• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1077-1079
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• 2017

The cavitation in the turbopump inducer progresses from the inception to the critical point, and finally develops to a breakdown which sharply declined in head. In this paper, we evaluated characteristics and predicted empirical equations about the cavitation inception of a turbopump inducer. The empirical equation of the cavitation inception for the elliptical plate was relatively well predicted to the turbopump inducer. However, in case of the marine propeller, it showed a big difference due to Reynolds number under the operating point.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.518-526
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• 2018

As a new technical approach, this paper introduces a method for improving an electrically propelled outboard motor in consideration of the driving system applied to an electric-propulsion boat with solar cell energy. The most efficient model for a drive shaft, propeller shaft, and bevel gear was suggested and examined with respect to the results of test operation in prototype mode. Furthermore, this research included a performance evaluation of the manufactured prototype to acquire the purposed quantity value and the development items. After manufacturing the desired prototype of an electrically propelled outboard motor, the maximum sail time, thrust force, noise, and weight were evaluated in a performance test. An additional test in relation to the maximum sail speed (knots) of the completed prototype was conducted using a sea trial evaluation to acquire the optimum quantity.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.93-100
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• 2019

The cavitation of a turbopump inducer develops from the inception to a critical point, and encounters breakdown finally. In this study, we evaluated the characteristics and predictions of cavitation inception for the turbopump inducer using empirical equations. The empirical equation for the elliptical plate predicted the generation of cavitation inception of the turbopump inducer relatively well. However, in case of the marine propeller, it showed a considerable difference owing to the Reynolds number of the operating point. The cavitation inception occurred earlier as the number of blades increased. However, the solidity had no major impact on the cavitation inception because the cavitation occurred locally at the tip of the leading edge.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.3
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• pp.146-154
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• 2023

Efforts have been made to reduce the greenhouse gas emissions from ships by limiting the energy efficiency index, and net zero CO₂ emission was proposed recently. The most ideal measure to achieve zero emission ship is electrification, and fuel cells are considered as a practical power source of the electrified propulsion system. The electric efficiency in the electrochemical reaction of fuel cells can be achieved up to 60% practically. The remaining energy is converted to heat energy but most of them are dissipated by cooling. In the author's previous research, a hybrid propulsion system utilizing not only electricity but also heat was introduced by combining electric motor and steam turbine. In this article, long term efficiency is evaluated for the introduced hybrid propulsion system by considering a virtual 24,000 TEU class container carrier model. To reflect a more practical operating condition, the actual navigation data of a similar real ship in the real world were collected from automatic identification system data and applied. From the result, the overall efficiency of the hybrid propulsion system is expected to be higher than a conventional electric propulsion fuel cell ship by 30%.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.841-850
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• 2019

The Korean government has designated speed-limit zones and speed limits in 19 ports and 3 routes to ensure safe navigation and transportation. However, the speed limit differs from port to port, no practical means of management exist. This often leads to violation of the speed limit. Additionally, ship collisions due to human error continue to occur. First, the study analyzed marine accidents that occurred at trade ports and fairways. The result of the analysis revealed the occurrence of 1344 accidents (average 269 cases per year) from 2014 to 2018. Five hundred sixty three accidents involved fishing boats, whereas, merchant vessels were involved in 508 cases. Second, the efficacy of the application of voice and message warnings to GPS plotters and electronic chart display and information system (ECDIS) was reviewed, and these were proposed as measures to inform vessel operators of the hazards of speed limit violation. Third, experts' opinions from relevant agencies and navigation system manufacturers were consulted and it was found that the proposed warning function was technically implementable. The findings are expected to help reduce human error among ship operators and establish a Korean e-navigation system.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.42-52
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• 1997

The basic principle of underwater ram-jet as a unique marine propulsion concept showing vary high cruise speed range(e. g. 80-100 knots) is the thrust production by the transfer of the potential energy of compressed gas to the operating liquid through kinetic mixing process. This paper is aimed to investigate the propulsive efficiency of the nozzle flow in underwater ram-jet at the speed of 80 knots for the buried type vessel. The basic assumption of the theoretical analysis is that mixture of water and air can be treated as incompressible gas. For an optimized nozzle configuration obtained from the performance analysis, preliminary data for performance evaluation are obtained and effects of nozzle inner wall friction, ambient temperature, ambient pressure, water density, gas velocity, bubble radius, flow velocity, diffuser area ratio, mass flow ratio and water velocity gradient are investigated.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.468-472
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• 2015

Recently, there has been increasing interest in the efficient use of energy due to policies related to the reduction of greenhouse gas. This paper suggests a highly efficient sea water cooling system for the load-dependent control of a seawater pump depending on the load, to improve energy efficiency of the warship. This study models the propulsion diesel engine and simulation reflecting the characteristics of the warship operation state that checked the performance of high efficiency sea water cooling system. The simulation results revealed the cooling system of high efficiency with energy savings of approximately 53% compared to the existing cooling systems. These results can be used to improve the performance of the cooling system of the warship propulsion diesel engine in the future.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.1
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• pp.7-13
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• 2021

In recent years, the importance of environmental regulations is increasing in the shipping industry, and the demands of the industry for this are rapidly increasing. Accordingly, the demand of ship owners is increasing as the shaft generator is a technology that responds to environmental regulations that can be applied to ships the fastest. The shaft generator is a device that can increase the fuel consumption rate of the main propulsion engine by installing an electric motor in the main propulsion engine and using it variably according to the load environment. It operates by the power of the motor at low speeds, and when a sudden load is required, the main propulsion engine and motor operate together, enabling efficient operation. In this paper, the diesel engine and shaft generator of a tug boat are modeled using MATLAB Simulink, and the fuel consumption rate is verified through simulation.

• Strategy21
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• s.31
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• pp.251-293
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• 2013

해적은 공해상 해상안전을 위협 한다는 점에서 '인류공동의 적'으로 규정되어 모든 국가가 이를 규제할 수 있는 보편적 관할권이 행사되는 범죄이다. 한국을 포함한 아시아 지역 국가들은 말라카해협 통항에 관해 깊은 이해관계를 갖고 있어 해적 소탕에 대한 의지가 강한 편이다. 이러한 의지는 2006년 '아시아해적퇴치정보공유센터(ReCAAP ISO)'의 창설에 밑거름이 되었으며, 아시아 지역에서 해적이 출현하면 동 센터를 통해 17개국 회원국으로 즉시 통보되고, 주변국의 해경과 해군이 유기적인 작전을 통해 해적을 효율적으로 퇴치하고 있는 모범사례다. 그러나 2009년 소말리아 내란에 따른 무정부 상태가 지속되면서 소말리아 및 아덴만에서의 해적활동이 극성을 부리기 시작했으며, 선박납치 행위가 급증하자 세계 각국에서 함정과 항공기를 파견하여 해적퇴치 활동을 전개하고 있으나 근절되지 않을 뿐만 아니라 해적의 활동해역이 확대되고 있다. 이러한 배경 하에 시작된 본 연구는 연구결과를 중심으로 다음과 같은 대응 방안을 제시한다. 첫째, 소말리아 해적의 근본원인은 국가의 붕괴에서 비롯된 치안부재와 열악한 경제사정 등 내부적인 요인이 크기 때문에 다국적 해군 활동으로 인한 근본적인 해적퇴치에는 한계가 있다. 따라서 국제적인 차원에서 '지역협력협정'체결은 물론, 소말리아 국가재건을 위한 노력이 함께 이루어지는 종합적인 대책이 필요하다. 그러나 보다 더 근본적인 해결책은 유엔차원에서 빠른 시간 내에 소말리아가 정치적 안정을 유지할 수 있도록 정치적 차원에서의 지원이 필요하며, 해적과 테러리스트가 연계됨으로써 국제문제로 확대되지 않도록 하는 노력도 병행되어야 한다. 둘째, 해적문제는 특정국가에만 해당되는 것이 아니라 초국가적인 문제임을 감안하여 유엔안전보장이사회 결의 제1851호에서 '지역 센터' 설립을 권고하고 있는 것처럼 2006년 아시아 국가들이 설치한 ReCAAP ISO와 같은 형태의 지역국가 간 협력기구 또는 유엔 차원의 해적 전담기구를 설치하여 국제사회 공조 하에 해적에 대처하는 방안을 추진하는 것이 필요하다. 셋째, 최근 발생하고 있는 해적행위는 주로 항구 등 내수, 영해 등 연안국의 관할권이 행사되는 지역에서 발생하고 있어 유엔해양법상의 규정은 이러한 '해적' 퇴치에 더 이상 효율적이지 못하다. 국제사회는 이러한 문제점을 인식하여 국제해사기구 (IMO) 등 국제기구를 통해 영해내의 해적 처벌을 위해 최선의 노력을 기울이고 있다. 향후 궁극적으로는 유엔해양법협약의 개정을 통해 법적인 문제점이 개선되어야 한다. 넷째, 전술적인 측면에서도 지상에 기지를 두고 있는 해적들의 지도부가 그 동안 쌓아 놓은 네트워크를 이용하여 다국적 해군에 대한 정보를 수집하고 대응방안을 강구함으로써 나름대로의 생존전략을 구사할 것으로 예상된다. 특히, 선박을 납치한 후 소말리아 연안으로 이동하면서 해군함정과 대치하는 과정에서 해적들이 살상을 당하는 사례가 증가함에 따라 지금까지는 피랍된 선박의 선원을 단순히 해적활동에 참여시키거나, 항해지원을 위한 목적 등으로만 활용했는데, 앞으로는 해적들의 인명피해를 최소화하기 위해서라도 선원들을 방패막이로 활용할 가능성이 더욱 높아질 것으로 예상된다. 따라서 참가하는 해군함정 또는 부대간 해적들의 활동 관련 정보를 공유하는 등 사전에 정보를 획득하기 위한 협력을 강화해야 한다. 다섯째, 한국군함이 삼호주얼리호를 납치했던 소말리아 해적을 한국까지 대리고 와서 처벌하는 것은 불합리하고, 많은 문제점을 야기할 수 있기 때문에 향후 해적처벌을 위한 국제사법기구의 설치가 요구된다. 회원국 분담금으로 운영되는 유엔에 산하기관을 설치하여 소말리아 인접국에서 해결하도록 적극적인 노력을 경주할 필요가 있다. 마지막으로, 선박회사에서도 자국 선박이 위험구역으로 지정된 해역을 항해할 경우를 대비해서 선박자동식별 시스템 구축을 확대하고, 해적이 선박에 승선했을 경우를 대비해서 안전구역(citadel)을 설치하여 선원의 안전을 확보하는 등의 대책이 필요하다. 본 연구를 통해 해양안보는 어느 특정국가에게만 주어진 것이 아니며, 해적행위도 특정 국가의 선박을 대상으로 하는 것이 아니므로 각국 정부간 공동의 협력과 국제사회의 공조가 반드시 실현될 때 해적의 위협으로부터 선박의 안전과 국제사회의 평화가 실현될 수 있다는 것을 강조하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.902-909
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• 2023

This study evaluated the performance test of a small-sized LTE-Maritime(LTE-M) transceiver that was developed and promoted to expand the use of intelligent maritime traf ic information services led by the Ministry of Oceans and Fisheries with the aim of supporting the prevention of maritime accidents. Accoriding to statistics, approximately 30% of all marine accidents in Korean water occur with ships weighing less than 3 tons. Therefore, the blind spots of maritime safety must be supplemented through the development of small-sized transceivers. The small transceiver may be used in fishing boats that are active near coastal waters and in water leisure equipment near the coastline. Therefore, verifying whether sufficient performance and stable communication quality are provided is necessary, considering the environment of their real usage. In this study, we reviewed the communication quality goals of the LTE-M network and the performance requirements of small-sized transceivers suggested by the Ministry of Oceans and Fisheries, and proposed a test plan to appropriately evaluate the performance of small-sized transceivers. The validity of the proposed test method was verified for six real-sea areas with a high frequency of marine accidents. Consequently, the downlink and uplink transmission speeds of the small-sized LTE-M transceiver showed performances of 9 Mbps or more and 3 Mbps or more, respectively. In addition, using the coverage analysis system, coverage of more than 95% and 100% were confirmed in the intensive management zone (0-30 km) and interesting zone (30-50 km), respectively. The performance evaluation method and test results proposed in this paper are expected to be used as reference materials for verifying the performance of transceivers, contributing to the spread of government-promoted e-navigation services and small-sized transceivers.