• 한국소음진동공학회논문집
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• 제24권6호
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• pp.452-461
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• 2014

Two stroke low speed diesel engines that have many advantages such as high thermal efficiency and durability have been widely used for marine engine. However, it is also true that many problems have occurred due to the high explosion pressure and severe operating environment. Especially problems of shaft damage etc. intensively occurred due to the phenomenon of crankshaft exceeding the allowable stress, including the shaft vibration of the engine model in the early stage. In this study, the crankshaft fracture phenomenon of early engine model was evaluated and analyzed by using up-to-date torsional vibration calculation program and measurement instrument. And this was numerically shown.

• 한국소음진동공학회논문집
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• 제23권9호
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• pp.806-813
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• 2013

For the past years, higher power rating 2 stroke super long stroke diesel engines having more than 8 cylinders and larger cylinder bore are installed mainly on very large containerships to save on fuel consumption. However, these engines are prone to X-mode vibration due to 2nd node torsional vibration or the X-type moment, particularly because of the increase in total length and height. Recently, cases of excessive X-mode vibration often occurred on engine's major components. This vibration is manifested also as secondary vibration causing failure in engine-mount large structures. This study investigated the excitations caused by the 2nd node propulsion shafting torsional vibration that influence X-mode vibration of the main engine and practical countermeasures are proposed. An 8RT-flex82T 8 cylinder engine and 11S90ME-C 11 cylinder engine for a container ship was used as research model.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1472-1479
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• 2002

Environmental protection on the ocean has been interested and nowadays the International Maritime Organization(IMO) has advanced on the prevention of air pollution from ships. This study presents the emission characteristics of 4 stroke marine diesel engines in E3 cycle (propulsion application) and D2 cycle (generation application). Also the effects of important operating parameters in terms of intake air pressure and temperature, and maximum combustion pressure on the specific emissions are described. Emissions measurement and calculation are processed according to IMO Technical Code. The results show that NOx emission level in E3 cycle is higher than that in D2 cycle due to lower engine speed at low load and the maximum combustion pressure by fuel injection timing control and intake air temperature has strong influence on NOx emission production. And CO, HC emissions are not affected by maximum combustion pressure and intake air pressure and temperature.

• Journal of Advanced Marine Engineering and Technology
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• 제29권2호
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• pp.161-167
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• 2005

The improvements of the propulsive engine efficiencies could reduce the fuel consumption. Therefore. for a marine main diesel engine the substantial increase of stroke bore ratio. so that the engine speed can be significantly reduced in order to increase the Propulsive efficiency. As a typical example. a Sulzer RTA 60C engine has acylinder diameter of 600 mm and each cylinder is capable of delivering 2.369 kW in the speed range 91-114 rpm. In order to Provide basic data for thermal system of marine engine. this work performs an experimental study of heat transfer in a square channel with one rib-roughened wall under sin91e mode of reciprocating oscillation. A selection of heat transfer measurements illustrates the manner by which the reciprocating channel with two opposite heating walls has the higher heat transfer Performance than with four heating wall.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.549-554
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• 2013

For the past years, higher power rating 2 stroke super long stroke diesel engines having more than 8 cylinders and larger cylinder bore are installed mainly on very large containerships to save on fuel consumption. However, these engines are prone to X-mode vibration due to $2^{nd}$ node torsional vibration or the X-type moment, particularly because of the increase in total length and height. Recently, cases of excessive X-mode vibration often occurred on engine's major components. This vibration is manifested also as secondary vibration causing failure in engine-mount large structures. This study investigated the excitations caused by the $2^{nd}$ node propulsion shafting torsional vibration that influence X-mode vibration of the main engine and practical countermeasures are proposed. An 8RT-82RT-flex 8 cylinder engine and 11S90S-ME 11 cylinder engine for a container ship was used as research model.

• 동력기계공학회지
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• 제19권3호
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• pp.16-21
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• 2015

Nitrous oxide($N_2O$) concentration in the atmosphere has been constantly increased by the human activities with industrial growth after the industrial revolution. One of factors to increase $N_2O$ concentration in the atmosphere is the $N_2O$ emission caused by the combustion of marine fuel. Especially, a sulfur component included in marine fuel oils is known as increasing the $N_2O$ formation in diesel combustion. Form this point of view, $N_2O$ emission from a ship is not negligible. On the other hand, Exhaust gas recirculation(EGR) that have thermal, chemical and dilution effect is effective method for reducing the NOx emission. In this study, an author investigated $N_2O$ reduction by using EGR on a direct injection diesel engine. The test engine was a 4-stroke diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of the engine was a fixed load of 75%. The experimental oil was a blend-fuel that were adjusted with sulfur ratio of 3.5%, and EGR ratio of 0%, 10%, 20% and 30%. In conclusion, diesel fuel that contained 3.5% sulfur component increased $SO_2$ emission in exhaust gas, and increment of EGR ratio reduced NO emission. Moreover, $N_2O$ emission was decreased as over 50% at EGR ratio of 10% and reduced 100% at EGR ratio of 30% compared with $N_2O$ emission of 0% EGR ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1051-1056
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• 2014

아산화질소($N_2O$, Nitrous Oxide)는 박테리아의 물질대사와 같은 생물학적인 활동에 의하여 자연적으로 발생한다. 하지만, 최근의 대기 중 $N_2O$는 산업의 성장과 같은 인간의 활동에 의하여 증가되어져 왔다. 이 중에 대기 중의 $N_2O$농도를 증가시키는 요인들 중에 하나는 선박용 연료 연소로부터 발생하는 $N_2O$이다. 현재 해상 운송은 국제 물류의 99퍼센트 이상을 담당하고 있고, 선박척수는 물동량의 증가와 함께 증가하고 있다. 따라서, 본 연구에서는 4-행정 선박용 디젤엔진을 사용하여 다른 성분 농도들을 포함하는 연료의 연소가 $N_2O$ 배출률에 미치는 영향에 대하여 실험적인 조사를 실시하였다. 또한, 연소실 내의 연료 연소 패턴이 $N_2O$ 배출률에 미치는 영향에 대하여 평가하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제10권2호
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• pp.146-155
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• 1986

Until recently, the calculation of torsional vibration for the marine diesel engine shafting has been performed only for vibratory stresses of resonant points and vibratory stresses for other engine speeds are determined by the estimation. With the advent of energy-saving engines which have a long stroke and a small number of cylinders, the first major critical torsional vibration of the propulsion shaft appears ordinarily near the MCR speed of engine and the flank of its vibratory stress exceeds now and then the limit stress defined by the rules of Classification Society. In order to know the above condition in the design stage of propulsion shafting, it is necessary to calculate the forced torsional vibration with the damping of propulsion shafting for all orders and to synthesize its calculated results according to their phase angles. In this study, the forced torsional vibrations with the damping of propulsion shafting are calculated for several orders by mechanical impedance method, and their results are synthesized. A computer program for above calculations are developed and some test-runs of the developed program are performed for propulsion shaftings of actual ships. The results of calculations are compared with measured values and also with those of the modal analysis method. They show fairly good agreements and the developed program is checked up on its reliability.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.572-578
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• 2007

Two stroke low speed diesel engines are widely used for marine propulsion or as power plant prime mover. These engines have many merits which includes higher thermal efficiency, mobility and durability. Yet various annoying vibrations occur sometimes in ships or at the plant itself. Of these vibrations, torsional vibration is very important and dictates a careful investigation during the engme's initial design stage for safe operation. With the rule and limit on torsional vibration in place, shaft strength fatigue due to torsional vibration however demands further analysis which possibly can be incorporated in the classification societies' rule and limit. In addition, the shaft's torsional vibration stresses can be calculated equivalently from accumulated fatigue cycles number due to transient torsional vibration in time domain. In this paper, authors suggest a new estimation method combined with Palmgren-Miner equation. A 6S70MC-C ($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study. Angular velocity was measured, instead of shaft's strain, for simplified measurement and it was converted to torsional vibration stress for accumulated fatigue cycle numbers in shafting life time. Likewise, the accumulated fatigue calculation was compared with shaft fatigue strength limit. This new method can be further realized and confirmed in ship with two stroke low speed diesel engine.

• Tribology and Lubricants
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• 제13권2호
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• pp.46-51
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• 1997

Crosshead bearings in two-stroke marine diesel engines are operated under severe conditions of lubrication because the load on the bearing is unidirectional and the sliding speed is very low and oscillatory. In this paper, the motion of journal in a bearing is investigated using the lubrication theory. Several locus paths are presented to show the effects of oil groove size, bearing clearance and oil inlet pressure. It is found that the minimum film thickness is affected by the oil groove and bearing clearance, and the oil groove is an important design factor.