• Journal of the Society of Naval Architects of Korea
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• v.32 no.2
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• pp.103-107
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• 1995

Longitudinal hull girder vibration has not been occurred severely since 1960's. However, recent low speed diesel driven ships equipped with overcritical shafting system, can be excited heavily in longitudinal direction by shaft axial farce coupled with torsional vibration. In this study the characteristics of longitudinal hull girder vibration of a 73,000 deadweight bulk carrier were investigated through onboard measurement, exciter test, and 3-D FEM analysis. Results showed that the longitudinal hullgirder vibration may occur in the ship which is not set up the barred speed range in engine operation. Moreover, this vibration occurs. only during the low speed voyage in harbour depending upon the ship loading condition.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.497-504
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• 2023

In this study, Selective catalytic reduction (SCR) + Diesel particulate filter (DPF) system was installed on a ship with a low-speed engine to conduct the on-board test. The target ship (2,881 gross tons, rated power 1,470 kW@240 rpm ×1) is a general cargo ship sailing in the coastal area. Drawing development, approvals and temporary survey of the ship were performed for the installation of the after-treatment system. For performance evaluation, the gaseous emission analyzer was used according to the NOx technical code and ISO-8178 method of measurement. The particulate matter analyzer used a smoke meter to measure black carbon, as discussed by the International Maritime Organization (IMO). Tests were conducted using MGO (0.043%) and LSFO (0.42%) fuels according to the sulfur content. The test conditions were selected by considering the engine rpm (130, 160 and 180). Gaseous emission and particulate matter (smoke) were measured according to the test conditions to confirm the reduction efficiency of the after treatment system. The results of NOx emission and particulate matter (smoke) revealed that reduction efficiency was more than 90%. The exhaust pressure met the allowable back pressure (less than 50 mbar). This study confirms the importance of the on-board test and the potential of SCR + DPF systems as a response technology for reducing nitrogen oxides and particulate matter.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.345-346
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• 2010

본 연구에서는 모형실험 및 수치계산에 의해 정수중 부선 주위의 유통해석을 실시하였으며, 이를 통하여 객관적이고 정량적으로 부선의 저항추진 성능을 파악할 수 있었다. 먼저 희류수조에서 모형실험을 실시한 후, 실험에서 얻어진 데이터와의 비교를 통한 CFD의 유효성을 검증하고, 다른 형태의 예부선 선박 주위의 유동장 계산에 적용시켜 해결할 수 있는 가능성을 확인 하였다. 부선의 선수 형상에 의하여 저속일 때 25% 정도의 저항이 차이나는 현상을 모형실험을 통하여 파악할 수 있었으며, 유효마력은 7kts부터 급격히 증가하므로 적재상태별 경제적인 운항속력을 선정하여 효율적인 예부선 업무를 수행해야 할 것으로 판단된다.

• Journal of Navigation and Port Research
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• v.47 no.6
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• pp.305-314
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• 2023

In this study, a mathematical model of a 9.77 G/T small fishing vessel was established based on captive model tests. The powering and manoeuvring performances of the vessel in the harbor and coastal sea were focused on, so captive model tests were conducted up to the full-scale speed of 8 knots. Propeller open water, resistance, and self-propulsion tests of a 1/3.5-scaled model ship were performed in a towing tank, and the full-scale powering performance was predicted. Hydrodynamic coefficients in the mathematical model were obtained by rudder open water, horizontal planar motion mechanism tests of the same model ship. In particular, in static drift and pure yaw tests which were conducted at a speed of 2 to 8 knots, the linear hydrodynamic coefficients varied with the ship speed. The effect of the ship speed on the linear coefficients was considered in the mathematical model, and manoeuvring motions, such as turning circles and zig-zags, were simulated with various approach speeds and analyzed.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.399-404
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• 2015

The cost of fuel in ships has recently increased due to a rapid increase in international oil prices and international restrictions regarding the greenhouse effect generated from the burning of fuel. Therefore, different methods for changing the hull designs for improving energy efficiency, developing coating for reducing friction resistances, developing additives for improving engine thermal efficiency, and low-speed operation for reducing fuel consumption have been considered. The developments of high-speed, large-scale, and energy-saving vessels are deemed essential to adapt to the recent high oil price era. Therefore, it is important to analyze Precisely the qualitative and quantitative changes in the resistance value of the local areas of the hull surface. In this study, the engine performance before and after docking was analyzed to examine friction resistance caused by marine growth on the hull as a basic study for improving the energy efficiency. The result was then presented by comparing it with the previous data for 2.5 years between docks to investigate the performance of the main engine, the change in friction resistances and loads, the fuel consumption and ship speed.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.2
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• pp.95-109
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• 2023

In the 4th industrial revolution, changes in the technological paradigm have had a direct impact on the maintenance system of ships. The 2-stroke low speed engine system integrates with the core equipment required for propulsive power. The Condition Based Management (CBM) is defined as a technology that predictive maintenance methods in existing calender-based or running time based maintenance systems by monitoring the condition of machinery and diagnosis/prognosis failures. In this study, we have established a framework for CBM technology development on our own, and are engaged in engineering-based failure analysis, data development and management, data feature analysis and pre-processing, and verified the reliability of failure mode DB using LSTM algorithms. We developed various simulated failure mode scenarios for 2-stroke low speed engine and researched to produce data on onshore basis test_beds. The analysis and pre-processing of normal and abnormal status data acquired through failure mode simulation experiment used various Exploratory Data Analysis (EDA) techniques to feature extract not only data on the performance and efficiency of 2-stroke low speed engine but also key feature data using multivariate statistical analysis. In addition, by developing an LSTM classification algorithm, we tried to verify the reliability of various failure mode data with time-series characteristics.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.3
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• pp.269-274
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• 2009

Recently, the construction of Liquefied Natural Gas Carriers(LNGC) is being promoted larger and larger depending on long voyage. In 1950 years, $5,000m^3$ class of LNGC had been changed to $71,500m^3$ class in 1973. and to $210,000-266,000m^3$ class in 2007. Especially, the system of main engines and cargo control, Re-liquefaction of natural gases have become possible in LNGC. This research deals with the LNG projects, world markets of energy and developing tendency of liquefied natural gas carriers.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.207-212
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• 2006

The noise levels on board ship recognized at Europe in the early 1970s and the noise regulations on board ship began to put in a statutory form. After that, in 1982 "International Code on Noise Levels on Board Ships" adopted by IMO and it became standard to the newly built ship and remain so to this day. Especially, the ship engine room, which have huge main engine and various kinds of subsidiary machines, is under an extremely loud condition and so the worker who works in it is easy to lose his hearing. Recently, each nation regulates the allowable noise exposure time by law to protect the industrial employee from the occupational hardness of hearing. In our country, the allowable noise exposure time is regulated by the labor standard law but the international provisions regulated by IMO have been applied in case of the ship engine room. In this paper, the cabin's noise levels of cargo-passenger ships plies south-west coast line were investigated.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.1
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• pp.83-88
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• 2011

There are various environmental conditions under which ship may navigate over ocean or in harbor. Ship's torque and speed change frequently under the voyage conditions. In this case, harmonics is created in the electrical power systems. The major adverse impacts of voltage and current harmonics in the electrical power systems on generator, transformer, converter, inverter and propulsion motor lead to the increase of machine heating caused by iron and copper losses which are dependent on frequency. In this paper, an analysis of THD(total harmonic distortion) for currents and voltages in the propulsion equipment was carried out. The THD and torque ripple in the input currents of the propulsion motor have been confirmed by the simulation results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.10
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• pp.857-864
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• 2016

Many plane, UAV and drone fly in the sky as development of aviation industry. Plane and UAV fly and drone's propellers rotate so fast. Impact between flying objects which have high velocity threats passengers. Also the impact damages people, building and various property. Plane's operating speed is near sound velocity(340m/s), and propeller's rotating speed is less than that. Until now, impact experiment uses gas gun to get speed and the gun needs large space to entirely air expansion. Electromagnetic launcher, especially railgun, needs smaller space than gas gun to get enough speed about 500m/s. This paper explains electromagnetic launcher's operating principle, shows making electromagnetic launcher design guide line and suggests that it is a better apparatus to get low-high velocity.