is taken into account. The obtained equation essentially includes the original Scheil equation as a subset. Calculated results for typical cases show that the coarsening affects the microsegregation significantly. The eutectic fraction predicted for coarsening is considerably smaller than that for fixed arm spacing. The most important feature of the present equation in comparison with the Scheil equation lies in the fact that there exists a lower limit of the initial composition below which the eutectic is not formed. Based on the generalized Scheil equation and the lever rule, a new regime map of the eutectic formation on the initial composition-equilibrium partition coefficient plane is proposed. The map consists of three regimes: the eutectic not formed, conditionally formed and unconditionally formed, bounded by the solubility and diffusion controlled limit lines.
Experimental study on reduction of impulsive noise generating at exit of high-speed railway tunnel
Kim, Hui-Dong ; Setoguchi, Toshiaki ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2375~2385
DOI : 10.22634/KSME-B.19126.96.36.1995
As a compression wave is emitted from a duct, an impulsive wave generates and causes an impulsive noise that is at present a serious environmental noise pollution. In order to clarify the acoustic characteristics of the noise and to reduce their pressure levels, a series of model experiments were conducted on the impulsive waves emitted from an open end of a shock tube. The impulsive waves with various intensities were obtained by controlling the operation pressure ratio of the shock tube. Various kinds of silencers such as the exit boxes with baffle plates, were applied to the duct exit to reduce the impulsive noises. The effects of geometry of silencers and shock Mach number on the noise reduction were clarified. From the measurements of sound pressure level, it was found that installing the baffle plate into the exit box is effective in lowering the noise level at far fields, and that the recommendable geometries of silencer are L/D=1, H/D=1 and H/D=0.75.
Prediction of Isothermal and Reacting Flows in Widely-Spaced Coaxial Jet, Diffusion-Flame Combustor
O, Gun-Seop ; An, Guk-Yeong ; Kim, Yong-Mo ; Lee, Chang-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2386~2396
DOI : 10.22634/KSME-B.19188.8.131.526
A numerical simulation has been performed for isothermal and reacting flows in an exisymmetric, bluff-body research combustor. The present formulation is based on the density-weighted averaged Navier-Stokes equations together with a k-epsilon. turbulence model and a modified eddy-breakup combustion model. The PISO algorithm is employed for solution of thel Navier-Stokes system. Comparison between measurements and predictions are made for a centerline axial velocities, location of stagnation points, strength of recirculation zone, and temperature profile. Even though the numerical simulation gives acceptable agreement with experimental data in many respects, the present model is defictient in predicting the recoveryt rate of a central near-wake region, the non-isotropic turbulence effects, and variation of turbulent Schmidt number. Several possible explanations for these discrepancies have been discussed.
Control of oscillatory Czochralski convection by ACRT
Choe, Jeong-Il ; Seong, Hyeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2397~2408
DOI : 10.22634/KSME-B.19184.108.40.2067
A numerical study was made of the control of transient oscillatory flow modes in Czochralski convection. The reduction of temperature oscillation was achieved by changing the rotation rate of crystal rod, .OMEGA.
t)). The temporal behavior of oscillation flow was scrutinized over broad ranges of two parameters, i.e., the rotation amplitude(
.leq.0.5) and the nondimensional frequency (0.9.leq.
.leq.1.5). The mixed convection parameter was ranged 0.225.leq.Ra/PrR
.leq.0.929, which encompassed the buoyancy-and forced-dominant convection regimes. Computational results revealed that the temperature oscillations could be reduced effectively by a proper adjustment of the control parameters. The uniformity of temperature distribution near the crystal rod was examined. The control of oscillatory flow modes was also made for a realistic, low value of Pr.
Program Development for Design and Part Load Performance Analysis of Single-Shaft Gas Turbines
Kim, Dong-Seop ; No, Seung-Tak ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2409~2420
DOI : 10.22634/KSME-B.19220.127.116.119
This paper describes the development of a general program for the design and part load performance analysis of single-shaft-heavy-duty gas turbines. Efforts are made to fully represent the real component features by the characteristic models and special emphasis is put on the modeling of cooled turbine stages. The design analysis routine is applied to simulate the performance of current gas turbines and its appropriateness for system analysis is validated. Meanwhile, the component parameters of real engines which describe the technology level are obtained. The program is extended to predicting the part load operation of gas turbines with the aid of models for the off-design characteristics of compressor, turbine and other main components. Part load simulation can be carried out only with limited numbers of input data. It is demonstrated that the program accurately estimates the part load characteristics of real turbines.
A Study on the Smoke Reduction of Methanol-Diesel Engine
Han, Seong-Bin ; Mun, Seong-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 7, 1996, Pages 2421~2429
DOI : 10.22634/KSME-B.1918.104.22.1681
The objective of this research is to apply effect of the pre-mixed combustion quantity and smoke emission in diesel engine. According as air fuel ratio is increased, emission of smoke concentration is linearly reduced. As Injection timing is advanced, smoke concentration is remarkably reduced. It is considered to be the primary cause of the increase in the premixed combustible mixture during long ignition delay period with advancing injection timing. Smoke is increased with increasing engine speed, so it is considered to be the primary cause of the increase of the mass of fuel injected. Smoke is decreased according to the increase of methanol volume ratio. It is considered that the primary cause of the increase in the quantity of pre-mixed combustion.