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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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Development of a numerical flow model for the multi-cylinder engine intake system
Song, Jae-Won ; Seong, Nak-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1921~1930
DOI : 10.22634/KSME-B.1918.104.22.1681
To design an optimum engine intake system, a flow model for the intake manifold was developed by the finite difference method. The flow in the intake manifold was one-dimensional, and the finite difference equations were derived from governing equations of flow, continuity, momentum and energy. The thermodynamic properties of the cylinder were found by the first law of thermodynamics, and the boundary conditions were formulated using steady flow model. By comparing the calculated results with experimental data, the appropriate boundary conditions and convergence limits for the flow model were established. From this model, the optimum manifold lengths at different engine operating conditions were investigated. The optimum manifold length became shorter when the engine speeds were increased. The effect of intake valve timings on inlet air mass was also studied by this model. Advancing intake valve opening decreased inlet air mass slightly, and the optimum intake valve closing was found. The difference in inlet air mass between cylinders was very small in this engine.
Effect of Periodic Passing Wake on the Flow Field of a Film-Cooled Flat Plate(I)
Guk, Geon ; Lee, Jun-Sik ; Go, Sang-Geun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1931~1940
DOI : 10.22634/KSME-B.1922.214.171.1241
The effect of periodic passing wake on the film-coolant flow issuing normally from a flat plate was investigated experimentally. The passing wake was generated by rotating thin circular bars. Depending on the rotational direction the test plate could be simulated as a pressure surface or a suction surface of a gas turbine blade. The phase-averaged velocity components were measured using an X-type hot-wire probe. The Reynolds number based on the free-stream velocity and injection hole diameter was 23, 500 and the velocity ratio which is the ratio of film coolant velocity to free-stream velocity was 0.5. The velocity-triangle induced by the wake was similar to that induced by the one generated at the blade trailing edge. The vertical velocity component induced by the passing wake, which approaches to the suction surface and moves away from the pressure surface, played a dominant role in the variation of the flow field. The variation in the phase-averaged velocity on the pressure surface was greater than on the suction surface, but the turbulence kinetic energy variation on the suction surface appeared larger than on the pressure surface.
Spray characteristics and nozzle design experiment to twin-fluid atomizer
Jeong, Jin-Do ; Ji, Pyeong-Sam ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1941~1947
DOI : 10.22634/KSME-B.19126.96.36.1991
Droplet size measurement technique was established for the sprayed viscous fluid by virtue of the installation of the sprayed-droplet size measurement system employing light scattering method. Atomization test results showed that the mean droplet size of the sprayed viscous fluid is decreased with the increase of the mass ratio of air to fuel and in case of the same air/fuel ratio, also with the increase of viscous fluid flow rate, and is increased with the distance from atomizer tip. Basic design data for the manufacture of external-mixing type, Y-Jet type, and internal-mixing type atomizers was acquired from the atomization tests.
Spray modelization of air-assisted coaxial atomizer
Yun, Seok-Ju ; Ledoux, M. ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1948~1958
DOI : 10.22634/KSME-B.19188.8.131.528
Experimental and theoretical studies on the air-assist coaxial atomizer have been continuously carried out for a long time. But now the importance of the theoretical study is tending to increase as with the development of computer. This study is concerned to the spray modelization, especially, the instability of the liquid jet surrounded by the air stream which flows with high velocity. To study the phenomena of the break up, we used the linear theory based on the classical Kelvin-Helmholtz theory for capillary wave at a simple interface and we investigated the variation of liquid core radius. As a result, we obtained that the drop diameter and the variation of the liquid core radius predicted by using our model are reasonable.
Experimental investigation on the heat transfer characteristics of an oscillatory pipe flow
Park, Sang-Jin ; Lee, Dae-Yeong ; No, Seung-Tak ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1959~1970
DOI : 10.22634/KSME-B.19184.108.40.2069
Effects of oscillatory flow upon heat transfer characteristics have been studied experimentally for oscillating flow in a circular tube. The experimental apparatus was designed to simulate the heat exchangers of the Stirling or Vuilleumier cycle machines and the test section consists of heater and cooler. Measurements were presented of heat flux, axial wall temperature distribution, and radial temperature profile of the working fluid for several cases of oscillation frequency and swept distance ratio. The influences of two main parameters, frequency and tidal displacement of the oscillation were investigated. Then the heat transfer coefficient at the heater is obtained. The carried by the authors with a assumption of oscillatory laminar slug flow.
Calculation of the internal flow in a fuel nozzle
Gu, Ja-Ye ; Park, Jang-Hyeok ; O, Du-Seok ; Jeong, Hong-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1971~1982
DOI : 10.22634/KSME-B.19220.127.116.111
The breakup of liquid jet is the result of competing, unstable hydrodynamic forces acting on the liquid jet as it exit the nozzle. The nozzle geometry and up-stream injection conditions affect the characteristics of flow inside the nozzle, such as turbulence and cavitation bubbles. A set of calculation of the internal flow in a single hole type nozzle were performed using a two dimensional flow simulation under different nozzle geometry and up-stream flow conditions. The calculation showed that the turbulent intensity and discharge coefficient are related to needle position. The diesel nozzle with sharp inlet under actual engine condition has possibility of cavitation, but round inlet nozzle has no possibility of cavitation.
Vaporization and condensation of metallic species in hazardous waste incineration
Song, Yu-Seok ; Hwang, Jeong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1983~1993
DOI : 10.22634/KSME-B.1918.104.22.1683
For selected (pure and compound) metallic species effects of saturation ratio, temperature, particle size and number density on condensation mechanisms are first reviewed. The tendencies for vaporization and condensation differ between metallic species because of the significant differences in their saturation pressures. Then particle pressure of a metal vapor species at incineration temperature is calculated by simplifying waste as a compound of methane, chlorine and small amounts of metals and assuming a thermodynamic equilibrium state. Next the condition is assessed for which supersaturation of combustion gases by the species above the critical level for homogeneous condensation may occur, when the gases contain a large number of pre-existing particles such as entrained ashes. Regardless of the presence of chlorine in the waste, the homogeneous condensation of PbO vapors may occur, depending on number density of the pre-existing particles. However, when chlorine exists in the waste, the homogeneous condensation of PbCl
vapors does not occur, which is similar to the case of Cd and Hg vapors. Thus these highly volatile species, PbCl
, Cd, and Hg, may emit to atmosphere as vapor phase. In general, for reducing the emission of hazardous metallic species into the atmosphere, the number density of pre-existing particles has to be increased. For fixed particle number density, the temperature drop rate must be kept in low if the temperature at which a condensable vapor species emits from a incineration system is fixed, while the temperature drop rate must be kept in high if the residence time for which a condensable species stays in the system is fixed.
Numerical Study on Under-Expanded Jets through a Supersonic Nozzle(II)
Kim, Hui-Dong ; Sin, Hyeong-Seung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 1994~2004
DOI : 10.22634/KSME-B.1922.214.171.1244
Numerical calculation was applied to supersonic under-expanded jets, and compared with the results of a linear theory and other experiments. TVD difference scheme was employed to solve 2-dimensional and axisymmetric inviscid Euler equation. This paper aims to explore the effects of angle of divergence and design Mach number of nozzle on the structure of under-expanded jets. The angle of divergence was varied from 0 to 20 deg. The results show that the length of the first cell of the under-expanded jets decreases and Mach disk generates at lower nozzle pressure ratio, if the angle of divergence or design Mach number of nozzle increases. The distance from the nozzle exit to Mach disk in 2-dimensional jets becomes much larger than that of axisymmetric jets, and the widths of the jet boundary and the barrel shock wave are also larger than that of axisymmetric jets. Calculation results indicate that the configuration of the under-expanded jets is strongly dependent on the nozzle pressure ratio.
Particle path and performance evaluation of differential mobility analyzer
An, Gang-Ho ; Kim, Nam-Hyo ; Lee, Jong-Ho ; Bae, Gwi-Nam ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 2005~2013
DOI : 10.22634/KSME-B.19126.96.36.1995
Particle paths and flow fields in a prototype differential mobility analyzer (DMA) were numerically analyzed solving Navier-Stokes equation, electric field equation and particle motion considering viscous drag force, Coulomb force and polarization force. Analytically predicted particle diameters for the prototype DMA are in good agreement with the measured particle diameters within
1%. And the analytically predicted particle diameters are also in good agreement with numerical results for the prototype DMA.
Flow structure of wake behind a finite circular cylinder
Lee, Sang-Jun ; Jeong,Yong-Sam ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 2014~2022
DOI : 10.22634/KSME-B.19188.8.131.524
Flow characteristics of the wake behind a finite circular cylinder(FC) mounted on a flat plate was experimentally investigated. Three finite cylinder models having aspect ratio (length to diameter ratio, L/D) of 6,10 and 13 were tested in this study. Wake velocity was measured by a hot-wire anemometry at Reynolds number of 20,000, and the results were compared with those of two-dimensional circular cylinder. As a result, the free-end effect on the wake structure becomes more dominant with decreasing the aspect ratio(L/D) of the finite cylinder. Invisid flow entrained into the wake region decreases the turbulence intensity and periodicity of the vortex shedding due to existence of the free end. From spectral analysis and cross correlation of the velocity signals, vortices having 24Hz frequency characteristics are found in the down wash flow just behind the free end. There exists very complicated flow near the free end due to interaction between the entrained flow and streamwise vortices. Vortex formation region is destroyed significantly in the near wake and shows quite different wake structures from those of 2-D cylinder.
A study on the deformation of a bubble and a drop in a uniform electric field
Gwon, Yeong-Cheol ; Kim, Mu-Hwan ; Gang, In-Seok ; Cho, Hae-Jung ; Kim, Suk-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 2023~2035
DOI : 10.22634/KSME-B.19184.108.40.2063
In the present study, the characteristics of the electrical deformation of a bubble and a drop under a uniform electric field have been investigated to understand EHD heat transfer enhancement by an electric field. The deformation of the bubble and the drop have been studied theoretically using an electric normal stress acting on their interfaces and assured by the numerical analysis and the experiment. From the variation of bubble volume and free energy, it is found that a bubble is compressed in an electric field and free energy had larger value with increasing W and the permittivity of a dielectric fluid. The electric normal stress induced on the interface of the bubble and the drop is different. Because of the surface charge induced at the drop interface, the electric normal stress acting on the drop is much larger than that of the bubble. The drop is, therefore, deformed much more than the bubble. In addition, the experimental and numerical results show that the aspect ratio and the contact angle of the bubble increase with increasing W.
Effects of environmental flow velocity on the evaporation of free droplets
Jeong, Seong-Sik ; Ha, Jong-Ryul ; Lee, Jung-Sun ; Lee, Sang-Seok ; Kawaguchi, O ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 2036~2045
DOI : 10.22634/KSME-B.19220.127.116.116
An experimental study has been performed to obtain the effect of relative velocity between droplet and environmental gas on the evaporation of a n-heptane free droplet of 180
m in diameter flying in a hot and normal pressure air flow. Measurement of droplet diameter and velocity was conducted in a series of time by an electrically controlled optical system. From the experimental results, an empirical equation associated with the relation between evaporation rate constant and relative velocity was obtained.
Thermal instability during the melting process in an isothermally heated horizontal cylinder
Jeong, Jae-Dong ; Yu, Ho-Seon ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 2046~2056
DOI : 10.22634/KSME-B.1918.104.22.1686
The constrained melting inside an isothermally heated horizontal cylinder has been repeatedly investigated in many studies only for the moderate Rayleigh numbers. This study extends the range of Rayleigh numbers to systematically investigate the transition during melting processes, especially focusing on the complex multi-cellular flow pattern and thermal instability. The enthalpy-porosity formulation, with appropriate source terms to account for the phase change, is employed. For low Rayleigh numbers, initially developed single-cell base flow keeps the flow stable. For moderate Rayleigh numbers, even small disturbances in balance between thermal buoyance force and viscous force result in branched flow structure. For high Rayleight numbers, Benard type convection is found to develop within a narrow gap between thee wall and the unmelted solid. The marginal Rayleigh number and the corresponding wave number are in excellent agreement with those from linear stability theory.
Comparison of engine fault diagnostic techniques using the crankshaft speed fluctuation
Kim, Se-Ung ; Bae, Sang-Su ; Kim, Eung-Seo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 6, 1996, Pages 2057~2066
DOI : 10.22634/KSME-B.1922.214.171.1247
^In this paper, diagnostic technique for detecting the engine faults, especially misfire, are introduced and compared with each other under the same conditions. With all of them the instantaneous angular velocitys, measured at the flywheel, were analyzed. The techniques include the frequency analysis, auto-correlation function, velocity index, acceleration index, maximum acceleration index, and integrated torque index. Since the main driving components for the angular velocity fluctuation are both the pressure and the inertia torque, the component of the inertia torque in it must be excluded to extract the information of the combustion from the angular velocity. To do this, it is required to consider only the first half of the combustion period in the angular velocity fluctuations, which has never been proposed in the existing methods. On the basis of this fact, the results show that the most effective diagnostic technique is maximum acceleration index.