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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 34, Issue 12 - Dec 2010
Volume 34, Issue 11 - Nov 2010
Volume 34, Issue 10 - Oct 2010
Volume 34, Issue 9 - Sep 2010
Volume 34, Issue 8 - Aug 2010
Volume 34, Issue 7 - Jul 2010
Volume 34, Issue 6 - Jun 2010
Volume 34, Issue 5 - May 2010
Volume 34, Issue 4 - Apr 2010
Volume 34, Issue 3 - Mar 2010
Volume 34, Issue 2 - Feb 2010
Volume 34, Issue 1 - Jan 2010
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Study on the Effect of Thermal Stratification on DME/n-Butane HCCI Combustion
Lim, Ock-Taeck ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1035~1042
DOI : 10.3795/KSME-B.2010.34.12.1035
The thermal stratification effect has been thought as one of the way to avoid dramatically generating the heat from HCCI combustion. We investigate the effect of thermal stratification on HCCI combustion fueled by DME and n-Butane. The thermal stratification occurs in a combustion chamber of a rapid compression machine with premixture by buoyancy effect that is made of fuel and air. The premixture is then adiabatically compressed, and during the process, the in-cylinder gas pressure is measured and two-dimensional chemiluminescence images are prepared and analyzed. Under the thermal stratification, the LTR starting time and the HTR starting time are advanced than that of homogeneous case. Further, the LTR period and the luminosity duration under homogeneous conditions are shorter than the corresponding quantities under stratified conditions. Additionally, under stratified conditions, the brightest luminosity intensity is delayed longer than that of homogeneous condition.
Using Two-Dimensional Chemiluminescence Images to Study Inhomogeneity in Mixture Gas in the Combustion Chamber for HCCI Combustion
Lim, Ock-Taeck ; Iida, Norimasa ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1043~1050
DOI : 10.3795/KSME-B.2010.34.12.1043
Fuel stratification and thermal stratification occur in the HCCI combustion chamber on a microscopic scale. They affect the ignition and combustion processes. In this study, the effect of the inhomogeneity in the mixture gas on the HCCI combustion process was investigated. Two-dimensional chemiluminescence images were captured using a framing camera to evaluate the flame structure. DME was used as the test fuel. First, the effect of inhomogeneity in the fuel distribution in the premixture was investigated for the four-stroke optically accessible engine. Then, by comparing the combustion of the homogeneous mixture in the rapid compression machine, which does not contain any residual gas, with the combustion in the four-stroke engine, the effect of inhomogeneity in temperature due to the residual gas was analyzed. The results showed that a time lag appears spatially in combustion under inhomogeneous conditions in the four-stroke engine. The spatial variation in the combustion without the residual gas in the rapid compression machine is less than that in the combustion in the four-stroke engine.
Analyses of Size of Solidified Particles in Steam Explosions of Molten Core Material
Park, Ik-Kyu ; Kim, Jong-Hwan ; Min, Beong-Tae ; Hong, Seong-Wan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1051~1060
DOI : 10.3795/KSME-B.2010.34.12.1051
The effect of materials on fuel coolant interactions (FCIs) was analyzed on the basis of a solidified particle size response for TROI experiments.
The solidified particle size response can provide an understanding of the relationship among the initial condition, the mixing, and an explosion. Through a comparison of the size distributions of the solidified particles in the case of explosive and non-explosive FCIs, it is revealed that an explosive FCI results in the production of a large amount of fine particles and a small amount of large particles. The material effect of the size of solidified particles was analyzed using non-explosive FCIs without losing the information on the mixing. This analysis indicates that an explosive melt includes large particles that participate in the steam explosion, whereas a nonexplosive melt includes smaller particles and finer particles.
Compressibility Effect in the Axisymmetric Internal Flow Past a Microgap
Kim, Seong-Soo ; Chang, Se-Myong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1061~1069
DOI : 10.3795/KSME-B.2010.34.12.1061
In this study, a simplified axisymmetric model is proposed for the problem of compressible internal flow past a microgap. Using numerical and experimental methods, the phenomena of choked flows are observed; these flows are induced by the acceleration of subsonic flows past the narrow cross-section of an annular shape made by a microgap. The relation between mass flow rate and differential pressure is obtained, and by comparing the result with experimental results, the reliability of the numerical results is discussed. The generation of a supersonic jet flow and its diffraction are visualized by performing the numerical analysis of axisymmetric compressible Navier-Stokes equations. This investigation greatly extends the physical understanding of the axisymmetric compressible flow, which has a wide range of engineering applications, e.g., in the case of valves in automotive power systems.
Frosting Heat Transfer Characteristics of Evaporators Used for Household Refrigerators According to Fin Configuration
Lee, Moo-Yeon ; Lee, Sang-Heon ; Jung, Hae-Won ; Kim, Yong-Chan ; Park, Jae-Jung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1071~1078
DOI : 10.3795/KSME-B.2010.34.12.1071
The objective of this study is to investigate the heat transfer characteristics of evaporators that have various fin configurations and are used in household refrigerators. The frosting and defrosting characteristics of a spirally coiled circular fin-tube evaporator, a discrete-plate fin-tube evaporator, and a continuous-plate fin-tube evaporator were measured and compared. Under non-frosting conditions, the heat transfer coefficient of the spirally coiled circular fin-tube evaporator was 22.3% and 40.2% higher than the coefficients of the discrete- and continuous-plate fin-tube evaporators, respectively. Under frosting conditions, the heat transfer coefficient of the spirally coiled circular fin-tube evaporator was 27.0% and 46.3% higher than the coefficients of the discrete- and continuous-plate fin-tube evaporators, respectively. In addition, the defrosting water amount of the spirally coiled circular fin-tube evaporator was 3.2% and 9.4% lower than the amounts in the case of the discrete- and continuous-plate fin-tube evaporators, respectively.
Analytical Modeling of a Loop Heat Pipe with a Flat Evaporator by Applying Thin-Film Theory
Jung, Eui-Guk ; Boo, Joon-Hong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1079~1085
DOI : 10.3795/KSME-B.2010.34.12.1079
A steady-state analytical model was presented for a loop heat pipe (LHP) with an evaporator that has a flat geometry. On the basis of a series of reviews of the relevant literature, a sequence of calculations was proposed to predict the temperatures and pressures at each important part of the LHP: the evaporator, liquid reservoir (compensation chamber), liquid line, vapor line, and condenser. The analysis of the evaporator, which is the only part in the LHP that has a capillary structure, was emphasized. Thin-film theory is applied to account for the pressure and temperature in the region adjacent to the liquid-vapor interface in the evaporator. The present study introduced a unique method to estimate the liquid temperature at the interface. Relative freedom was assumed in the configuration of a condenser with a simplified liquid-vapor interface. Our steady-state model was validated by experimental results available in the literature. The relative error was within 3% on the absolute temperature scale, and reasonable agreement was obtained.
Single-Camera Micro-Stereo 4D-PTV
Doh, Deog-Hee ; Cho, Young-Beom ; Lee, Jae-Min ; Kim, Dong-Hyuk ; Jo, Hyo-Jae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1087~1092
DOI : 10.3795/KSME-B.2010.34.12.1087
A micro 3D-PTV system has been constructed using a single camera system. Two viewing holes were created behind the object lens of the microscopic system to construct a stereoscopic viewing image. A hybrid recursive PTV algorithm was used. A concept of epipolar line was adopted to eliminate many spurious candidates. Three-dimensional velocity vector fields were obtained by calculating the three-dimensional displacements of particles that were identified as being identical. The system consists of a laser light source (Ar-ion, 500 mW), one high-definition camera (
pixels, 500 fps), a circular plate with two viewing holes, and a host computer. The performance of the developed algorithm was tested using artificial images. The characteristic of the vector recovery ratio was investigated for the particle numbers. A micro backward-facing step channel (
) was measured using the developed measurement system. The results were in good qualitative agreement with other results.
A Study on the Thermal-Hydraulic Characteristics of Molten Salt in Minichannels of an Intermediate Heat Exchanger for a Very High Temperature Reactor (VHTR)
Jeong, Hui-Seong ; Hwang, In-Seon ; Bang, Kwang-Hyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1093~1099
DOI : 10.3795/KSME-B.2010.34.12.1093
For Very High Temperature Reactors (VHTR), the designs of the Intermediate Heat Transport Loop (IHTL) and the Intermediate Heat Exchanger (IHX) are particularly difficult because of the high-temperature operation (up to
). In this study, Flinak molten salt, a eutectic mixture of LiF, NaF, and KF (46.5:11.5:42.0 mole %) is considered as the heat transporting fluid in the IHTL. To evaluate the flow and heat transfer performance of the Flinak molten salt in small channels with hydraulic diameters in the millimeter range, a double-pipe heat exchanger was constructed using small-diameter tubes for the heat exchange between the Flinak and the gas flow. The experimental data showed that, for laminar Flinak flow, the measured friction factors were close to the 64/Re curve and the Nusselt numbers were generally between 3.66 and 4.36.
Experimental Study of Char Oxidation and Kinetic Rate in O
Kim, Song-Gon ; Lee, Cheon-Seong ; Lee, Byoung-Hwa ; Song, Ju-Hun ; Chang, Young-June ; Jeon, Chung-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1101~1109
DOI : 10.3795/KSME-B.2010.34.12.1101
We investigated the combustion rate and kinetic rate of char when burning in oxygen-enriched atmospheres with either an
bath gas in a drop tube furnace. The experiments were performed with sub-bituminous coal (Adaro) and bituminous coal (Coal valley) under atmospheric pressure conditions. Two different coals were investigated over 12 to 30 vol% oxygen and furnace temperatures of 900, 1100, and
. For both coals, the particle temperature and overall reaction rate are lower in the
bath gas. However, analysis of single-particle data shows that the surface-specific burning rate of char oxidation is similar in both gases. In addition, the kinetic rate and activation energy for each coal were similar for both gases. Generally, the particle temperature and overall reaction rate of sub-bituminous coal are higher than those of bituminous coal.
Condensation Heat Transfer and Pressure Drop in Flat Tubes with Different Aspect Ratios
Kim, Nae-Hyun ; Park, Ji-Hoon ; Cha, Sang-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1111~1119
DOI : 10.3795/KSME-B.2010.34.12.1111
In this study, condensation heat transfer coefficients of R-410A were obtained in flattened tubes made from round tubes with an inner diameter of 5.0 mm. The saturation temperature was
; the heat flux, 10 kW/
; the mass flux, 100-400 kg/
; and the quality, 0.2-0.8. The results showed that the effect of the aspect ratio on the condensation heat transfer coefficient depended on the flow pattern. For annular flow, the heat transfer coefficient increased as the aspect ratio increased. For stratified flow, however, the reverse was true: the pressure drop increased as the aspect ratio increased. Existing correlations adequately predicted the heat transfer coefficients and pressure drops of the flattened tubes.
Effects of Aromatics and T90 Temperature of Low Cetane Number Fuels on Exhaust Emissions in Low-Temperature Diesel Combustion
Han, Man-Bae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 34, issue 12, 2010, Pages 1121~1126
DOI : 10.3795/KSME-B.2010.34.12.1121
This study is to investigate the effects of aromatics and T90 for low cetane number (CN) fuels on combustion and exhaust emissions in low-temperature diesel combustion. We use a 1.9-L common rail direct injection diesel engine at 1500 rpm and 2.6 bar BMEP. Low temperature diesel combustion was achieved via a high external EGR rate and strategic injection control. The tested fuels four sets: the aromatic content was 20% (A20) or 45% (A45) and the T90 temperature was
(T340) with CN 30. Given the engine operating conditions, the T90 was the stronger factor on the ignition delay time, resulting in a longer ignition delay time for higher T90 fuels. All the fuels produced nearly zero PM because of the extension of the ignition delay time induced by the low cetane number. The aromatic content was the main factor that affected the NOx and the NOx increased with the aromatic content.