• Tribology and Lubricants
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• 제30권5호
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• pp.291-294
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• 2014

Multiple additives can help improve the performance of generally used lubricants. These additives include MoS2, cadmium, chloride, indium, sulfide, and phosphide, which are harmful to both humans and the environment. Thus, researchers in this industry have been trying to reduce the use of these additives by finding alternatives. Nanodiamonds are one of these candidates. Nanodiamond particles are very hard, chemically stable, and highly heat-conductive. This research involved uniformly dispersing nanodiamond particles in marine engine oils via a matrix synthesis method at various concentrations (0, 0.1, 0.3, 0.5, and 1.0 wt). Friction and wear tests involved constant loads on ball-on-disk specimens, where the ball was AISI 51200 steel, the disk was AISI 1020 steel, and the sliding speed was 0.217 m/s. The lowest wear occurred at a suitable concentration of nanodiamonds (0.3 wt). However, excessive amounts of nanodiamonds caused them to act as abrasive debris because of their hardness, which increased the wear amount. The friction coefficient decreased as the nanodiamond concentration increased because their octagonal, almost spherical shape caused them to act as rolling contact elements between two surfaces.

• Carbon letters
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• 제9권4호
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• pp.316-323
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• 2008

The factors that influence ablation resistance in fiber composites are properties of the reinforced fiber and matrix, plugging quantity of fiber, geometrical arrangement, crack, pore size, and their distributions. To examine ablation resistance according to distribution of crack and pore size that exist in carbon/carbon composites, this study produced various sizes of unit cells of preforms. They were densified using high pressure impregnation and carbonization process. Reinforced fiber is PAN based carbon fiber and composites were heat-treated up to $2800^{\circ}C$. The finally acquired density of carbon/carbon composites reached more than $1.932\;g/cm^3$. The ablation test was performed by a solid propellant rocket engine. The erosion rate of samples is below 0.0286 mm/s. In conclusion, in terms of ablation properties, the higher degree of graphitization is, the more fibers that are arranged vertically to the direction of combustion flame are, and the less interface between reinforced fiber bundle and matrix is, the better ablation resistance is shown.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.415-418
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• 2008

This paper presents an innovative prototype of a new conceptual electromagnetic induction-based fluid beating appliance using voltage-fed type scries capacitor-compensated load resonant high-frequency IGBT inverter with a phase-shifted PWM and a power factor correction schemes. Its operating characteristics in steady-state are illustrated including unique features and evaluated on the basis of its computer simulation and experimental results of 10kw breadboard appliance for hot water producer and superheated steamer. The promising cost effective inverter-fed boiler appliances for electromagnetic induction-heated type fluid-heating in the pipeline systems are proposed for induction-heated boiler, super heat steamer, high temperature water producer, hot gas producer and metal catalyst heating for exhaust gas cleaning in engine, which are more suitable and acceptable for industrial, chemical, and consumer energy utilization for household and business from a practical point of view.

• 연구논문집
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• 통권25호
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• pp.193-205
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• 1995

Plasma 용사 코팅 기술은 전자산업과 정보산업의 기초인 Micro 반도체 산업의 기능성 목적으로 응용되고 있으며, 항공기 등의 첨단산업에서 디젤엔진이나 가스터빈 등 응용 범위를 점차 확대하고 있는 실정이다. 또한 첨단요소 부품에 적용하여 내마모성, 내열성, 내피로성, 내부식성 등을 부여하고 있다. 기능성 부품에 후처리하여 제품의 부가가치를 향상시킬 수 있어, Plasma 용사 코팅기술의 중요성은 날로 증대되고 있는 실정이다. 본 연구에서는 Plasma 용사 기술을 이용하여 코팅을 형성 내마모시험을 통해 국내 첨단요소 부품에 기능성 부여과 낙후된 용사 기술을 향상시키는 데 있다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.200-204
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• 2005

The sirocco fan is used to get low noise, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in sirocco fan are investigated by PIV. The experiment using PIV measurement for Test section's flow characteristics acquired velocity distribution, .Condition : when sirocco fan in automobile air controller maximum 1450RPM, and a revolution is a variation (1)950RPM, (2)1100RPM, (3)1250RPM. The agreement a experiment shows the validity of this study and the results of this study would be useful to the engineers who design for the flow systems for heating, ventilation and air conditioning.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.723-728
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• 2003

The Ejector is used to get low pressure, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in ejector are investigated by PIV and CFD. The experiment using PIV measurement for mixing pipe's flow characteristics acquired velocity distribution, kinetic energy distribution, and whirlpool . (Condition : when mixing pipe's diameter ratio is 1:1.9, and the flux is $Q_{1}=1.136{\imath}/s$, $Q_{2}=1.706{\imath}/s$, $Q_{3}=2.276{\imath}/s$. Based on the PIV and the CFD results, the flow characteristics in ejector are discussed, and it shows the validity of this study.

• Journal of Biosystems Engineering
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• 제23권2호
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• pp.135-146
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• 1998

The equation to predict the soil temprature of Pusan and Chinju city as a function of time and soil depth for the geothermal energy utilization system and agriculture was devised. The equation was $T(x,t)\;=\;Tm\;-\;To{\cdot}ExP(-{\xi}){\cdot}cos{{\omega}{\cdot}[t-to-x/(2{\cdot}{\alpha}{\cdot}{\omega})^{0.5}]}$ with the soil thermal diffusivity, ${\alpha},\;of\;0.4\;\textrm{m}^2/day,\;0.0375\;\textrm{m}^2/day$ and phase zero point, to, of 24 days, 22.4 days in Pusan and Chinju city, respectively, during ten years from 1987 to 1996. The predicted and measured soil temperatures agreed well with the coefficient of determination of 0.95 at the soil depth of 0.0, 0.5, 1.0, 3.0, 5.0 m. The maximum and minimum temperature in Pusan 3.7, $30.1^{\circ}C$ at soil surface and 14.3, $18.0^{\circ}C$ at the depth of 5.0 m. The total mean temperature of soil in Pusan and Chinju city was about 16.3, $16.0^{\circ}C$, respectively.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.237-240
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• 2002

Micro catalytic reactors are alternative propulsion device that can be used on a nano satellite. When used with a monopropellant, $H_2O_2$, a micro catalytic reactor needs only one supply system as the monopropellant reacts spontaneously on contact with catalyst and releases heat without external ignition, while separate supply lines for fuel and oxidizer are needed for a bipropellant rocket engine. Additionally, $H_2O_2$ is in liquid phase at room temperature, eliminating the burden of storage for gaseous fuel and carburetion of liquid fuel. In order to design a micro catalytic reactor, an appropriate catalyst material must be selected. Considering the safety concern in handling the monopropellants and reaction performance of catalyst, we selected hydrogen peroxide at volume concentration of 70% and perovskite redox catalyst of lantanium cobaltate doped with strondium. Perovskite catalysts are known to have superior reactivity in reduction-oxidation chemical processes. In particular, lantanium cobaltate has better performance in chemical reactions involving oxygen atom exchange than other perovskite materials. In the present study, a process to prepare perovskite type catalyst, $La_{0.8}Sr_{0.2}CoO_3$, and measurement of its propellant decomposition performance in a test reactor are described.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.248-257
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• 2016

Recently, researches on the free-piston Stirling engines(FPSEs) are actively investigated. FPSEs have merits in its light weight, simple structure, and little need for maintenance, thus becoming a promising solution for the power conversion of renewable energy and waste heat recycle. This paper presents the methodology that estimates damping coefficients using analytical models of linear and nonlinear dynamics for FPSEs, and validates the methodology by comparing with existing experimental results. The analysis model predicts an operable range of linear damping coefficients forming limit cycles by using the root locus, and time responses obtained by numerical integration determines nonlinear damping coefficients. The model predictions are compared with experimental results of the well-known FPSE B-10B. We also investigate the damping characteristics regarding heater temperatures and power piston motions.

• 소성∙가공
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• 제16권4호
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• pp.266-270
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to material characteristics, such as, thermal conductivity and high temperature flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld parameters. FE simulation is performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.