• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.297-299
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• 2014

Petroleum coke has high heating value and low price. Due to the steadily increasing demand for heavy oil processing, the production volume of petroleum coke tends to be expanded. The high availability and low price of petroleum coke have been strongly considered as candidate fuel for power generation facilities. However the high carbon content, high sulfur content and nitrogen content of petroleum fuel are known to produce relatively large quantity of CO2, high NOx and SO2 emission. In this work, a series of numerical simulations have been carried out in order to investigate the effects of swirl flow intensity on combustion furnace, which is most important operating condition. Results show that the temperature distribution was spatially uniform at about 1600K but high temperature region are located quite differently depending on swirl number. In addition, numerical temperature data was compared with experimental temperature data and its temperature difference shows less than 10%. On the other hand, discrepancy between numerical and experimental emission data were slightly large with necessities of improved emission model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.2962-2964
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• 2005

Magneto-Rheological (MR) fluid is suspension of fine magnetic particles in a liquid carrier such as silicon oil or water. MR fluid exhibits solid-like mechanical behavior into chain or clusters with high yield stress when magnetic field is applied to the particles. The response of MR fluids is very quick and reversible after removal of the field. MR Fluids have high yield stress (up to 5kPs) and operate in low voltage power supply. Recently, MR damper using MR fluids was open used in vibration control system such as structural devices, seat vibration controllers and helicopter rotor systems, but it is too big in size and heavy. Therefore, it is not appreciate to rehabilitation devices such as prosthetic limbs.

• 한국가스학회지
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• 제22권4호
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• pp.39-48
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• 2018

가스리프트(gas lift) 설계 영향인자인 오일 조성과 주입가스 조성에 따라 해저 오일 저류층(offshore oil reservoir) 내 가스리프트 최적 설계를 수행하였다. 이를 위해 오일의 API 비중에 따라 구축된 저류층 모델을 이용하여 생산 시뮬레이션을 수행하였다. 저류층의 지속적인 생산성 감소 시, 가스리프트 적용에 의한 오일 생산증진효과가 크게 나타남을 확인하였다. 생산정 모델을 이용하여 가스리프트 반응곡선을 분석한 결과, 오일의 API 비중이 감소하고 주입가스의 비중이 증가할수록 생산량 증진에 필요한 주입 가스량이 높게 산출되었다. 다중밸브를 이용하여 가스리프트 최적 설계를 수행하였으며, 단일밸브 설계와 비교했을 때 가스 주입심도 감소로 인해 상대적으로 낮은 주입압력으로도 가스리프트 공법 운영이 가능하였다. 저류층 모델과 생산정 모델을 연계하여 가스리프트 적용에 따른 오일 생산증진을 분석한 결과, API 비중이 낮은 중질유 저류층에 천연가스를 주입했을 때 가스리프트에 의한 생산효율이 극대화될 수 있다.

• 자원환경지질
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• 제42권5호
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• pp.427-434
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• 2009

유류 및 중금속으로 오염된 토양에서 Pb 및 Cd에 내성을 갖는 미생물을 분리하여 미생물 내 중금속 흡착 특성을 조사하였다. 분리한 토착미생물의 Pb 및 Cd의 흡착특성과 흡착에 영향을 미치는 요인 중에 생장단계, 중금속 농도, 생물량, pH, 온도에 따른 영향을 비교하였다. 또한 흡착등온식을 적용하여 중금속의 흡착용량과 흡착강도를 알아보았다. 낮은 중금속 초기 농도와 높은 생물량에서 높은 중금속 제거 효율을 가지며 중금속 마다 다른 흡착 효율을 보여 주었다. 흡착 효율은 미생물 생장 말기, pH 5~9 조건에서 최적의 효율을 나타내었으나, 25~$35^{\circ}C$에서 온도 변화에 따른 영향은 미미하였다. 생물흡착 과정을 Langmuir 등온 흡착식에 적용하면, 이론적 최대 흡착량은 Pb와 Cd에 대해서 각각 62.11과 192.31 mg/g로 나타났고, $R^2$가 0.71과 0.98로 계산되었다. Cd는 세포 표면의 단일 층에 단분자 흡착에 의한 생물흡착이 진행되었으나, Pb는 미생물 대사 작용을 통한 세포 내로의 축적 작용과 미생물 내 음이온과의 반응에 의한 침전물 형성작용 둥을 통하여 생물흡착이 진행된 것으로 판단된다.

• 한국응용과학기술학회지
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• 제32권2호
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• pp.281-289
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• 2015

본 연구는 폴리프로필렌(PP) 수지의 Co 및 Mo 촉매에 의한 반응시간과 농도변화에 따른 저온열분해 액화특성을 파악하고자 회분식 반응기를 이용하여 특정 온도(425, 450, $475^{\circ}C$)에서의 전환율을 측정하였다. 열분해 시간은 20~80분으로 설정하였고 생성물은 산업통상자원부에서 고시한 증류성상 온도에 따라 가스, 가솔린, 등유, 경유, 중유로 분류하였다. 그리고 $450^{\circ}C$ 반응온도에서 촉매 사용에 따른 전환율은 모든 반응시간에 있어 Mo 촉매 > Co 촉매 > 무촉매 순이었다. Co 및 Mo 촉매 농도별 PP 전환율 및 열분해 생성물 수율은 Co:Mo=50:50 혼합시 가장 우수한 것으로 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.744-752
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• 2007

Recently a fuel oil of the diesel engine in the ship is being changed with low quality as the oil price is higher more and more. Therefore the wear and corrosion in all parts of the engine like cylinder liner ring groove of piston crown, spindle and seat ring of exhaust valve are increased with using of heavy oil of low quality In particular the degree of wear and corrosion in between valve spindle and seat ring are more serious compared to the other parts of the engine due to operating in severe environment such as the high temperature of exhaust gas and repeating impact. Thus the repair weld to the valve spindle and seat ring is a unique method to prolong the life of the exhaust valve in an economical point of view In this study. corrosion property of both weld metal zone and base metal was investigated with some electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram and polarization resistance etc. in 5% $H_2SO_4$ solution. in the case of being welded with some welding methods and welding materials to the exhaust valve specimen as the base metal. In all cases. the values of hardness of the weld metal zone were more high than that of the base metal. And their corrosion resistance were also superior to the base metal. The weld metal of A2F(AC SMAW: 2 pass welding with foreign electrode) showed a relatively good results to the corrosion resistance as well as the hardness compared to the ether welding methods and welding materials. Moreover it indicated that hardness of the weld metal by the domestic electrode was considerably high compared to that of the foreign electrode.

• Journal of Advanced Marine Engineering and Technology
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• 제39권5호
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• pp.542-547
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• 2015

Since the oil price has been significantly jumped for several years, a heavy oil of low quality has been mainly used in the diesel engine of the merchant ship. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 625 filler metal were welded with GTAW method in the cast steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. Furthermore, the corrosion current density of the weld metal zone revealed the lowest value, having the highest value of hardness. The corrosive products with red color and local corrosion like as a pitting corrosion were considerably observed at the base metal zone, while these morphologies were not wholly observed in the weld metal zone. In particular, the polarization characteristics such as impedance, polarization curve and cyclic voltammogran associated with corrosion resistance property were well in good agreement with each other. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the Inconel 625 electrode.

• Journal of Advanced Marine Engineering and Technology
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• 제38권4호
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• pp.409-417
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• 2014

최근 수년 동안 유가의 현저한 상승으로 인하여 상선의 디젤 기관은 저질 중유를 주로 사용하게 되었다. 따라서 저질 중유의 사용 증가에 따른 디젤 기관의 연소실 배기가스 온도는 점차 상승하여 가혹한 부식 환경에 직면하게 되었다. 그 결과 연소실 주변의 모든 기관 부품들의 부식과 마모는 다른 기관 부품들에 비해서 심각하다. 그러므로 이들 부품들의 적절한 덧살 용접은 수명 연장을 위하여 경제적인 측면에서 매우 중요하다. 본 연구에서는 피스톤 크라운 재질로 통상 사용되는 단강에 4종류의 용접재료로 SMAW와 GTAW로 용접하였다. 실험은 모재, 열영향부 및 용접금속의 부식 특성을 35% 황산용액에서 부식전위, 양극분극 곡선, 사이클릭볼타모그램 및 임피던스 등의 전기화학적인 방법으로 하여 고찰하였다. Inconel 625, 718 용접재료의 경우 용접금속의 내식성이 가장 우수하였고, 모재의 내식성이 가장 좋지 않았으며, 반면에 1.25Cr-0.5Mo와 0.5Mo는 모재가 용접금속에 비해서 더 좋은 내식성을 나타내었다. 또한, 용접금속 중 Inconel 625가 가장 내식성이 우수하였으며, 그 다음으로 Inconel 718 용접재료로 나타났다. 경도 역시 용접금속이 상대적으로 모재, 열영향부에 비해서 높은 값을 나타내었다. 특히 Inconel 718 용접재료의 경우 다른 용접재료에 비하여 가장 높은 경도값을 나타내었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.135-148
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• 2017

Topside areas on an offshore oil and gas platform are highly susceptible to explosion. A blast wall on these areas plays an important role in preventing explosion damage and must withstand the expected explosion loads. The uniformly distributed loading condition, predicted by Explosion Risk Analyses (ERAs), has been applied in most of the previous analysis methods. However, analysis methods related to load conditions are inaccurate because the blast overpressure around the wall tends to be of low-level in the open area and high-level in the enclosed area. The main objectives of this paper are to study the effects of applying different load applications and compare the dynamic responses of the blast wall. To do so, various kinds of blast pressures were measured by Computational Fluid Dynamics (CFD) simulations on the target area. Nonlinear finite element analyses of the blast wall under two types of identified dynamic loadings were also conducted.

• 한국기계가공학회지
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• 제18권9호
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• pp.64-71
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• 2019

We herein propose a systematic design method of hydraulic pipes used in heavy construction equipment. We found that even though many design studies have been conducted regarding major hydraulic components such as pumps, cylinders, and control valves, studies regarding the optimal design of hydraulic pipes are scarce. In this study, the design of four types of pipes is considered: two high-pressure and two low-pressure pipes. First, fluid flow analysis was conducted based on oil flow and pressure for various radii of curvature. For a check-valve pipe, we considered the location of an inlet pipe. We could visualize fluid flow inside the pipe according to the flow velocity and pressure distribution. Based on fluid flow analysis, we conducted a structural analysis that revealed the stress distribution and concentration for each pipe design. We selected the best design parameters for each pipe design, fabricated the pipes, and subsequently tested them for validity.