• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.97-104
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• 2007

The object of this work is to analyze the macroscopic spray performance and atomization characteristics between diesel and biodiesel fuels. In this study, the effects of mixture ratios of biodiesel fuel on the spray tip penetration, fuel injection rate, spray cone angle, and the atomization characteristics such as droplet size, droplets distribution, and spray arrival time according to the axial distance were investigated at various injection parameters. It is revealed that the injection rate is more affected by injection pressure than mixture ratio. And, the spray development process is closely matched between diesel and biodiesel fuels. However, the droplet atomization characteristics of biodiesel shows deteriorated results as the mixture ratio of biodiesel increased because of the high viscosity and density.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.252-257
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• 2005

Injection molding is a very important industrial process for the manufacturing of plastics objects. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation' orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of weld-line in injection-molded products is assessed. And the effects of fiber content and injection mold-gate conditions on the fiber orientation are also discussed.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.847-852
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• 2014

As the scaling trend becomes accelerated in process technology for cost reduction in semiconductor chip manufacturing, the requirement for shrink technology has increased. Hot Carrier Injection (HCI) degradation for I/O transistors is most concerning part when shrink. To solve this, the effective channel length (Leff) was increased using liner oxide before Light Doped Drain (LDD) implants and optimized the tilt angle to increase Leff without E-field degradation in LDD region, satisfying the HCI specification.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1121-1136
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• 2002

The flow characteristics of film coolant issuing into turbulent boundary layer developing on a convex surface have been investigated by means of flow visualization and three-dimensional velocity measurement. The Schlieren optical system with a spark light source was adopted to visualize the jet trajectory injected at 35° and 90° inclination angles. A five-hole directional pressure probe was used to measure three-dimensional mean velocity components at the injection angle of 35°. Flow visualization shows that at the 90° injection, the jet flow is greatly changed near the jet exit due to strong interaction with the crossflow. On the other hand, the balance between radial pressure gradient and centrifugal force plays an important role to govern the jet flow at the 35° injection. The velocity measurement shows that at a velocity ratio of 0.5, the curvature stabilizes downstream flow, which results in weakening of the bound vortex structure. However, the injectant flow is separated from the convex wall gradually, and the bound vortex maintains its structure far downstream at a velocity ratio of 1.98 with two pairs of counter rotating vortices.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.166-174
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• 2008

Numerical study on the impingement process and the fuel film formation of the hollow-cone fuel spray was conducted under vaporization condition, and the effect of the wall cavity angle on spray-wall impingement structure was investigated. A detailed understanding of this phenomena will help in designing injection systems and controlling the strategies to improve engine performance and exhaust emissions of the Gasoline Direct Injection (GDI) engine. The improved Abramzon model was used to model the spray vaporization process and the Gosman model was adopted for modeling of spray-wall impingement process. The calculated results of the spray-wall impingement process were compared with experimental results. The velocity field of the ambient gas, the Sauter Mean Diameter (SMD) and the generated fuel film on the wall, which are difficult to obtain by the experimental method, were also calculated and discussed. It was found that the radial distance after the wall impingement and the SMD decreased with increasing the cavity angle and the temperature.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.359-366
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• 2000

A numerical study has been performed for the 2-dimensional film cooling employed in the cooling of hot components such as gas turbines. The flow and heat transfer characteristics are numerically simulated using FLUENT software. Blowing ratios vary from 0.25 to 5.0 and coolant injection angles vary from $15^{\circ}\;to\;60^{\circ}\;in\;15^{\circ}$ increment. The result shows that, for all cases, there exists a blowing ratio which maximizes film cooling effect (measured by the distance from the slot exit to the downstream wall location at which temperature increases to 900 K) for a given injection angle. It is also observed that the film cooling effectiveness decreases when downstream wall is sunk or lifted. The simulation has been performed using both constant properties and temperature dependent variable properties. It is found that the cases with constant properties overestimate the film cooling effect considerably.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.224-237
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• 1995

An ECU(Electronic Control Unit) with 16 bit microcomputer has been developed. This system includes hardware and software for more precise control on fuel injection, ignition timing, and idle speed. This control system employs an air flow sensor of the hot wire type, a direct ignition system, an idle speed control system using a solenoid valve, and a crank angle sensor. Especially, the crank angle sensor provides two separate signals: One is the position signal(POS) which indicates 180 degree pulses per revolution, and the other is the reference signla(REF) that represents each cylinder individually. The conventional engine control system requires at least two engine revolutions in order to identify the cylinder number. However, the developed engine control system can recognize the cylinder number within a quarter of an engine revolution. Therfore, the developed engine control system has been able to control fuel injection and ignition timing more quickly and accurately, Furthermore, the number of misfire reduces during the cold start.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.1
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• pp.89-97
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• 2017

Butanol has an ability to improve the ignition quality due to its lower latent heat of vaporization; it has an advantage to reduce a volume of a fuel tank because its energy density is higher than that of ethanol. Also, butanol-diesel oil blending quality is good because butanol has an effect to prevent the phase-separation between two fuels. Even if the blended oil contains water, it can reduce the corrosion of the fuel line. Thus, it is possible to use butanol-diesel oil blended fuel in diesel engine without modification, and it may reduce the environment pollution due to NOx and particulate and the consumption of diesel oil. Therefore, some studies are being advanced whether butanol is adequate as an alternative fuel for diesel engines, and the results of the combustion and exhaust gas emission characteristics are being presented. Though the injection and spray characteristics of butanol are more important in diesel combustion, the has not yet dealt with the matter. In this study, the influence in which differences of physical properties between butanol and diesel oil may affect the injection and spray characteristics such as injection rate, penetration, spray cone angle, spray velocity and process of spray development were examined by using CRDI system, injection rate measuring device and spray visualization system. The results exhibited that the injection and macroscopic spray characteristics of two fuels were nearly the same.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.9-19
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• 2017

In this study, stator shroud injection in a single-stage transonic axial compressor is proposed. A parametric study of the effect of stator shroud injection on aerodynamic performances was conducted using the three-dimensional Reynolds-averaged Navier-Stokes equations. The curvature, length, width, and circumferential angle of the stator shroud injector and the air injection mass flow rate were selected as the test parameters. The results of the parametric study show that the aerodynamic performances of the single-stage transonic axial compressor were improved by stator shroud injection. The aerodynamic performances were the most sensitive to the injection mass flow rate. Further, the total pressure ratio and adiabatic efficiency were the maximum when the ratio of circumferential angle was 10％.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.3
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• pp.644-654
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• 2001

In this paper, an electronic control unit of the automobile engine for optimal fuel injection an spark timing control has been designed and developed. This system includes hardware and software for a precise control of fuel injection and ignition timing. Especially, the crank angle sensor provides two separate signals: One is the position signal (POS) which indicates 180 degree pulses per revolution, and the other is the reference signal (REF) that represents each cylinder individually. Consequently, the developed engine control system has been able to control fuel injection and ignition timing more quickly and accurately. Through the experiment, it has been found that the fuel injection duration and the position of MBT have been influenced by coolant temperature, air flow rate and engine speed.