• Journal of Advanced Marine Engineering and Technology
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• 제39권6호
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• pp.620-625
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• 2015

IMO MEPC에서는 지구온난화를 늦추기 위해서, 선박에서 배출되는 GHG(Green House Gas)인 $CO_2$를 줄이기 위한 방안으로 선속을 다운시켜 운항할 것을 제안한바 있으며, 해운회사에서도 연료비 절감을 위해서 자발적으로 감속운항(Low steaming)을 하고 있어, 국제항해에 종사하고 있는 대부분의 컨테이너선들이 감속운항을 하고 있다. 또한, 날로 증가되고 있는 해운 물동량 증가로 선박의 연료비 부담이 증가되고 있어 연료비 절감 기술개발이 절실히 요구되고 있다. 따라서 본 연구에서는 디젤엔진의 성능을 향상시킬 수 있는 연료첨가제(유용성 칼슘계 유기금속화합물)를 일정량 투입(사용 연료량의 0.025%) 하여 연료비를 절감하는 방법을 시도하였다. 실험의 정확도를 위해서 육상 발전소에 설치된 2행정 대형 디젤엔진을 실험 대상으로 하였다. 실험 엔진의 부하는 저, 중 및 고 부하(50, 75, 100%)로 나누어서 실시하였으며, 연료첨가제의 투입 전과 투입 후의 엔진성능(출력, 연료소비율, 최고연소압력(P-max), 배기온도)을 비교 분석 하였다. 본 실험을 통해서 연료첨가제를 투입함으로써 저부하(50%) 에서 2% 이상의 연료비 절감 효과를 확인 할 수 있었으며, 최고연소압력은 상승하는 반면에 배기온도는 하강함을 알 수 있었다.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.24-30
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• 2004

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthened. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, there is trade off between output and NOx in a HCCI engine. In this study, output and emission characteristics for a gasoline direct injection type HCCI engine were investigated to clarify the effects of intake air temperature, injection time and mixture formation. From these experiments, we found that the smoke was not produced when the fuel was injected earlier than BTDC 90$^{\circ}$. In addition, the output was increased because of delay of ignition time and NOx emission was decreased because of homogeneous charge of first injection in case of split injection.

• Journal of Advanced Marine Engineering and Technology
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• 제32권5호
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• pp.707-716
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• 2008

The objective of this study was to analyze the effect of mixed fuel composition and mass fraction on spray inner structure in evaporating transient spray under the variant ambient conditions. Spray structure and spatial distribution of liquid phase concentration were investigated using a thin laser sheet illumination technique on the three component mixed fuels. A pulsed Nd:YAG laser was used as a light source. The experiments were conducted in a constant volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. Used fuel contains i-octane($C_8H_{18}$), n-dodecane($C_{12}H_{26}$) and n-hexadecane($C_{16}H_{34}$) that were selected as low-, middle- and high-boiling point fuel, respectively. Experimental conditions are 42 MPa, 72 MPa and 112 MPa in injection pressure, $5\;kg/m^3$, $15kg/m^3$ and $30kg/m^3$ in ambient gas density, 300 K, 500 K, 600 K and 700 K in ambient gas temperature, 300 K and 368 K in fuel temperature and different fuel mass fraction. Experimental results indicated that the multi-component fuels made two phase region mixed vapor and liquid so that it would are helpful to improve combustion, for the fuels of high boiling point component could accelerate evaporation very much according as low boiling point fuel was added to high boiling point fuel.

• 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.

• 대한환경공학회지
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• 제27권4호
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• pp.394-401
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• 2005

저온 플라즈마 연료개질 장치를 개발하여 여러 운전인자가 그 성능에 미치는 영향을 조사하였고 생성된 수소농후 개질가스를 무부하(Idle) 상태의 디젤엔진에 연소용 공기와 같이 주입하여 NO와 매연 저감효율에 미치는 영향을 조사하였다 전력 소모량이 증가할수록 개질반응의 점화가 더욱 용이하였으나 $H_2$ 농도, $H_2$ 수율, 에너지 전환율과 같은 저온 플라즈마 연료개질 장치의 성능은 O/C 비에 의해서만 영향을 받았는데 그 이유는 평형 반응온도가 O/C 비에 의하여 결정되기 때문이다. 저온 플라즈마 연료개질 장치에서의 $H_2$ 수율과 에너지 전환율은 O/C 비가 증가함에 따라 O/C 비가 $1.2{\sim}1.5$에서 33.4%와 66%의 최고값을 통과하였다. $H_2$ 수율과 에너지 전환율이 O/C 비가 $1.2{\sim}1.5$ 이하인 범위에서 O/C 비가 증가함에 따라 증가하는 이유는 O/C 비가 높아짐에 따라 완전 산화반응이 충분히 일어나서 반응온도가 높아지기 때문으로 보인다. O/C비가 $1.2{\sim}1.5$ 이상인 범위에서 O/C 비가 증가함에 따라 $H_2$ 수율과 에너지 전환율이 감소하는 현상은 과잉산소 조건에서 완전산화반응이 더욱 촉진되어 $H_2$ 수율과 에너지 전환율이 감소하였기 때문으로 보인다. 무부하 상태의 디젤엔진에 개질가스를 주입시 개질된 디젤/총디젤 무게비가 $18.2{\sim}23.5%$까지 증가할 때 NO저감효율과 매연제거효율은 각각 68.8%와 55.5%까지 증가하였다.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.573-579
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• 2013

Hydrogen engine with homogeneous charged compression ignition can achieve high efficiency by high compression ratio and rapid chemical reaction rates spatially. However, it needs to expansion of the operation range with over-all load conditions which is very narrow due to extremely high pressure rise rate. The adoption of the lean boosting in a HCCI $H_2$ engine is expected to be effective in expansion of operation range since minimum compression ratio for spontaneous ignition is decreased by low temperature combustion and increased surround in-cylinder pressure. In order to grasp its possibility by using lean boosting in the HCCI $H_2$ engine, compression ratio required for spontaneous ignition, expansion degree of the operation range and over-all engine performance are experimentally analyzed with the boosting pressure and supply energy. As the results, it is found that minimum compression ratio for spontaneous ignition is down to the compression ratio(${\varepsilon}$=19) of conventional diesel engine due to decreased self-ignition temperature, and operation range is extended to 170% in term of the equivalence ratio and 12 times in term of the supply energy than that of naturally aspirated type. Though indicated thermal efficiency is decreased by reduced compression ratio, it is over at least 46%.

• 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.

• Asian Journal of Atmospheric Environment
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• 제5권4호
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• pp.237-246
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• 2011

To explore the sources of carbonaceous material in the airborne particulate matter (PM), comprehensive PM sampling was performed (3 to 14 January 2010) at a traffic hot spot site (HS), Farm Gate, Dhaka using several samplers: AirMetrics MiniVol (for $PM_{10}$ and $PM_{2.5}$) and MOUDI (for size fractionated submicron PM). Long-term PM data (April 2000 to March 2006 and April 2000 to March 2010 in two size fractions ($PM_{2.2}$ and $PM_{2.2-10}$) obtained from two air quality-monitoring stations, one at Farm Gate (HS) and another at a semi-residential (SR) area (Atomic Energy Centre, Dhaka Campus, (AECD)), respectively were also analyzed. The long-term PM trend shows that fine particulate matter concentrations have decreased over time as a result of government policy interventions even with increasing vehicles on the road. The ratio of $PM_{2.5}/PM_{10}$ showed that the average $PM_{2.5}$ mass was about 78% of the $PM_{10}$ mass. It was also found that about 63% of $PM_{2.5}$ mass is $PM_1$. The total contribution of BC to $PM_{2.5}$ is about 16% and showed a decreasing trend over the years. It was observed that $PM_1$ fractions contained the major amount of carbonaceous materials, which mainly originated from high temperature combustion process in the $PM_{2.5}$. From the IMPROVE TOR protocol carbon fraction analysis, it was observed that emissions from gasoline vehicles contributed to $PM_1$ given the high abundance of EC1 and OC2 and the contribution of diesel to $PM_1$ is minimal as indicated by the low abundance of OC1 and EC2. Source apportionment results also show that vehicular exhaust is the largest contributors to PM in Dhaka. There is also transported $PM_{2.2}$from regional sources. With the increasing economic activities and recent GDP growth, the number of vehicles and brick kilns has significantly increased in and around Dhaka. Further action will be required to further reduce PM-related air pollution in Dhaka.

• 한국해양공학회지
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• 제30권4호
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• pp.334-340
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• 2016

The combustion chamber of a diesel engine is often exposed to a more serious wear and corrosion environment than other parts of the engine because its temperature increases as a result of using heavy oil of low quality. Therefore, repair and built-up welding methods must be performed on worn or corroded parts of the piston crown, exhaust valve, etc. from an economical point of view. In this study, Inconel 718 filler metal was used in repair welding on the groove of a forged steel specimen for a piston crown, along with built-up welding on the surface of another forged steel specimen. Then, the corrosion characteristics of the weld metal zone for the repair welding and the deposited metal zone for the built-up welding were investigated using electrochemical methods in a 35% H₂SO₄ solution. The deposited metal zone indicated better corrosion resistance than the weld metal zone, showing a nobler corrosion potential, higher impedance, and smaller corrosion current density. It is considered that metal elements with good corrosion resistance were generally included in the filler metal, and these elements were also greatly involved in the deposited meta by built-up welding, whereas the weld metal consisted of metal elements mixed with both the filler metal and base metal elements because of the molten pool produced by the repair welding. Finally, it is considered that the hardness of the weld metal was increased by the repair welding, whereas the built-up welding improved the corrosion resistance of the deposited metal.