• International journal of advanced smart convergence
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• 제10권2호
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• pp.15-20
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• 2021

We constructed an air-lifted seawater propulsion system for decreasing fuel consumption of the ships. The system has a form of pipes which can be easily installed on the sides of the ship. Seawater mixed with air, will rise along within the pipe, and will be discharged downward. If the directions of inlet / outlet of the pipe are designed properly, a propulsive energy can be obtained. We tested the system with a model ship in Jangsa port at Sokcho-city with a water depth of 2.5 meters. The system was supplied regulated air at 6 bars during the 3 tests. The model ship was moving forward at a rate of 0.18 meters per second. In case of large ships equipped zfrom clean energy.

• 대한조선학회논문집
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• 제59권1호
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• pp.46-54
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• 2022

A magnetohydrodynamic (MHD) seawater propulsion thruster has been proposed to reduce propeller noise, propeller pitting, and vessel vibration originated from the propeller cavitation. The MHD thruster was also focused to overcome the limitation of propulsion velocity for the special purpose of marine ships. The research trends and key technologies in the worldwide leading countries are reviewed for the development of MHD propulsion thrusters in Korea. A small performance test device was developed firstly with a conventional solenoid magnet of ≤0.6 Tesla and a helical-type cylindrical duct(inner diameter of 5 cm) of thruster. The artificial seawater was fabricated by a salt solution including a conductivity of 5~6 S/m. The measured flow velocity of artificial seawater in the test device was 0.03~0.42 m/s (0.06~0.84 Knot) with a magnetic field strength of 0.6 Tesla and the applied currents of 10~80 A including the change of anode materials. It was found that the flow direction of seawater was reversed by the directional change of applied current in the solenoid magnet.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.128-130
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• 2017

수중추진을 위한 고체추진제로 알루미늄 분말의 수반응성을 높이기 위하여 $NaBH_4$를 첨가하였다. 알루미늄 분말은 $NaBH_4$의 첨가량에 따라 다른 연소특성을 보였다. $NaBH_4$를 첨가하였을 때 끓는점보다 훨씬 낮은 온도에서도 물과 반응하여 연소되었다. 본 연구에서 $NaBH_4$는 Al 분말과 증기 반응을 촉진시키는 효과적인 첨가제임을 확인하였다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4335-4349
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• 2023

Nuclear marine propulsion has been emerging as a next generation carbon-free power source, for which proper passive residual heat removal systems (PRHRSs) are needed for long-term safety. In particular, the characteristics of unlimited operation time and compact design are crucial in maritime applications due to the difficulties of safety aids and limited space. Accordingly, a compact and long-term-operable PRHRS has been proposed with the key design concept of using both air cooling and seawater cooling in tandem. To confirm its feasibility, this study conducted system design and a transient analysis in an accident scenario. Design results indicate that seawater cooling can considerably reduce the overall system size, and thus the compact and long-term-operable PRHRS can be realized. Regarding the transient analysis, the Multi-dimensional Analysis of Reactor Safety (MARS-KS) code was used to analyze the system behavior under a station blackout condition. Results show that the proposed design can satisfy the design requirements with a sufficient margin: the coolant temperature reached the safe shutdown condition within 36 h, and the maximum cooling rate did not exceed 40 ℃/h. Lastly, it was assessed that both air cooling and seawater cooling are necessary for achieving long-term operation and compact design.

• 한국추진공학회지
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• 제16권6호
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• pp.9-15
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• 2012

추력변화를 초공동 수중운동체의 추진체로 사용되는 수반응성 금속입자와 해수는 연소챔버 내에서 균질하게 혼합될 때 비추력이 극대화 된다. 본 연구의 목적은 상사성의 관점에서 분사기 형상이 입자 분포에 미치는 영향을 알아보는 것이다. 이를 위해 PIV기법을 이용하여 반경방향의 입자 분포와 입자 평균속도의 상사성에 대하여 알아보았다.

• 에너지공학
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• 제2권1호
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• pp.38-44
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• 1993

Electromagnetic seawater thrusters may be classified into four general categories : internal duct dc, external field dc, internal peristaltic ac, and external peristaltic ac. Internal duct dc thrusters offer the advantages of low magnetic field leakage, simple construction, and potentially high reliability. The most efficient internal duct configuration consists of converging inlet nozzle and a straight discharge duct. Ideal efficiency calculations based on the one-dimensional Bernoulli equation show that thrusters should be designed with large cross-sectional areas and operate at low discharge velocities. In practice, this may be accomplished by using multiple thruster ducts. Conductivity enhancement, high magnetic fields, and long electrodes will also improve efficiency.

• 에너지공학
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• 제8권4호
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• pp.546-552
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• 1999

In order to obtain the highly effective thermal energy from jacket cooling water of propulsion diesel engines. a development of the Fresh Water Generator (FWG) with a capacity of 30 ton/day was implemented. Newly developed experimental devices and data acquisition system were used to evaluate the performance of the FWG. In this study experiments were performed for various driving pressures by varying the mass flowrate of cooling seawater with or without a heat source instead of jacket cooling water.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• 한국수소및신에너지학회논문집
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• 제25권3호
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• pp.271-279
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• 2014

A 25kW-class polymer electrolyte membrane (PEM) fuel cell system has been developed for the propulsion of a leisure boat. The fuel cell system was designed to satisfy various performance requirements, such as resistance to shock, stability under rolling and pitching oscillations, and durability under salinity condition, for its marine applications. Then, the major components including a 30kW-class PEM fuel cell stack, a DC-DC converter, a seawater cooling system, secondary battery packs, and balance of plants were developed for the fuel cell system. The PEM fuel cell stack employs a unique design structure called an anodic cascade-type stack design in which the anodic cells are divided into several blocks to maximize the fuel utilization without hydrogen recirculation devices. The performance evaluation results showed that the stack generated a maximum power of 31.0kW while maintaining a higher fuel utilization of 99.5% and an electrical efficiency of 56.1%. Combining the 30-kW stack with other components, the 25kW-class fuel cell system boat was fabricated for a leisure. As a result of testing, the fuel cell system reached an electrical efficiency of 48.0% at the maximum power of 25.6kW with stable operability. In the near future, two PEM fuel cell systems will be installed in a 20-m long leisure boat to supply electrical power up to 50kW for propelling the boat and for powering the auxiliary equipments.

• Journal of Advanced Marine Engineering and Technology
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• 제39권4호
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• pp.468-472
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• 2015

최근 대두되는 선박배기가스 저감 등의 환경정책으로 인하여 에너지의 효율적 이용에 관심이 증가하고 있다. 본 논문에서는 함정의 에너지 효율 향상을 위하여 사용 부하에 따라 해수펌프를 제어하는 고효율 해수냉각시스템을 제안한다. 본 논문에서는 제안하는 시스템의 효과를 알아보기 위하여 추진 디젤기관의 냉각시스템을 모델링 하고 함정 운항특성을 고려한 시뮬레이션을 수행하였다. 시뮬레이션 결과 제안한 고효율 해수냉각시스템이 기존 해수냉각시스템에 비하여 약 53%의 에너지 절감효과가 있었다. 본 연구 결과는 향후 함정 추진 디젤기관의 해수냉각시스템의 성능 향상에 유용한 자료로 활용될 수 있다.