• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.549-557
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• 2019

The acoustical scattering characteristics of a target are influenced by the material properties and structural characteristics of the target, which are critical information for acoustic detection and identification of underwater target. In particular, for thin elastic target, unique scattered signals are generated around the target by the Lamb wave. In this paper, the results of scattered signal measurement of aluminum spherical shell in the water tank using the stepped frequency sweep sine signal are presented. In particular, the scattering of the water-filled aluminum spherical shell is compared with that of the air-filled one both theoretically and experimentally. The difference of the scattered signals are analyzed using the pseudo Wigner-Ville distribution in terms of average frequency, frequency distribution, and energy of the scattered signal. The result shows that all observed parameters increased when the aluminum sphere was water-filled, and it is well matched to the theoretical expectation.

• Journal of Hydrogen and New Energy
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• v.30 no.3
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• pp.201-208
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• 2019

Recently, a fuel reforming plant for supplying high purity hydrogen is being applied to submarines. Since steam reforming is an endothermic reaction, it is necessary to continuously supply heat to the reactor. A fuel reforming plant for a submarine needs a multi-stage burner (MSB) to acquire heat and convert the combustion gas to $CO_2+H_2O$. The MSB has problems that the combustion imbalance occurs during start-up due to the temperature restriction of the combustion gas. This problems can be solved by burning $H_2O$ together with fuel and $O_2$. In this study, the simulation results of MSB were analyzed to determine the optimum flow rate of $H_2O$ supplied to the 6-stage burner. When the flow rate of $H_2O$ was low, combustion was concentrated on the burner#6 in comparison with the burner#1-#5. This combustion concentration improved as the supply amount of $H_2O$ increased. As a results, it was necessary to supply at least 4.9 kmol/h of $H_2O$ (per 1 kmol/h of fuel) to burner#1 in order to maintain the combustion gas temperature of each stage at $750^{\circ}C$ and to convert the final stage burner gas composition to $CO_2+H_2O$.

• Journal of Hydrogen and New Energy
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• v.30 no.4
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• pp.356-361
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• 2019

Since the government announced the roadmap to revitalize the hydrogen economy, we are constantly making the effort to expand the use of fuel cell electric vehicles (FCEV) and hydrogen charging stations. There is however a significant issue to build and operate the hydrogen charging station due to the lack of the profit model. Many researchers believe that the supply of FCEV will be increased in the near future and finally ensure the economy of hydrogen charging stations. This study shows that the sales changes of hydrogen gas and consumption patterns by the operation of the hydrogen charging station in Changwon City. The results will be used as the evidence to support for operating the hydrogen charging station by private businesses and the validity of additional establishment of hydrogen charging stations.

• Journal of Hydrogen and New Energy
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• v.33 no.6
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• pp.733-742
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• 2022

Hydrogen fuel cell propulsion ships are emerging to respond to the recently strengthened carbon emission regulations in the international shipping sector. Methanol can be stored in a liquid state at normal pressure and temperature, and has the advantage of lower reforming temperature compared to other fuels. In this study, the optimal operating point of the methanol steam reforming system was derived by changing the Steam Carbon Ratio (SCR) from 0.10 to 3.00. Results showed that In terms of methanol conversion rate and hydrogen yield, the larger the SCR is the better, but in terms of system efficiency, it is most advantageous to operate at SCR 0.70 in Pressure Swing Adsorption (PSA) mode and SCR 0.80 in Pd membrane mode. Through this study, it was found that the optimal SCR in the reformer and the entire system including the reformer may be different, which indicates that the optimum operating point may be different depending on the change of the system configuration.

• Plant Journal
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• v.18 no.4
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• pp.66-72
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• 2023

In order to respond to the demand for flexible operation of thermal power generation, development of natural sliding pressure operation that minimizes throttle loss by opening the turbine control valve 100% and maximize power generation efficiency in conjunction with ESS in order to quickly respond to fluctuations in the system frequency is required. The logic development of natural sliding pressure operation with ESS was developed to modify the existing logic at the power plant's top-level control logic such as the unit master, the boiler master and the turbine master. Cooperative control algorithms that complement the advantages and disadvantages of ESS operation (quick response, limited capacity) and power plant operation (slow response, continuous operation) not only improve efficiency when applied to actual power plants, but also respond quickly and flexibly to load demands to ensure system stability.

• Journal of Wind Energy
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• v.14 no.2
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• pp.26-33
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• 2023

In this study, the global response characteristics of floater and mooring for floating offshore wind turbine with a detachable mooring system are performed. Global motion and structural response result extracted from the coupled motion analysis of 10MW DTU floating offshore wind turbine with detachable mooring system modeled by high-order boundary element model and finite element mesh, were used to study the characteristics of tension on mooring lines subjected to three different types of ocean loads. Breaking limit of mooring line characterized by wind, current and wave load has a major effect on the distribution of mooring tension found in time domain analysis. Based on the numerical results of coupled motion analysis, governing equation for calculating the motion response of a floater under ocean loads, and excitation force and surge motion and tension respectively are presented using excursion curve. It is found that the response of floater is reliable and accurate for calculating the tension distributions along the mooring lines under complex loadings. This means that the minimun breaking limit of mooring system satisfied a design criteria at ultimate ocean environmental loading condtions.

• Journal of Wind Energy
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• v.15 no.1
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• pp.91-102
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• 2024

Rapid progress is being made in foundational technology research and engineering for the construction of floating offshore wind farms. There is active development of technology for detachable mooring systems, which have strengths in addressing maintenance issues that arise in floating offshore wind farms and enhance their economic viability. Conventional detachable mooring systems use Kenter links inserted into the middle of mooring chains, which require excessive time for retrieval by Anchor Handling Tug Supply (AHTS) vessels during detachment operations. Moreover, these operations pose risks of link damage and accidents. Therefore, there is a demand for the development of a new concept of detachable mooring systems. The proposed detachable mooring system in this study simultaneously integrates a fairlead chain stoppers (FCS) and submersible mooring pulleys (SMP), which enables all operations to be conducted on the AHTS vessel without underwater tasks. This study detailed the design and safety evaluation of the SMP, a core component of the detachable mooring system, based on the minimum breaking load (MBL) of selected mooring lines according to the capacity of the floating platform. It referenced international codes (AISC Specification for Structural Steel Buildings D5, Pin-Connected Members) for design verification and performed finite element analysis to evaluate the strength of major components in installation and operation scenarios. Additionally, procedures and techniques for evaluating the structural strength of components under uncertain boundary conditions were proposed.

• Journal of Hydrogen and New Energy
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• v.35 no.4
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• pp.353-362
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• 2024

In this study, several studies were conducted on the construction of gas conversion process system for a pilot plant using a small-scale hydrogen liquefaction system. The pilot plant considered in this study includes a liquefier, a storage tank, an evaporator, a gas booster, and a gas storage tank. First, the suspected leak area of the container was checked using the sprayed method of helium gas. The small-scale hydrogen liquefaction system was designed based on the analysis results of the pre-cooling system and the liquefaction system. Additionally, the program was developed to maintain pressure within vessel for an automatic production of liquid hydrogen. The evaporator for liquid hydrogen was manufactured based on the designed analysis data, and the pollution of gas in the vessel was analyzed through a gas recovery line system.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.102.2-102.2
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• 2010

저수지 수면을 이용한 태양광발전 시스템은 저수지, 연못 등의 유휴수면에 부유체를 이용하여 태양광발전 시스템을 수면에 설치하는 발전방식이다. 수면의 환경조건은 지상조건에 비해 장애물이 없고 모듈의 온도가 낮기 때문에 일조량 및 발전효율의 증가 등이 예상되고 있다. 지상 태양광 발전은 농지 또는 임야를 개발하는 과정에서 산림훼손 등을 유발하는 단점이 있으나, 수면태양광 발전은 유효 수면을 적극 활용함으로 국토가 협소한 우리나라에 매우 적합한 발전 방식이라 할 수 있다. 본 논문은 한국수자원공사에서 관리하고 있는 주암 다목적댐에 수면태양광 실증플랜트를 설치한 사례로 설계 및 시공 방법에 대하여 기술하고자 한다.

• JOURNAL OF ELECTRICAL WORLD
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• s.410
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• pp.48-53
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• 2011

발전 및 플랜트 분야의 '청정 산소탱크' 두산중공업. 명장(明匠)은 명품(名品)을 낳고, 이렇게 만들어진 두중의 명품은 지구와 인류의 가치를 드높이고 있다. 발전과 Water사업 분야의 다양한 명품들을 제작해 내고 있는 두중 창원공장. 최첨단 친환경 고효율 발전기술을 보유한 두중은 국내에서 가동 중인 20기의 원전 중 16기에 주기기 공급, HRGS(배열회수보일러) 세계시장 점유율 1위, 자타공인 해수담수화 분야 세계 넘버 원 기업이다. 또한 지난 20년간 세계에서 가장 많은 원전 주기기 공급뿐만 아니라 중국 최초의 3G 원전인 산먼, 하이양 원전 수주, 미국에서 발주된 6기의 AP1000 주기기 전량을 수주하는 기록을 달성하기도 했다. 여기에 더해 최근 두산중공업은 풍력발전 등 신재생에너지 분야와 CCS 등 친환경발전 분야의 기술 상용화부문에서도 가속도를 내고 있다. 일관성과 원칙을 중시하는 박지원 사장의 진두지휘 하에 '경쟁우위의 지속'을 지향하는 두중의 글로벌 가치제고 노력은 여전히 현재 진행형이고, 미래지향적이다.