• Tribology and Lubricants
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• v.24 no.3
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• pp.133-139
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• 2008

In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. In this paper, it will be investigated the tendency of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress. Finally, the pressure distributions on the oil film of piston pin bearings will be found by two-dimensional lubrication analysis in order to help the optimum design of the bearings of piston pin. Specially, it is investigated the effects on the film pressure distribution due to the change in maximum combustion pressure.

• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.40-45
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• 2007

This study was performed to investigate the effect of various propeller tunnel shapes on the propulsion performance of a fishing boat. The propeller tunnel reduces the problem resulting from the open propeller accidentally catching the waste net and cable on the sea, as well as increasing the cruising speed. For 3 different tunnel geometries, the model test is conducted in the circular water channel, and the potential based panel method was applied to analyze the hydrodynamic characteristics of propeller. Also, both results are compared with each other to represent the difference between results of the model scale test and the potential theory. It is expected that these results could be referenced in the design of the propeller tunnel in consideration of the hydrodynamic interaction between the propeller and the tunnel.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.56.1-56.1
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• 2011

This study focus on the performance of blade with blunt airfoil which used at root region on Computational Fluid Dynamics(CFD). Based on the Phase VI had experiment by NREL, the experiment condition is also used for the performance of blade with the airfoil that trailing edge is changed. The thickness of airfoil trailing edge 1% and 5% is substituted for original airfoil. This study was progressing to calculate the pressure coefficient and torque from the effect on each airfoil according to difference of the thickness.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2423-2425
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• 2004

Mobility of an indoor wheeled robot is affected by adhesion force that is related to various floor conditions. When the adhesion force between driving wheels and the floor decreases suddenly, the robot has slip state. First of all, this paper models adhesion characteristics and slip in wheeled robot. Secondly, the paper proposes estimation method of adhesion force coefficient(AFC) according to slip velocity. In order to overcome this slip problem, optimal slip velocity must be decided for stable movement of wheeled robot. The paper proposes an anti-slip control system based on an ordinary disturbance observer, that is, the re-adhesion control is achieved by reducing the driving torque enough to give maximum adhesion force coefficient. fuzzy logic controller(FLC) is petty useful with slip through that compare fuzzy with PI control for the controller performance. These procedure is implemented using a Pioneer 2-DXE parameter.

• Tribology and Lubricants
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• v.24 no.2
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• pp.55-62
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• 2008

In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. In this paper, it will be investigated the tendency of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress. Finally, the pressure distributions on the oil film of piston pin bearings will be found by two-dimensional lubrication analysis in order to help the optimum design of the bearings of piston pin. Specially, it is investigated how the changes in combustion pressure at exhaust and intake stroke and the pressure-viscosity index effect on the film pressure distribution.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.193-196
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• 1999

This paper presents a new systematic contingency selection and screening method for transient stability. The variation of modal synchronizing torque coefficient(MSTC) is computed using eigen-sensitivity analysis of the electromechanical oscillation modes in small signal stability model and contingencies are ranked in decreasing order of the sensitivities of the MSTC(SMSTC). The relevant clusters are identified using the eigenvector or participating factor. The proposed algorithm is tested on the KEPCO system. Ranking obtained by the SMSTC is consistent with the time simulation results by PSS/E.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.4
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• pp.56-65
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• 1986

This paper theoretically analyzed the relations between the out-put braking torque and the wheel cylinder pressure in the leading-trailing drum brake for heavy duty truck as the characteristics of friction in break lining, comparing with the results derived from full-scale inertial brake dynamometer test in actual braking condition to develop reliable brake system in extensive using conditions. The main results obtained are as follows; 1) The characteristic curve representing the relations between BEF (Brake Effectiveness Factor) and Friction coefficient derived from theoretical analysis are consistent with the experimental results of dynamometer test. 2) According to the results of dynamometer test, the friction coefficient of brake lining is subject to initial brake speed and the actual using temperature in brake system.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.73-76
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• 2001

This paper presents a new systematic contingency selection, screening and ranking method for on-line transient security assessment. Transient stability of a particular generator is influenced most by fault near it. Fault at the transmission lines adjacent to the generators are selected as contingency. Two screening methods are developed using the sensitivity of modal synchronizing torque coefficient and computing an approximate critical clearing time(CCT) without time simulation. The first method, which considers only synchronizing power, may mislead in some cases since it does not consider the acceleration power. The approximate CCT method, which consider both the acceleration and deceleration power, worked well. Finally the Single Machine Equivalent(SIME) method is implemented using IPLAN of PSS/E for detailed stability analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.11
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• pp.1955-1961
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• 2007

In this paper, we propose the mathematical model for the vehicle system including running characteristics. The well defined model for a system is necessary to study and to enhance system performance. To model the dynamic properties of vehicle system, we have considered two fundamental parts. The first part is the motion equations for vehicle based on Newton's second law. The second part is the torque dynamics of the traction motor. These parts are affected by outer conditions such as adhesive coefficient, running resistance and gradient resistance. The each parts are presented by the numerical formula. To test the driving characteristics of the developed model, we performed the simulations by dynamic system simulation software, "SIMULINK" and the results are given for several conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.5
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• pp.614-621
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• 2007

The fishing boat propulsion system employing the modified stern shape and the tunnel to protect a propeller is developed to increase the cruise speed and reduce he problem resulting from the open propeller accidentally catching the waste net and able on the sea. Using 3 different tunnel types, the model test was performed in the circular water channel and the panel method based on the potential theory is applied to analyze the open water performance of the propeller. In the numerical analysis using he potential-based panel method, it calculates the hydrodynamic interaction between the propeller and the tunnel and evaluates the effect of the tunnel geometry. From the numerical and experimental results differing tunnel geometries, the propulsion efficiency is increased by the larger diameter of the inlet than the outlet of the tunnel and the smaller gap between the propeller tip and the tunnel internal surface. These results provide the information of the propeller system with the tunnel and the hydrodynamic interaction between the propeller and the tunnel.