• 대한조선학회논문집
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• 제57권3호
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• pp.160-167
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• 2020

A two-stroke diesel engine and a propeller normally adopted in large merchant ships are regarded as major ship vibration sources. They are directly connected and generate various excitation components proportional to the rotating speed of diesel engine. Among the components, the magnitude of two excitation components with the same frequency generated by both engine and propeller can be compensated by the adjustment of their phase difference. It can be done by the optimization of propeller assembly angle but requires a number of burdensome trials to find the optimal angle. In this paper, the efficient estimation method to determine optimal propeller assembly angle is proposed. Its application requires the axial vibration measurement in sea trial and the numerical vibration analysis for propulsion shafting which can be substituted by additional vibration measurement after one-trial modification of propeller assembly angle. In order to verify the validity of the proposed method, the phase difference between two fifth order excitation components generated by both diesel engine and propeller of a real ship is calculated by the finite element analysis and its result is indirectly validated by the comparison of axial vibration responses at intermediate shaft obtained by the numerical analysis and the measurement in sea trial. Finally, it is numerically confirmed that axial vibration response at intermediate shaft at a resonant speed can be decreased more than 87 % if the optimal propeller assembly angle determined by the proposed method is applied.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.578-583
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• 1997

Abstract-Crosshead bearing in two-stroke marine diesel engine is operated under quite severe condition since the load on the bearing is sybject to the loading in a unidirectional and the sliding speed is very slow and oscillatory. So it is very difficult to form oil film and maintain the load. In this paper, two types of bearing are compared. One has large sized oil pocket and the seleted as multi-small oil grooves. Bearing clearance, oil inlet oressure and bearing types are selected as analysis parameters. Loci of journal center are presented to compare several cases. It is found that bearing clearance and shape affect to minimum film thickness.

• 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.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.981-988
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• 2008

This paper describes a development of automatic measuring device for cylinder liner wear amount. An operator should regularly measure the wear amount of the cylinder liner to prevent the wear amount of the cylinder liner from exceeding the maximum limit specific to the engine type. In previous methods. an operator entered the inside of the cylinder liner on a ladder and measured the amount of wear using a inside micrometer. Such method is unpleasant in severe environments and full of hazards. In addition, in order to enter the cylinder, the piston head had to be detached. requiring much time and money. In order to solve these problems, a new measuring device that consists of two measuring units and a special install jig is developed. The measuring units are installed through the scavenging air port by the install jig and measures the wear amount during 1 revolution of crankshaft. so detaching of the cylinder head and entering inside the cylinder liner are not required.