• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.217-218
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• 2009

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.105-106
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• 2012

This study is numerical analysis about optimal conditions of GDICI (gasoline direct injection compression ignition) engine operation using intake preheating. Numerical modeling was performed by using the KIVA-3V Release2 code integrated Chemkin chemistry solver II. For validation of numerical model, experiments were performed on a single-cylinder engine. Throughout the numerical simulations under variable conditions, the ranges of optimal conditions were found.

• Korea-Australia Rheology Journal
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• v.20 no.2
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• pp.79-88
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• 2008

In this study, we focus on the improvement of the filling efficiency in injection molding by application of ultrasonic vibration. While studies about the filling efficiency of typical filling processes in the injection molding have been widely performed, there have been only few studies about the filling efficiency of an ultrasonic process. The effect of the ultrasonic vibration is an important process condition, which influences the flow characteristics of polymer melt. This new condition even affects well-known injection conditions such as cavity pressure, injection temperature and mold temperature. For this study, we carried out a numerical analysis by appropriate modeling and analysis of the ultrasonic process in the filling process. To verify this numerical analysis, we compared the numerical results with the experimental data. Also, we analyzed the filling process in a thin cavity using this numerical analysis. To understand the flow characteristics of polymer melt in the ultrasonic process, we substituted real and complex vibration conditions with simplified and classified conditions according to the position of vibrating cavity surfaces and the phase difference between two opposing cavity surfaces. We also introduced MFR (melt flow ratio) as a new index to estimate the filling efficiency in the ultrasonic process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1323-1330
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• 2000

Recently, injection molding process became more popular than ever to produce large quantities of high precision products or optical products. Especially, optical disk that was made by injection mol ding process has been used for many years as a music play media or computer sub-device. The density of data in disk media has been increased continuously. But those optical disks can cause sensorial problems because of high birefringence or deformation from the residual stresses in the media. Therefore, it is necessary to study the effects of various process conditions on the final bireffingence structure in injection-molded disks for producing precision injection-molded products. In the present paper we have focussed on the effect of holding and compression pressures on the optical anisotropy remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle. The effect of holding pressure was found to form the inner two bireffingence peaks. But the effect of compression pressure on the bireffingence distribution was found to make the uniform distribution near the center in the gapwise direction. Finally, the value of the birefringence near the wall decreased as the mold temperature increased.

• Geomechanics and Engineering
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• v.13 no.1
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• pp.1-23
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• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.210-217
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• 2017

A gasoline direct injection engine has an intake air temperature can be lowered by the fuel vaporization in the combustion chamber increase the volume efficiency is high compression ratio. Therefore, study for injection rate and characteristics which influence mixture formation in combustion chamber is important. Movement of the injector needle has a direct effect on the injection of the fuel, such as formation of cavitation, the fuel injection rate, etc. Therefore, recent studies on the dynamic characteristics of the injector considering the movement of the needle have been reported, but it takes a lot of time and cost to experimentally confirm the movement of the needle inside the injector. In this study, AMESim, a commercial 1-D code, and Star-CCM+, a 3-D CFD code, were used to predict the dynamic performance of the injector with needle motion. In order to predict the movement of the needle under the high pressure, the result of the surface pressure distribution according to the movement of the needle was derived by using the morphing technique of flow analysis. In addition, we predicted the injection rate of the injector considering the movement of the needle in conjunction with the 1-D code. The injection rate of the injector was measured by the BOSCH's method and the results were similar to those of the simulation results. This method can predict the injection rate and injection characteristics and this result is expected to be used to predict the performance of gasoline direct injection engines with low cost and time in the future.

• Journal of Korea Foundry Society
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• v.14 no.6
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• pp.576-589
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• 1994

Water modeling experiments and computer simulation for the predictions of defects of die castings are very important to produce high quality castings with less cost. The relation between the variable air vent system and the characteristics of the fluid flow in the die cavity is studied by using water modeling tests, which give ideas on reasonable designing of die cavity, vent arrangement and gating system. In order to test the water modeling, injection is done by using water containing NaCl. Flow behaviors in cavities are visualized by high speed camera and video tape recorder, and local filling time is measured with electrode sensors. Special attention is paid to the configuration of die cavity. Simulated results by computer are examined and compared with the results of water modeling experiments. There are close correlations between the simulated results and water modeling ones.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.954-957
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• 2002

The objective of design process modeling is a systematic support of rapid redesign process fur a modified input data. The design process modeling is realized by storing key parameters or geometric entities used in the intermediate design steps and reusing them for change of the designed parts or assemblies according to the modified input. In this paper, we adopted and implemented the design process modeling approach to our injection mold design system developed based on the Unigraphics system. It was proved that the productivity of mold redesign process is raised highly by introducing the design process modeling technique mold design system.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.15-24
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• 2013

Numerical studies were conducted to investigate the internal flow field and combustion characteristics of DISI engine with methanol blended in gasoline. Dual injection was applied and the characteristics were compared to single injection strategy. The amount of the fuel injection was corresponded to air-fuel ratio of each fuel for complete combustion. The preforming model in this study, software STAR-CD was employed for both modeling and solving. The operating speed condition were at 4000 rpm/WOT (Wide open throttle) where the engine was fully warmed. The results of single injection with M28 showed that the uniformity, equivalence ratio, in-cylinder pressure and temperature increased comparing to gasoline (M0). When dual injection was applied, there was no significant change in uniformity and equivalence ratio but the in-cylinder pressure and temperature increased. When M28 fuel and single injection was applied, the CO (Carbon monoxide) and NO (Nitrogen oxides) emission inside the combustion chamber increased approximately 36%, 9% comparing with benchmarking case in cylinder prior to TWC (Three Way Catalytic converter). When dual stage injection was applied, both CO and NO emission amount increased.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.43.3-43.3
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• 2018

We develop a model for broadband spectral energy distribution (SED) of Pulsar Wind Nebulae (PWNe). The model assumes that electrons/positrons in the pulsar wind are injected into and stochastically accelerated in the pulsar termination shock. We consider two scenarios: a stationary one-zone case and a time-evolving multi-zone case. In the latter scenario, flow properties in the PWNe (magnetic field, bulk speed) are modeled to vary in time and space. We apply the model to the broadband SED of the pulsar wind nebula 3C 58. From the modeling, we find that a broken power-law injection is required with the maximum electron energy of ~200 TeV.