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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
Editor in Chief :
Volume & Issues
Volume 22, Issue 7 - Jul 1998
Volume 22, Issue 6 - Jun 1998
Volume 22, Issue 5 - May 1998
Volume 22, Issue 4 - Mar 1998
Volume 22, Issue 3 - Mar 1998
Volume 22, Issue 2 - Feb 1998
Volume 22, Issue 1 - Jan 1998
Volume 22, Issue 10 - 00 1998
Selecting the target year
A study on flow characteristics of laminar oscillatory flows in a square-sectional
Park, Gil-Mun ; Jo, Byeong-Gi ; Bong, Tae-Geun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 139~152
DOI : 10.22634/KSME-B.1918.104.22.168
In the present study, the flow characteristics of developing laminar oscillatory flows in a square -sectional 180 deg. curved duct are investigated experimentally. The experimental study using air in a square-sectional 180 deg. curved duct is carried out to measure velocity distributions with a data acquisition and LDV (Laser Doppler Velocimetry) processing system. In this system, Rotating Machinery Resolver (RMR) and PHASE program are used to obtain the results of unsteady flows. The major flow characteristics of developing oscillatory flows are found by analyzing velocity curves, mean velocity profiles, time-averaged velocity distribution of secondary flow, wall shear stress distributions, and entrance lengths. In a lower dimensionless angular frequency, the axial velocity distribution of laminar oscillatory flow in a curved duct shows a convex shape in a central part and axial symmetry. The maximum value of wall shear stress in a lower dimensionless angular frequency is located in an outside wall, but according to increasing the dimensionless angular frequency, the maximum of wall shear stress is moved to inner wall. The entrance lengths of laminar oscillatory flows in a square-sectional 180 deg. curved duct is obtained to 90 deg. of bended angle of duct in this experimental conditions.
An experimental study on rotating stall in vaneless diffuser of a centrifugal compressor
Sin, Yu-Hwan ; Kim, Gwang-Ho ; Son, Byeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 153~161
DOI : 10.22634/KSME-B.1922.214.171.124
This study describes the results of the analysis of measured rotating stall signal in a centrifugal compressor with vaneless diffuser. Unsteady flow and rotating stall in vaneless diffuser were investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. Experiments were carried out in several impeller rotating speeds, at different radius ratios. Single hot -wire was used to study the characteristics of rotating stall. As a result, the abrupt rotating stall was detected at all measured impeller rotating speeds and the several flow coefficients which are less than 0.16. The number of the stall cell was one at all measured rotational speeds, and the rotating direction was the same as that of the impeller. As the flow rate decreased, the profile of the phase averaged radial velocity component with time changed from a sawtooth to a sine wave.
Application of sensitivity analyses in premixed combustion within a porous ceramic burner
Im, In-Gwon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 162~172
DOI : 10.22634/KSME-B.19126.96.36.199
A numerical study of premixed combustion within a porous ceramic burner (PCB) is performed to understand flame behavior with respect to various model parameters. Basic flame structure within the porous ceramic burner and species profiles such as NO and CO are examined. Sensitivity analysis of flame speed, gas and solid temperature, NO and CO emission from the burner with respect to reaction steps and various physical properties of the ceramic material is applied to find the most significant parameters in selection of porous materials for the porous ceramic burner. Effects of thermal conductivity, extinction coefficient and scattering albedo on the burner characteristics are studied through the sensitivity analysis. The results of sensitivity study reveal the order of importance in ceramic material properties to get suitable burner performance. Scattering albedo, which governs the ratio of absorbed energy by the ceramic material to total radiative energy transferred, is one of the most important parameters in the material properties since it affects the actual absorbed radiation rate and thus it largely affects the flame structure. Through the study, it is found that the sensitivity study can be used to estimate the flame behavior within the porous ceramic burner more effectively.
Optimization of inlet concentration condition for uniform film growth in a cylindrical CVD chamber
Jo, Won-Guk ; Choe, Do-Hyeong ; Kim, Mun-Eon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 173~183
DOI : 10.22634/KSME-B.19188.8.131.52
An optimization procedure to find the inlet concentration profile that yields the most uniform deposition rate in a cylindrical CVD chamber has been developed. Assuming that the chemical reaction time is negligibly small, a SIMPLE based finite-volume method is adopted to solve the fully elliptic equations for momentum, temperature, and concentration. The inlet concentration profile is expressed by a linear combination of Chebyshev polynomials and the coefficients of which are determined by the local random search technique. It is shown that the present method is very effective in improving the uniformity of the deposition rate, especially when Re is high and/or the wafer is placed close to the inlet. The optimal profiles have been obtained for various Re, Gr, and geometry combinations.
An extended analytical solution for the mixture solidification problem
Jeong, Jae-Dong ; Yu, Ho-Seon ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 184~192
DOI : 10.22634/KSME-B.19184.108.40.206
This paper deals with an extended analytical solution for the mixture solidification problem, in which temperature is inherently coupled with the solute transport due to the presence of volume contraction induced flow. A new exact solution to the energy equation accounting for the convection effect in the melt is successfully derived, which allows the present analysis to cover a high initial superheating. Difference in properties between the solid and liquid phases is rigorously incorporated into the model equations in the solid fraction weighted form. Taking advantage of linearized correction factors, a systematic and easy-to-implement algorithm for determining the solidus and liquidus positions is introduced, which proves not only to converge stably but also to be very efficient. For a specific case, the present results show excellent agreements with the existing solution. The effect of convection in the melt becomes appreciable with increasing the initial superheating. It is revealed that variable properties in the mushy region significantly affect the solidification behaviors. The present study is also capable of resolving the interaction between microsegregation and macrosegregation.
Numerical analysis of NOx formation characteristics in CH
-air jet diffusion flame
O, Chang-Bo ; Lee, Chang-Eon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 193~204
DOI : 10.22634/KSME-B.19220.127.116.11
Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymmetric 2-D CH
jet diffusion flame. Calculations were carried out twice with the
-Thermal Mechanism including
and thermal NO reactions and the
-Full Mechanism including prompt NO reactions in addition to the above
-Thermal NO mechanism. The results show that the flame structures such as flame temperature, major and minor species concentration are indifferent to respective mechanisms. The production path of Thermal NO is dominant comparing with that of Prompt NO in total NO production of pure CH
jet diffusion flame. This is because thermal NO mechanism mainly contributes to positive formation of NO in the whole flame region, but Prompt NO mechanism contributes to negative formation in the fuel rich region. In addition, 0
penetration near the nozzle outlet affects the flame structures, especially N0
Temperature and exhaust gas conversion efficiency of catalytic converters for natural gas vehicles
Choe, Byeong-Cheol ; Kim, Yeong-Gil ; Sakai, Takayuki ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 205~212
DOI : 10.22634/KSME-B.1918.104.22.168
Experiments were conducted to investigate the temperature profile and the emissions conversion efficiency of catalytic converters for natural gas vehicles. Two types of the catalyst structure and several transient engine operating conditions were used. The dual-bed catalyst effectively reduced the emissions in a transient period due to the low heat capacity of the front bed. The lanthanoid additives were effective in improving catalyst durability. When the natural gas fueled engine were operated outside of a very narrow window of excess air ratio (from 0.993 to 1.004), the HC and NOx conversion efficiency dropped off. The drop-off were especially fast on the lean side of the window.
Radiation in axisymmetric cylindrical coordinates with the modified discrete-ordinates method
Kim, Man-Yeong ; Baek, Seung-Uk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 213~220
DOI : 10.22634/KSME-B.1922.214.171.124
The conventional discrete-ordinates method (DOM) is modified and developed for the analysis of two-dimensional axisymmetric cylindrical enclosure with curved wall. The objective of the present work is to extend the capability of the conventional DOM into a general axisymmetric geometry like nozzle-shaped enclosure, by adopting the arbitrary control angle as was done in the finite-volume method (FVM), while keeping the same two-dimensional solution procedure as in the conventional DOM. The present method is validated by applying it to three different benchmark problems of axisymmetric enclosure containing absorbing, emitting and scattering medium. Results presented in this work not only support the solution accuracy, but also moderate efficiency in the numerical calculation of axisymmetric radiation problem.
Study on centerline turbulent structures of circular contraction and expansion ducts
Han,Yong-Un ; Lee, Jang-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 221~228
DOI : 10.22634/KSME-B.19126.96.36.199
In order to look into the comparative flow characteristics between a circular contraction duct and a circular expansion duct the both centerline turbulent structures have been investigated by the hot wire anemometry. Both of the contraction and the expansion have Morel type contours. Means, turbulences, and triple moments have been measured for the turbulent kinetic energy budgets along their centerlines. It is resulted that mean velocities of both have much deviated from theoretical values calculated by one-dimensional continuity considerations, and that for the same upstream condition, the expansion maintains the isotropy in general while the contraction maintains a severe anisotropy through the whole duct. The mean transport of the TKE along the expansion is willing to balance mostly with the dissipation in the TKE budgets while that along the contraction is balanced with the production in the turbulent kinetic energy equation.
Thermal and flow analysis for the optimization of a parallel flow heat exchanger
Lee, Gwan-Su ; Jeong, Ji-Wan ; Yu, Jae-Heung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 229~239
DOI : 10.22634/KSME-B.19188.8.131.52
The present paper examines the thermal and flow characteristics of a parallel flow heat exchanger and investigates the effects of the parameters on thermal performance by defining the flow nonuniformity. Thermal performance of a parallel flow heat exchanger is maximized by the optimization using Newton's searching method. The flow nonuniformity is chosen as an object function. The parameters such as the locations of separator, inlet, and outlet are expected to have a large influence on thermal performance of a parallel flow heat exchanger. The effect of these parameters are quantified by flow nonuniformity. The results show that the optimal locations of inlet and outlet are 19.73 mm and 10.9 mm, respectively. It is also shown that the heat transfer increases by 7.6% and the pressure drop decreases by 4.7%, compared to the reference model.
A method for predicting the aerodynamic performance of low-speed airfoils
Yu, Neung-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 240~252
DOI : 10.22634/KSME-B.19184.108.40.206
The purpose of this study is to develop a method for predicting the aerodynamic performance of the low speed airfoils in the 2-dimensional, steady and viscous flow. For this study, the airfoil geometry is specified by adopting the longest chord line system and by considering local surface curvature. In case of the inviscid incompressible flow, the analysis is accomplished by the linearly varying strength vortex panel method and the Karman-Tsien correction law is applied for the inviscid compressible flow analysis. The Goradia integral method is adopted for the boundary layer analysis of the laminar and turbulent flows. Viscous and inviscid solutions are converged by the Lockheed iterative calculating method using the equivalent airfoil geometry. The analysis of the separated flow is performed using the Dvorak and Maskew's method as the basic method. The wake effect is also considered by expressing its geometry using the formula of Summey and Smith when no separation occurs. The computational efficiency is verified by comparing the computational results with experimental data and by the shorter execution time.
Cooling performance of an electronic system including electronic components mounted with heat sink
No, Hong-Gu ; Lee, Jae-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 2, 1998, Pages 253~266
DOI : 10.22634/KSME-B.19220.127.116.11
A numerical study on the cooling performance for electronic components mounted with heat sink in an electronic system has been performed. The model of electronic system consisted with lower and upper modules in which the electronic components mounted with heat sink were arrayed. To find better configuration under a given fan power for effective cooling, the cases called 'No heat sink','Both heat sinks','Lower heat sinks', and 'Upper heat sinks' were tested. The results showed that the cooling performance in 'Upper heat sinks' was the best among four cases.