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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 27, Issue 12 - Dec 2003
Volume 27, Issue 11 - Nov 2003
Volume 27, Issue 10 - Oct 2003
Volume 27, Issue 9 - Sep 2003
Volume 27, Issue 8 - Aug 2003
Volume 27, Issue 7 - Jul 2003
Volume 27, Issue 6 - Jun 2003
Volume 27, Issue 5 - May 2003
Volume 27, Issue 4 - Apr 2003
Volume 27, Issue 3 - Mar 2003
Volume 27, Issue 2 - Feb 2003
Volume 27, Issue 1 - Jan 2003
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Performance Assessment of Turbulence Models for the Prediction of Tip Leakage Flow in an Axial-Flow Turbomachinery
Lee, Gong-Hee ; Baek, Je-Hyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1655~1666
DOI : 10.3795/KSME-B.2003.27.12.1655
It is experimentally well-known that high anisotropies of the turbulent flow field are dominant inside the tip leakage vortex, which is attributable to a substantial proportion of the total loss and constitutes one of the dominant mechanisms of the noise generation. This anisotropic nature of turbulence invalidates the use of the conventional isotropic eddy viscosity turbulence models based on the Boussinesq assumption. In this study, to check whether an anisotropic turbulence model is superior to the isotropic ones or not, the results obtained from the steady-state Reynolds averaged Navier-Stokes simulations based on the RNG k-
model and the Reynolds stress model (RSM) are compared with experimental data for two test cases: a linear compressor cascade and a forward-swept axial-flow fan. Through this comparative study of turbulence models, it is clearly shown that the RSM, which can express the production term and body-force term induced by system rotation without introducing any modeling, should be used to predict quantitatively the complex tip leakage flow, especially in the rotating environment.
The Study on the Two-Phase Flow in the Microchannel Using DSMC(Direct Simulation Monte Carlo) Method
Lee, Jin-Ho ; Ryu, Dong-Hun ; Lee, Tae-Hong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1667~1672
DOI : 10.3795/KSME-B.2003.27.12.1667
In contrast to the high demand for MEMS devices, microflow analysis is not feasible even for single-phase flow with conventional Navier-Stokes equation because of non-continuum effect when characteristic dimension is comparable with local mean free path. DSMC is one of particle based DNS(Direct Numerical Simulation) methods that uses no continuum assumption. In this paper, gas flow in microchannel is studied using DSMC. Interfacial shear and flow characteristics are observed and compared with the results of gas flow that is in contact with liquid case and solid wall case. The simulation is limited to the case of equilibrium steady state and evaporation/condensation coefficient is assumed to be the same and unity. System temperature remains constant and the interfacial shear appears to be small compared to the result with solid wall. This is because particles evaporated and reflected from the liquid surface form high density layer near the interface with liquid flow.
Development of Ejector System for Chemical Lasers Operating (I) - Design Parameter Study of Supersonic Ejector for Chemical Lasers Operating -
Kim, Se-Hoon ; Kwon, Se-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1673~1680
DOI : 10.3795/KSME-B.2003.27.12.1673
It is essential to operate chemical lasers with supersonic ejector system as the laser output power goes up. In this research, ejector design parameter study was carried out for optimal ejector design through understanding the ejector characteristics and design requirements for chemical lasers operating. Designed ejector was 3D annular type with 2
-throat geometry and pressurized air was used for primary flow. Ejector design was carried out with two steps, quasi-1D gas dynamics was used for first design and commercial code was used to verify the first design. In this study, to get the effect of ejector geometry on its performance, three cases of primary nozzle area ratio and 2
-throat cross sectional area and two cases of 2
-throat L/D ratio experiments were carried out. Primary and secondary pressures were measured to get the mass flow rate ratio, minimum secondary pressure, ejector starting pressure and unstarting pressure at every case. In the result, better performance than design level was shown and optimal ejector design method for chemical lasers was obtained.
Evaluation of Two-Equation Turbulence Models with Surface Roughness Effect
Yoon, Joon-Yong ; Chun, Jung-Min ; Kang, Seung-Kyu ; Byun, Sung-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1681~1690
DOI : 10.3795/KSME-B.2003.27.12.1681
The effect of roughness is a change in the velocity and turbulence distributions near the surface. Turbulence models with surface roughness effect are applied to the fully developed flow in a two-dimensional, rough wall channel. Modified wall function model, low-Reynolds number k-
model, and k-
model are selected for comparison. In order to make a fair comparison, the calculation results are compared with the experimental data. The modified wall function model and the low-Reynolds number k-
model require further refinement, while the k-
model of Wilcox performs remarkably well over a wide range of roughness values.
A Study on Effects of Exhaust Emissions with Oxygenated Fuel(DGM) and EGR Method in a Diesel Engine
Choi, Seung-Hun ; Oh, Young-Taig ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1691~1698
DOI : 10.3795/KSME-B.2003.27.12.1691
In this paper, the combination effects of oxygen component in fuel and exhaust gas recirculation on the exhaust emissions have been investigated for a direct injection diesel engine. It is a kind of effective oxygenated fuel of diether group that the smoke emission of DGM(diethylene glycol dimethyl ether) blended fuel is reduced remarkably compared with commercial diesel fuel, that is, it can supply oxygen component sufficiently at higher loads and speeds in diesel engine. But, NOx emission of oxygenated fuel was increased compared with commercial diesel fuel. Also, the effects of exhaust gas recirculation(EGR) on the characteristics of NOx emission has been investigated. It was found that simultaneous reduction of smoke and NOx was achieved with oxygenated fuel(DGM 5vol-%) and cooled EGR method(10∼15%).
An Experimental Study on the Influential Factors of Flow Measurement with Coriolis Mass Flowmeter
Lim, Ki-Won ; Lee, Woan-Kyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1699~1707
DOI : 10.3795/KSME-B.2003.27.12.1699
Coriolis mass flowmeter(CMF), which can measure the mass flow directly, is getting rapid attention for the industrial and custody transfer purpose. In order to study the characteristics and the applicability of CMF, it is tested with the national flow standard system. Two types of sensing tube, U-type and straight type, are employed in the test. Water, spindle oil and viscosity Standard Reference Material whose viscosities are 1, 20 and, 67
/s, respectively, are studied. It is shown that the linearity of CMF is getting deteriorated as the fluid viscosity increases, which is due to the zero drift and the relaxation time of the fluid. To test its applicability in the case of high pressured gas, it is calibrated using compressed air, It shows 1∼l.6 % deviations compared to the calibration results using water. It concludes that the fluid velocity in CMF should be lower than the sonic velocity. In addition, the effects of the vibration from the pipeline and pump on CMF as well as the long term stability are studied.
Influence of Unsteady Wake on Turbulent Separated Flows over a Backward-Facing Step
Chun, Se-Jong ; Sung, Hyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1708~1715
DOI : 10.3795/KSME-B.2003.27.12.1708
An experimental study was made of turbulent separated and reattaching flow over a backward-facing step, where unsteady wake was generated by a spoked-wheel type wake generator with cylindrical rods in front of the separated flow. The influence of unsteady wake was scrutinized in terms of the rotating speed of the wake generator (0
0.4). A conditional averaging technique in corporation with SBF was employed to elucidate the influence of the unsteady wake on the large-scale vortical structures of the separated flow. Special attention was made during two-dimensional measurements of wall-pressure with or without unsteady wake. The wall-pressure fluctuations were used to predict dipole sound source by Curie`s integral formula. It was found that the reduction of the dipole sound source was due to the reduction of turbulent kinetic energy by unsteady wake in the recirculation region.n.
Three Component Velocity Field Measurements of Turbulent Wake behind a Marine Propeller Using a Stereoscopic PIV Technique
Lee, Sang-Joon ; Paik, Nu-Geun ; Yoon, Jong-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1716~1723
DOI : 10.3795/KSME-B.2003.27.12.1716
A stereoscopic PIV(Particle Image Velocimetry) technique was employed to measure the 3 dimensional flow structure of turbulent wake behind a marine propeller with 5 blades. The out-of-plane velocity component was determined using two CCD cameras with the angular displacement configuration. Four hundred instantaneous velocity fields were measured for each of four different blade phases and ensemble averaged to investigate the spatial evolution of the propeller wake in the near-wake region from the trailing edge to one propeller diameter(D) downstream. The phase-averaged velocity fields show the potential wake and the viscous wake developed along the blade surfaces. Tip vortices were generated periodically and the slipstream contraction occurs in the near-wake region. The out-of-plane velocity component and strain rate have large values at the locations of tip and trailing vortices. As the flow goes downstream, the turbulence intensity, the strength of tip vortices and the magnitude of out-of-plane velocity component at trailing vortices are decreased due to viscous dissipation, turbulence diffusion and blade-to-blade interaction.
Assessment of Explicit Algebraic Stress/Heat-Flux Models for Reduction of Heat Transfer in a Vertical Pipe with Intense Heating
Baek, Seong-Gu ; Park, Seung-O ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1724~1733
DOI : 10.3795/KSME-B.2003.27.12.1724
This paper assesses the prediction performance of explicit algebraic stress and heat-flux models for reduction of heat transfer coefficient in a strongly-heated vertical tube. Two explicit algebraic stress models and four explicit algebraic heat-flux models are selected for assessment. Eight combinations of explicit algebraic stress and heat-flux models are used in predicting the turbulent gas flows with intense heating, which yields the significant property-variation. The results showed that the two combinations of GS-AKN and WJ-mAKN predicted the Nusselt number and the axial wall temperature variations well and that the predictions of Nusselt number with WJ-combinations spread in a wider range than those with Gs-combinations. WJ is the explicit algebraic stress model of Wallin and Johansson and GS is the model of Gatski and Speziale and that AKN is the explicit heat-flux model of Abe, Kondoh and Nagano and mAKN is the modified AKN.
Generation of Nano/Submicron Particles Using an Electrically Heated Tube Furnace
Ji, Jun-Ho ; Pae, Yang-Il ; Hwang, Jung-Ho ; Bae, Gwi-Nam ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1734~1743
DOI : 10.3795/KSME-B.2003.27.12.1734
Aerosol generator using an electrically heated tube furnace is a stable apparatus to supply nanometer sized aerosols by using the evaporation and condensation processes. Using this method, we can generate highly concentrated polydisperse aerosols with relatively narrow size distribution. In this work, characteristics of particle size distribution, generated from a tube furnace, were experimentally investigated. We evaluated effects of several operation parameters on particle generation: temperature in the tube furnace, air flow rates through the tube, size of boat containing solid sodium chloride(NaCl). As the temperature increased, the geometric mean diameter increased and the total number concentration also increased. Dilution with air affected the size distribution of the particles due to coagulation. A smaller sized boat, which has small surface area to contact with air, brings smaller particles of narrow size distribution in comparison of that of a larger boat. Finally, we changed the electrical mobility diameter of aggregate sodium chloride particles by varying relative humidity of dilution air, and obtained non-aggregate sodium chloride particles, which are easy to generate exact monodisperse particles.
Comparison of GDI Spray Prediction by Hybrid Models
Kang, Dong-Wan ; Hwang, Chul-Soon ; Kim, Duck-Jool ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1744~1749
DOI : 10.3795/KSME-B.2003.27.12.1744
The purpose of this study is to obtain the information about the development process of GDI spray. To acquire the characteristics of GDI spray, the computational study of hollow cone spray for high-pressure swirl injectors was performed. Several hybrid models using the modified KIVA code have been introduced and compared. WB model and LISA model were used for the primary breakup, and DDB and APTAB models were used for secondary breakup. To compare with the calculated results, the experimental results such as cross-sectional images and SMD distribution were acquired by laser Mie scattering technique and Phase Doppler Analyzer respectively. The results show that LISA+APTAB hybrid model has the best prediction for spray formation process.
Flow Measurements and Performance Analysis using a 5-Hole Pitot Tube and a Rotating Hot-Wire Probe in an Axial Flow Fan
Jang, Choon-Man ; Kim, Kwang-Yong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1750~1757
DOI : 10.3795/KSME-B.2003.27.12.1750
This paper describes the flow measurements inside the blade passage of an axial flow fan by using a rotating hot-wire probe sensor from a relative flame of reference fixed to the rotor blades. The validity of fan rotor designed by a streamline curvature equation was performed by the measurement of the three-dimensional flow upstream and downstream of the fan rotor using a 5-hole pitot tube. The vortical flow structure near the rotor tip can be clearly observed by the measurements of a relative velocity and its fluctuation on quasi-orthogonal planes to a tip leakage vortex. Larger vortical flow, which results in higher blockage in the main flow, is formed according to decrease a flow rate. The vortical flow spreads out to the 30 percent span from the rotor tip at near stall condition. In the design operating condition, the tip leakage vortex is moved downstream while the center of the vortex keeps constant in the spanwise direction. Detailed characteristics of a velocity fluctuation with relation to the vortex were also analyzed.
Uncertainty Assessment Using Monte Carlo Simulation in Gas Flow Measurement
Lee, Dae-Sung ; Yang, In-Young ; Kim, Chun-Taek ; Yang, Soo-Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1758~1765
DOI : 10.3795/KSME-B.2003.27.12.1758
Monte Carlo simulation(MC) method was used as an uncertainty assessment tool for gas flow measurement in this paper. Uncertainty sources for gas flow measurement were analyzed, and probability distribution characteristics of each source were discussed. Detailed MC methodology was described including the effect of the number of simulation. The uncertainty result was compared with that of the conventional sensitivity coefficient method, and it was revealed that the results were different from each other for this particular gas flow measurement case of which the modelling equation was nonlinear. The MC was comparatively simple, convenient and accurate as an uncertainty assessment method, especially in cases of complex, nonlinear measurement modelling equations. It was noted that the uncertainty assessment method should be selected carefully according to the mathematical characteristics of the measurement.
Calibration and Uncertainty Measurement of Differential Mobility Analyzer Using 100 nm NIST SRM 1963
Lee, Snag-Jin ; Ahn, Jin-Hong ; Ahn, Kang-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1766~1771
DOI : 10.3795/KSME-B.2003.27.12.1766
House made differential mobility analyzer(DMA) is calibrated with NIST SRM 1691(300 nm PSL). Then the particle size and uncertainty for differential mobility analyzer(DMA) using the NIST SRM 1963(100 nm PSL). In result, calibration of prototype DMA is measured using 300 nm NIST SRM 1691, then sheath air flow was corrected 126.67 ㎤/s. Corrected sheath air flow is used in uncertainty measurement of prototype DMA. Uncertainty analysis is performed using NIST SRM 1963(100 nm PSL). The experimental result shows that NIST SRM 1963 is measured as 102.17 nm with a type A uncertainty of 0.33 nm.
A Study on the Removal of Slagging and Fouling for an Optimal Operation of Power Utility Boilers
Yook, Sim-Kyun ; Kim, Sung-Ho ; Lee, Byeong-Eun ; Lee, Sang-Ryong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 27, issue 12, 2003, Pages 1772~1780
DOI : 10.3795/KSME-B.2003.27.12.1772
An optimal soot blowing system has been developed for an optimal operation of power utility boilers by both minimization of the use of steam and the number of soot blowers worked during soot blowing. Traditionally, the soot blowing system has been operated manually by operators. However, it causes the reduction of power and thermal performance degradation because all soot blowers installed in the plant should be worked simultaneously even there are lots of tubes those are not contaminated by slagging or fouling. Heat transfer area is divided into four groups, furnace, convection area including superheater, reheater and economizer, and air preheater in the present study. The condition of cleanness of the tubes is calculated by several parameters obtained by sensors. Then, a part of soot blowers works automatically where boiler tubes are contaminated. This system has been applied in a practical power plant. Therefore, comparison has been done between this system and manual operation and the results are discussed.