• Transactions of Materials Processing
• /
• v.14 no.1 s.73
• /
• pp.21-28
• /
• 2005

This paper is concerned with the quantitative effect of design parameters on a stamped part of the auto-body. The considered parameters in this paper are the blank holding force, the draw-bead force, the blank size which greatly affect the metal flow during stamping. The indicators of formability selected in this paper are failures such as tearing, wrinkling and the amount of springback. The stamping process of the front side inner member is simulated using the finite element analysis changing the design parameters. The numerical results demonstrate that the blank holding force cannot control the local metal flow during forming although it controls the overall metal flow. The modification of the initial blank size considering the punch opening line ensures the local wrinkling and reduces the amount of springback after forming. The restraining force of draw-bead controls the metal flow in the local area and reduces the amount of excess metal. It is noted that the parametric study of design parameters such as blank holding force, the blank size and the draw-bead are very important in the process design of the complicated member.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.1 s.139
• /
• pp.1-9
• /
• 2005

Waterjet propulsion is widely used to thrust high speed marine vessels in excess of 30-35 knots by virtue of the high propulsive efficiency, good maneuverability, and less cavitation. From the aspect of power loss, approximately $7-9\%$ of the total power is lost in intake duct due to the flow separation, nonuniformity, etc. Thus, detail understanding of flow phenomena occurring within intake duct is essential to reduce the power loss, as well as noise and vibration. The present work solved 30 incompressible RANS equations to provide complicated viscous flow features of intake duct. The numerical results were compared with experiments and good agreements were obtained for three jet velocity ratios.

• Journal of Hydrogen and New Energy
• /
• v.22 no.5
• /
• pp.721-727
• /
• 2011

All vanadium redox-flow battery (VRFB) has been studied actively as one of the most promising electrochemical energy storage systems for a wide rage of applications such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants at night time. In this study, carbon felt electrodes were treated by electrochemical oxidation with KOH, and the cyclic voltammetry were studied in order to investigate redox reactivity of vanadium ion species with carbon felt electrodes. Besides the effect of electrochemical oxidation on the surface chemistry of carbon felt electrodes were investigated using the X-ray photoelectron spectroscopy (XPS). After electrochemical oxidation, XPS analysis of PAN based GF20-3 carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after electrochemical oxidation. Redox reaction characteristics using cyclic voltammetry (CV) were ascertained that the electrochemical treated electrode were more reversible than the untreated electrode.

• 한국연소학회:학술대회논문집
• /
• 2006.10a
• /
• pp.299-303
• /
• 2006

From the analysis of fly ash, which contains unburned carbon, collected from the coal-fired Yong Hung power station, most particles are turned out to be hollow cenosphere and agglomerated soot particles. The sooting potential from six coals used in the plant were investigated with CPD model. The results show that the higher potential presented to Peabody, Arthur, Shenhua coals rather than other coals. It is necessary to measure the coal flow rates at each coal feeding pipe for four burner levels since they affect the extent of mixing of soot with oxidant, in turn, the oxidation rate of soot particles. The unbalance in coal flow rate was found in several coal pipes. We successfully reduced unburned carbon in ash by increasing the excess air and changing the SOFA yaw angle.

• Journal of the Korean Society of Tobacco Science
• /
• v.18 no.1
• /
• pp.92-99
• /
• 1996

A mathematical model of the pressure gradient of supercritical CO2 in a vertical tobacco bed was developed in this study. In particular, the compaction of the tobacco as a function of temperature and CO2 flow is included in the model. Downflow of CO2 (low condition is described. At velocities in excess of 0.6 cm/sec at 7$0^{\circ}C$, there is a large increase in pressure gradient for beds deeper than about 0.5 m. The proposed model offers a better understanding of operating the process using supercritical CO2.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.973-978
• /
• 2001

Numerical Analysis for liquid fuel combustion of horizontal firing boiler is performed. The mixture-fraction/PDF equilibrium chemistry model is used to predict the combustion of the vaporized fuel. P1 model for radiation effect is used. Superheater, reheater and economizer is modeled using porous with heat sink. Flow and temperature field is investigated, and distribution of thermal $NO_{x}$ and CO is investigated. Computation as the change of excess air and swirling is performed to investigate the change of thermal $NO_{x}$.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.9A
• /
• pp.762-771
• /
• 2005

In this paper, an efficient Adaptive quality-of-service (QoS) traffic control scheme with priority scheduling is proposed for the multimedia traffic transmission over wireless access networks. The objective of the proposed adaptive QoS control (AQC) scheme is to realize end-to-end QoS, to be scalable without the excess signaling process, and to adapt dynamically to the network traffic state according to traffic flow characteristics. Here, the reservation scheme can be used over the wireless access network in order to get the per-flow guarantees necessary for implementation of some kinds of multimedia applications. The AQC model is based on both differentiated service model with different lier hop behaviors and priority scheduling one. It consists of several various routers, access points, and bandwidth broker and adopts the IEEE 802.1 le wireless radio technique for wireless access interface. The AQC scheme includes queue management and packet scheduler to transmit class-based packets with different per hop behaviors (PHBs). Simulation results demonstrate effectiveness of the proposed AQC scheme.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.10a
• /
• pp.257-260
• /
• 2003

Dynamic simulation program for a smart UAV turbojet engine was developed. The transient simulation program utilized the CMP(Constant Mass flow) method and Euler integration method for integration of excess torque. The transient performance analysis was carried out by increasing from the idle to the maximum rotational speed of the gas generator. To observe engine dynamic behavior, fuel flow was monitored through a step and a ramp increase. When the fuel was increased as a step function the overshoot of the turbine inlet temperature exceeded the limit temperature.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.686-691
• /
• 2000

The flat flame made by swirling air has lots of the different characteristics according to the swirl numbers in the burner throat. Its combustion characteristics are also affected by them. In this study, the flow patterns in the flat flame burner which is no firing condition were investigated experimentally with using smoke in terms of each swirl number. Also the blow off, flame structure, temperature distribution and NO emission in the firing condition were measured at the atmosphere and combustion furnace.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.8
• /
• pp.1999-2011
• /
• 1995

Computer simulation was conducted to study performance characteristics of air-cooled condenser of a double effect absorption heat pump with variations of saturation pressures and mass flow rates of the refrigerant ; volume flow rates, relative humidities and temperatures of the air The vertically installed condenser had the staggered tube array with continuous plate fins of wavy type. When the saturation pressure of the condenser was decreased from 760 torr to 20 torr, heat transfer rates and condensing rates of refrigerant were decreased. If excess refrigerant flows in the condenser, the pressure and saturation temperature of the condenser were increased which makes the refrigerating capacity of an absorption heat pump reduced.