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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 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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Secondary flows through an impeller of centrifugal compressor at design and off-design conditions
Choe, Yeong-Seok ; Gang, Sin-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3573~3588
DOI : 10.22634/KSME-B.1918.104.22.16873
The flow through a centrifugal compressor impeller was calculated using the 3-dimensional Navier-Stokes solution method. A control volume method based on a rotating curvilinear coordinate system was used to solve the time-averaged Navier-Stokes equations, and a standard k-.epsilon. model was used to obtain eddy viscosity. Numerical results and experimental data were compared for the overall performance of the impeller, the pressure distributions along the shroud wall and the detailed flowfields at the design and off-design conditions, which showed good coincidence. The flow through the impeller is complex with the curvature of the streamlines and rotation. The development of secondary flows and the jet-wake flow characteristics, which is the main source of flow loss, was discussed. Calculation results show quite different patterns as the flow rate changes.
Simulation of Three-Dimensional Turbulent Flows around an Ahmed Body-Evaluation of Finite Differencing Schemes-
Myeong, Hyeon-Guk ; Park, Hui-Gyeong ; Jin, Eun-Ju ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3589~3597
DOI : 10.22634/KSME-B.1922.214.171.12489
The Reynolds-averaged Navier-Stokes equations with the equations of the k-.epsilon. turbulence model are solved numerically in a general curvilinear system for a three-dimensional turbulent flow around an Ahmed body. The simulation is especially aimed at the evaluation of three finite differencing schemes for the convection term, which include the upwind differencing scheme(UDS), the second order upwind differencing scheme(SOU scheme) and the QUICK scheme. The drag coefficient, the velocity and pressure fields are found to be changed considerably with the adopted finite differencing schemes. It is clearly demonstrated that the large difference between computation and experiment in the drag coefficient is due to relatively high predicted values of pressure drag from both front part and vertical rear end base. The results also show that the simulation with the QUICK or SOU scheme predicts fairly well the flow field and gives more accurate drag coefficient than other finite differencing scheme.
Thermal radiation model for rocket plume base heating using the finite-volume method
Kim, Man-Yeong ; Baek, Seung-Uk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3598~3606
DOI : 10.22634/KSME-B.19126.96.36.19998
The finite volume method for radiation is applied to investigate a radiative heating of rocket base plane due to searchlight and plume emissions. Exhaust plume is assumed to absorb, emit and scatter the radiant energy isotropically as well as anisotropically, while the medium between plume boundary and base plane is cold and nonparticipating. Scattering phase function is modelled by a finite series of Legendre polynomials. After validating benchmark solution by comparison with that of previous works obtained by the Monte-Carlo method, further investigations have been done by changing such various parameters as plume cone angle, scattering albedo, scattering phase function, optical radius and nozzle exit temperature. The results show that the base plane is predominantly heated by the plume emission rather than the searchlight emission when the nozzle exit temperature is the same as that of plume.
A study on the pulsatile flow characteristics of Newtonian and non-Newtonian fluids in the bifurcated tubes
Seo, Sang-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3607~3619
DOI : 10.22634/KSME-B.19188.8.131.5207
Experimental and numerical studies for three-dimensional pulsatile flows are conducted to investigate the flow characteristics in the bifurcated tubes. Velocity measurements in experimental study were made by both Pulsed Doppler Ultrasound(PDU) machine and Laser Doppler Anemometer(LDA) system. Glycerin is used for experimental study. Experimental results are used to verify the results of the numerical simulation. Flow characteristics of Newtonian fluid and blood in the bifurcated tubes under the steady and pulsatlie flows are numerically investigated. Finite volume method is employed for three-dimensional numerical simulations. Blood is considered as a non-Newtonian fluid and the constitutive equation of blood is used for the numerical analysis. Numerical analyses are focused on the flow patterns for various branch angles ranging from 30.deg. to 90.deg. and diameter ratios such as 1.0, 0.8, and 0.6. Pulsatile flow characteristics of blood are compared with those of Newtonian fluid. Parameter effects on axial velocity, pressure and wall shear stress distribution along the bifurcated tubes are discussed in terms of the branch angle, diameter ratio, and Reynolds number.
A numerical study of the performance of a turbomolecular pump
Hwang, Yeong-Gyu ; Heo, Jung-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3620~3629
DOI : 10.22634/KSME-B.19184.108.40.20620
In the free molecular flow range, the pumping performance of a turbomolecular pump has been predicted by calculation of the transmission probability which employs the integral method and the test particle Monte-Carlo method. Also, new approximate method combining the double stage solutions, so called double-approximation, is presented here. The calculated values of transmission probability for the single stage agree quantitatively with the previous known numerical results. For a six-stage pump, the Monte-Carlo method is employed to calculate the overall transmission probability for the entire set of blade rows. When the results of the approximate method combining the single stage solutions are compared with those of the Monte-Carlo method at dimensionless blade velocity ratio C=0.4, the previous known approximate method overestimates as much as 34% than does the Monte-Carlo method. But, the new approximate method gives more accurate results, whose relative error is 10% compared to the Monte-Carlo method, than does the previous approximate method.
Experimental study of solid fuel ignition in a confined enclosure
Kim, Yeong-Gwan ; Baek, Seung-Uk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3630~3638
DOI : 10.22634/KSME-B.19220.127.116.1130
An experimental study has been conducted to explore the behaviors of the radiative ignition of polymethylmetacrylate(PMMA) in a confined enclosure such as the ignition delay time, PMMA surface temperature, the ignition location and the ignition process. In addition, the effects of hot wall orientation on the ignition delay and PMMA surface temperature were studied. When the hot wall is located at the bottom, ignition delay time is the shortest. Ignition surface temperature becomes the lowest for the hot top wall case. These are due to buoyancy effect. Since the radiative heat flux of hot wall is rather lower than laser source, the ignition is considered to be controlled by the mixing process. Therefore, the ignition location, where appropriate mixture of fuel and oxygen exists, occurs near the hot wall. The flame propagates along the hot wall where there exists sufficient oxygen.
The effect of pinched diffuser on aerodynamic performance in a centrifugal compressor
O, Jong-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3639~3648
DOI : 10.22634/KSME-B.1918.104.22.16839
The effect of 15% pinched diffuser in a centrifugal air compressor with a cascade airfoil diffuser on the aerodynamic performance is investigated using a numerical approach. The commercial CFD code for three-dimensional, turbulent, compressible flow fields is executed for various mass flow rates at a design speed which can be obtained as long as the calculation succeeds. The pinched diffuser is found to help improve the instability of flow within vaneless diffuser space, especially the reverse flow near shroud, and to change both stall/surge line and choking line to increase the surge margin. It is also found to generate more favorable increase of static pressure in diffuser region, and to increase the resulting pressure ratio and efficiency.
A method for the determination of transient flow rates from pressure measurements
Lee, Seong-Rae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3649~3654
DOI : 10.22634/KSME-B.1922.214.171.12449
A transient hydraulic flow rate computation scheme is described here so that the transient hydraulic flow rate can be determined using the dynamic pressure measurements at the ends of a straight flow line with a dynamic model of the hydraulic line. This method can be applied to determine the orifice ares of high response valve. Simulation results indicate that the method is relatively robust to realistic levels of uncertainties in the fluid properties.
Analytical solution to the conduction-dominated solidification of a binary mixture
Jeong, Jae-Dong ; Yu, Ho-Seon ; No, Seung-Tak ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3655~3665
DOI : 10.22634/KSME-B.19126.96.36.19955
An analytical solution is presented for the conduction-dominated solidification of a binary mixture in a semi-infinite medium. The present approach differs from that of other solution by these four characteristics. (1) Solid fraction is determined from the phase diagram, (2) thermophysical properties in mushy zone are weighted according to the local solid fraction, (3) non-equilibrium solidification can be simulated and (4) the cooling condition of under-eutectic temperature can be simulated. Up to now, almost all analyses are based on the assumption of constant properties in mushy zone and solid fraction linearly with temperature or length. The validation for these assumptions, however, shows that serious error is found except some special cases. The influence of microscopic model on the macroscopic temperature profile is very small and can be ignored. But the solid fraction and average solid concentration which directly influence the quality of materials are drastically changed by the microscopic models. An approximate solution using the method of weighted residuals is also introduced and shows good agreement with the analytical solution. All calculations are performed for NH
O and Al-Cu system.
Hardware temperature compensation technique for hot-wire anemometer by using photoconductive cell
Lee, Sin-Pyo ; Go, Sang-Geun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3666~3675
DOI : 10.22634/KSME-B.19188.8.131.5266
A new hardware temperature compensation method for hot-wire anemometer is investigated and an analog compensating circuit is proposed in this article. A photoconductive cell is introduced here as a variable resistor in the anemometer bridge and the linearized output of a thermistor is used to monitor the input of the photoconductive cell. In contrast with the conventional method, any type of temperature sensor can be used for compensation if once the output of thermometer varies linearly with temperature. So the present technique can diversify the compensating means from a conventional passive compensating resistance to currently available thermometers. Because the resistance of a photoconductive cell can be set precisely by adopting a stabilizing circuit whose operation is based on the integration function of the operational amplifier, the accuracy of compensation can be enhanced. As an example of linearized thermometer, thermistor sensor whose output is linearized by a series resistor was used to monitor the fluid temperature variation. Validation experiment is conducted in the temperature ranged from 30 deg. C to 60 deg. C and the velocity up to 40 m/s. It is found that the present technique can be adopted as a compensating circuit for anemometer and hot-wire type airflow meter.
A basic study on development of multiple- spark capacitor discharge igniter for lean burn engine
Lee, Sang-Jun ; Na, Seong-O ; Lee, Jong-Tae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3676~3685
DOI : 10.22634/KSME-B.19184.108.40.20676
Enhancement of the ignitability was necessary to realize the lean burn engine. The characteristics of multiple-spark capacitor discharge igniter(MSCDI) usefulness of which for lean burn was examined in constant volume combustion chamber and evaluated in spark ignition engine. Noise of MSCDI for engine was restricted by adoption of low voltage control system. It was found that the adaptability for high engine speed was remarkable. Lean limit in engine with MSCDI was extended 10% than conventional coil ignition system. Also maximum brake thermal efficiency was almost enhanced 1%.
A study of natural convection in non-Newtonian fluids induced by a vertical wavy surface
Kim, Eun-Pil ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3686~3694
DOI : 10.22634/KSME-B.19220.127.116.1186
A numerical investigation of natural convection flow along irregular vertical surfaces is reported. A transformation method is applied to the problem of natural convection under the assumption of a large Grashof number. A vertical wavy surface is used as an example to demonstrate the advantages of the transformation method, and to show the heat transfer mechanism near such surfaces. Surface non-uniformities on the boundary layer flow induced by a constant was temperature, semi-infinite surface are investigated. Also the effects of Prandtl number, flow index, and surface amplitude in Non-Newtonian fluids are discussed. When possible, the comparison of the numerical results shows a good agreement. The amplitude is proportional to the amplitude of a wavy surface. The results demonstrate that the local heat flux along a wavy surface is smaller than that of a flat surface. The frequency of the wavy surface is half that of the local heat transfer rate. The amplitude of the local Nusselt number gradually decreases downstream where the natural convection boundary layer grows thick.
Particulate Two-Phase Flow Analysis for Fouling Prediction(I)-Design of Hot Wind Tunnel and Its Performance Experiment-
Ha, Man-Yeong ; Lee, Dae-Rae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3695~3705
DOI : 10.22634/KSME-B.1918.104.22.16895
We designed the hot wind tunnel to reproduce the conditions of utility boiler and carried out its performance test, in order to investigate the particulate two-phase flow behaviour, the fouling and heat transfer characteristics to the heat exchanger. The hot wind tunnel introduces the control system to control the temperature in the test section. The particle is injected into the hot gas stream. The fouling probe (cylindrical tube) is positioned normal to the particulate gas-particle two-phase flow and cooled by the air. The temperature of gas and cooling air, and temperature in the fouling probe are measured as a function of time, giving the local and averaged heat transfer and fouling factor. The shape of particulate deposition adhered to the fouling probe is also observed.
Natural convection induced by free surface heat flux and temperature difference between left and right walls in glass melting furnace
Im, Gwang-Ok ; Lee, Gwan-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 11, 1996, Pages 3706~3713
DOI : 10.22634/KSME-B.1922.214.171.12406
A numerical study on natural convection induced by free surface heat flux and cold left and hot right walls in glass melting furnaces has been performed. A function of heat flux derived from the combustion environments of actual glass melting furnace is applied to thermal boundary condition at free surface. Fundamentally there exist two flow cells in cavity (left counterclockwise one and right clockwise one). The effects of heat flux and Rayleigh number are investigated through two-dimensional steady-state assumption. The convection strength of two flow cell located in left region continuously increases. In the mean time the strength of flow cell in right region increases and then decreases. Critical Rayleigh number in which two flow cells take place above and below show linear dependence on the free surface heat flux. To maintain the traditional flow pattern (left and right flow cells) in glass melting furnace, Rayleigh number is recommended to be below 10