• 대한기계학회논문집A
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• 제27권7호
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• pp.1138-1145
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• 2003

In this paper, a study on the dynamic behavior and lubrication characteristics of a reciprocating compression mechanism used in small refrigeration compressor is performed. In the problem formulation of the compressor dynamics, the viscous frictional force between piston and cylinder wall is considered in order to determine the coupled dynamic behaviors of piston and crankshaft. The solutions of the equations of motion of the reciprocating mechanism along with the time dependent Reynolds equations for the lubricating film between piston and cylinder wall and oil films of the journal bearings are obtained simultaneously. The hydrodynamic forces of journal bearings are calculated using finite bearing model and Gumbel boundary condition. And, a Newton-Raphson procedure was employed in solving the nonlinear equations of piston and crankshaft. The results explored the effects of design parameters on the stability and lubrication characteristics of the compression mechanism.

• 한국해양공학회지
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• 제25권2호
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• pp.127-133
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• 2011

The following Technology Report was written with respect to recent offshore technology development. This report was prepared with the purpose of suggesting recent offshore technology and upcoming visions by describing the principles of an offshore drilling operation, the NL Tensioner Cylinder Package R & D, and the general technology related to three offshore patent areas, as major contents.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1141-1151
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• 1998

An effective thermal conductivity measurement for suspensions of microparticles in oil mixture is conducted in order to evaluate the shear rate-dependence of the thermal conductivity of suspensions. Measurements are made for rotating Couette flows between two concentric cylinders. The rotating outer cylinder is immersed into a constant temperature water bath while the stationary inner cylinder is subject to a uniform heat fluff. Test fluids are made to be homogeneous suspensions, in which neutrally buoyant microparticles ($d=25{\sim}300{\mu}m$) are uniformly dispersed. The present measurements show strong shear-rate dependent thermal conductivities for the suspensions, which are higher than those at zero shear rate. The shear rate dependent thermal conductivity increases with the particle size and volume concentration.4 new model for shear rate-dependent thermal conductivity of microparticle suspensions is proposed; the correlation covers from zero shear rate value to asymptotic plateau value at moderately high shear rates.

• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.2049-2057
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• 2004

In this study, the combustion characteristics and durability of a diesel engine using emulsified fuel was investigated. Water was used in oil type emulsified fuel. In order to understand the effect of emulsified fuel in a wide range of engine running conditions, D-13 mode was selected as a test condition, and a durability test was included to understand the long-term effect of water. Combustion pressure in a cylinder, exhaust emissions, specific fuel consumption, sound level and maximum torque were measured. NOx and PM were simultaneously reduced and the specific fuel consumption was increased and decreased at low and high loads, respectively. There was no trouble and any damage on the parts of the cylinder during a 500 hour durability test.

• Journal of Advanced Marine Engineering and Technology
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• 제16권5호
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• pp.6-16
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• 1992

Since world-wide oil shock on 1970s, many large size-low speed diesel engines, instead of steam turbines, are used for the industrial electric power generating plants due to their economic advantage of low specific fuel consumption. But it is very important to control their electric power fluctuation problems for the purpose of smooth parallel operation with existing power plants. In this paper the fluctuation problem of KEPCO Nam-cheju No.1 generator driven by diesel ngine(B & W 7K 60MC, 13931x138.5RPM) is investigated with analysis of torsional vibration of which 4th harmonic component is related to its power fluctuation. The problem can be improved by modification of cylinder arrangement and flywheel position in reverse sequence, equalizing the combustion gas pressure of all cylinder and installation of torsional vibration damper enlarged 30%(Je=7287Kg.m$^{2}$) and high quality balancing of generator rotor.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.369-378
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• 1999

This paper presents position control of an electro-hydraulic servo system whoch is operated by four 2-2way high speed on-off valves with either PWM PID control method or sliding mode control method, The advantages of using high speed on-off valves instead of electo-hydraulic servo valves or electro-hydraulic proportional valves are low price robustness for oil contamination and direct control without a D/A converter. The system consists of load cylinder inertia car potentiometer and external load cylinder. The experiments were carried out under several conditions and the results were compared. As a result the sliding mode method has shown good control performance and the robust and stable positioning of the elector-hydraulic servo system can be achieved accurately.

• 동력기계공학회지
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• 제19권6호
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• pp.54-59
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• 2015

This paper is a numerical study on the correlation of leakage by the variation of operating temperature and orifice diameter applying to hydrostatic bearing in hydraulic actuator. Compared with Brackbill and Kandlikar experimental paper to verify the validity of the numerical analysis technique of the present study, we derive the result that the results of experiments and numerical analysis to match very well. CFD analysis program were analyzed using a commercial code FLUENT V14.5. Inlet and outlet, were applied pressure conditions, the main variables of the analysis is temperature and the orifice inner diameter. The analysis results, pressure value has decreased as the oil temperature and the orifice diameter increases.

• 대한기계학회논문집B
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• 제30권9호
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• pp.898-904
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• 2006

A new method measuring thermal conductivity of fluids is proposed in this research. It is based on the steady state heat transfer from a hot central cylinder to a cold outer cylinder located concentrically. This method guarantees more stable measurement than conventional THM(transient hot-wire method) due to its simplicity of theoretical principle. Measurements was made for the three nanofluid samples with different particle concentration of pure, 2% and 4%. Nanofluids are made by mixing the pure transformer oil with AlN nano particles. Design of the sensor module and experimental procedures are explained and comparison of the measuring data between present method and THM was made in detail.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.199-208
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• 2017

We perform an experiment on lacquer formation with simple test device. The anti-lacquer is one of important issues to increase durability, and to improve performance in the engines because the lacquer formation cause sticking of fuel injection pump, scuffing of cylinder liners, and increase of lubricant oil consumption in the marine diesel engines. We suggest this simple test in order to save enormous experimental cost in marine diesel engines, and in order to have ease in performing the various tests. The influences of the Base Number (BN) of lubricant oils and the sulfur content of fuel oils in the formation of lacquer are investigated. In order to investigate physical and chemical properties of lacquer, we perform a variety of tests such as, visual inspection, EDS. In addition, we investigate adhesion of lacquer by pull-off test quantitatively, and perform dissolution test with dilute sulfuric acid.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1997년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.5-5
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• 1997

Rapidly-solidified P/M aluminium alloys for automobile and home appliance industries were developed. Rapidly-solidification made it possible to refine microstructures and to expand the range of alloy composition. For example, Al-Si alloys containing transition metal have lower thermal expansion coefficient, more excellent wear resistance, higher strength, and better machinability than those of conventional aluminium alloys. Therefore, in Japan, the technologies on powder-extrusion and powder-forging of aluminium alloy powders are developed for fifteen years, and applied to several parts, such as cylinder liners of motor cycle engines, rotors and vanes of compressors for car air conditioner, oil pump rotor for racing car, and so on. In this presentation, applications for automobile are mentioned. In particular, cylinder liners made of particle-dispersed composites with fine alumina and graphite are in detail described.