• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.146-152
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• 2017

Stabilizing the operation of dual fuel diesel engines is very important. The shipbuilding industry is rapidly growing, but gear components requiring reliability are still imported from other countries. The reasoning for this is three-fold. Firstly, it is compulsory that all ships must use devices that meet the performance standards specified in the Safety of Life at Sea (SOLAS) and the convention of MARine POLlution (MAPOL) to prevent pollution caused by ships. Secondly, most ships must comply with the ship classifications specified by ship owners. Therefore, it is specified that key engine gear components must be inspected and authorized for the quality and performance specified by the Ship Register Authority. Thirdly, it is essential that devices (engine gear) for human safety in ships comply with quality standards specified in the regulations and rules by the government. The Ship Register Authority's strict quality standards and approval requirements contribute to the reduction of motivation towards new investment and technology development by device component manufacturers. Therefore, this study aims to develop a method for using infrared thermography to examine gear reliability in order to ensure gear component reliability and national competitiveness in the global market.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.5
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• pp.1-8
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• 2008

Dual-mode Phase Doppler Anemometry (DPDA) was used to scrutinize the spatial distribution characteristics of spray emanating from a small Liquid-Rocket Engine (LRE) injector. Droplet size and velocity were measured according to the variation of injection pressure along the plane normal to the spray stream and then the spray characteristic parameters such as Arithmetic Mean Diameter (AMD), Sauter Mean Diameter (SMD), number density, span of drop size distribution, and volume flux were deduced for an investigation of spray breakup characteristics. As the injection pressure increases, the number density, span, and volume flux of spray droplets become higher, whereas the AMD gets smaller.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.505-517
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• 2016

The structural integrity of a dual-purpose metal cask currently under development by the Korea Radioactive Waste Agency (KORAD) was evaluated, through numerical simulations and a model test, under high-speed missile impact reflecting targeted aircraft crash conditions. The impact conditions were carefully chosen through a survey on accident cases and recommendations from literature. In the impact scenario, a missile flying horizontally hits the top side of the cask, which is freestanding on a concrete pad, with a velocity of 150 m/s. A simplified missile simulating a commercial aircraft engine was designed from an impact loade-time function available in literature. In the analyses, the dynamic behavior of the metal cask and the integrity of the containment boundary were assessed. The simulation results were compared with the test results for a 1:3 scale model. Although the dynamic behavior of the cask in the model test did not match exactly with the prediction from the numerical simulation, other structural responses, such as the acceleration and strain history during the impact, showed very good agreement. Moreover, the containment function of the cask survived the missile impact as expected from the numerical simulation. Thus, the procedure and methodology adopted in the structural numerical analyses were successfully validated.

• Transactions of Materials Processing
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• v.32 no.3
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• pp.107-113
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• 2023

The importance of dual-fuel engines has increased for reducing CO₂ emissions. However, the low operating temperature of this engine may induce low-temperature corrosion at combustion parts, which reduces the engine service life. To overcome this problem, NiCr38Al4 alloy was developed for valve spindle, but the cost of this alloy is expensive due to its high Cr content. For reducing the manufacturing cost of valve spindle, in the present work, NiCr38Al4 alloy was welded with Nimonic80A alloy by conducting friction welding. The tensile test results show that the strength of friction-welded specimens follows the properties of the lower-strength parent materials, without severe cracks at the interface. The large shear strain and frictional heat from friction welding not only reduce grain size but also induce solute element diffusion at the interfacial region. Because of the low Cr diffusivity compared with Ti, Cr carbides were not observed in the Nimonic80A matrix, while Ti carbides were distributed in both the Nimonic80A and SNCrW matrices.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.504-509
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• 2016

Production processes of double wall bellows can be roughly categorized into two steps. In the first step, inner and outer bellows are made of STS316L in austenite stainless steel due to their excellent formability and corrosion resistance. In the second step, the double wall bellows are manufactured using the welding method with both the inner and outer bellows. The microstructure and defects of each weldment are observed to ensure the reliability of bellows since weldment is a highly vulnerable part, which can crack and fracture when bellows are formed or used. In this study, optimum welding conditions were derived from the analysis of microstructure and inspection of weldment of bellows that were produced using various welding procedure. Moreover, the mechanical properties were evaluated through hardness measurement of substrate, weldment and the heat-affected zone.

• Journal of ILASS-Korea
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• v.26 no.2
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• pp.57-66
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• 2021

The reactivity controlled compression ignition (RCCI) is the technology that provides two different types of fuel to the combustion chamber with the advantage of significantly reducing particulate matter and nitrogen oxides emissions. However, due to the characteristics of lean combustion, combustion efficiency is worsened. The conventional type of pistons for conventional diesel combustion (CDC) has mostly been used in the researches on RCCI. Because the pistons for CDC are optimized to enhance flow and target spray, the pistons are unsuitable for RCCI. In this study, a piston that is suitable for RCCI is designed to improve combustion efficiency. The new piston was designed by considering the factors such as squish geometry, bowl depth, and surface area. The experiment was carried out by fixing the energy supply to 0.9kJ/cycle and 1.5kJ/cycle respectively. The two pistons were quantitatively compared in terms of thermal efficiency and combustion efficiency.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.21-31
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• 2017

In the present study, theoretical and numerical analyses have been carried out to investigate the detailed flow characteristics during the mode transition. The theoretical analysis rearranged the knowledge of gasdynamics and the previous studies, and the numerical analysis has conducted to solve the 2D unsteady compressible Navier-Stokes equations with a fully implicit finite volume scheme. To validate the numerical analysis, the experiment was compared with it. The total temperature at the inlet of isolator and the hydrogen fuel equivalent ratio were changed to investigate their effects on the mode transition phenomenon. As the results, the numerical analysis reproduced well the experiment qualitatively, the increment in the hydrogen fuel equivalent ratio induced the scram-mode to ram-mode transition which is discontinuous with a non-allowable region, and the variation in the total temperature changed the boundary of the mode transition.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.81-88
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• 2013

The component based propulsion modeling and simulation of an dual ramjet engine using Taylor-Maccoll flow equation and quasi 1-D combustor model. The subsonic and supersonic intake were modeled with Taylor-Maccoll flow having $25^{\circ}$ cone angle, the gas generator which transfers a pre-combustion gas into supersonic combustor was developed using Lumped model, and the determination of the size of nozzle throat of a gas generator was described. A quasi 1-D model was applied to model a supersonic combustor and the variation of temperature and pressure inside combustor were presented. Furthermore, the thrust and specific impulse applying fuel regulation by pressure recovery ratio and equivalence ratio were derived.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.6
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• pp.447-460
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• 2012

In this study, the shutdown system of the fuel gas supply system is designed based on the Safety Integrity Level of IEC 61508 and IEC 61511. First of all, the individual risk($10^{-4}$/year) and the risk matrix which are the risk acceptance criteria are set up for the qualitative risk assessment such as the HAZOP study. The natural gas leakage at the gas supply pipe is identified as the highest risk among the hazards identified through the HAZOP study and as a safety instrumented function the shutdown function for leakage was defined. SIL 2 and PFD($2.5{\cdot}10^{-3}$) for the shutdown function are determined by the layer of protection analysis(LOPA). The shutdown system(SIS) carrying out the shutdown function(SIF) is verified and designed according to qualitative and quantitative requirements of IEC 61508 and IEC 61511. As a result of SIL verification and SIS conceptual design, the shutdown system is composed of two gas detectors voted 1oo2, one programmable logic solver, and two shutdown valve voted 1oo2.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.3
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• pp.19-28
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• 1996

In Asia countries the productions of ship building and marine engines have been increasing, specially Japanese marine industries have worked hard after 1960s and Korean ones after 1980s. Recently the other countries, as Taiwan and China, have been working so that these hour Asian countries are occuping the high level of shared ratio of productions for gross tonnages and horse powers, which are 74 and 64[%] of the world ones ($8.6\times10$+6[GT], $8.6\times10$+6[PS]) in 1994. Korean industries had the highest shared ratio of production of tanker vessel and 2 stroke diesel engine as 45[%]($2.2\times10$+6[GT]) and 37[%]($1.0\times10$+6[PS]) which were more than those of Japan as 34 and 16[%] in 1989 respectively. Some marine databases and their network links among Asian countries are proposed due to the posibility of collection and analyses with their own specifications by the marine industries and operators as well as Japanese ship reliability investigation works(SRIW) like SRIC in Japan. During 1966 and 1996 16 times of SRIW in Japan have been carried out by ship reliability investigation group(SRIG) in Japan. There have been collected and evaluated a great number of field data of failures and maintenances($700\times10$+3[occ], $1.6\times10$+6[MH}) during running hours($13.4\times10$+6[Hrs]), from which many kinds of evaluation indices could be gotten as the three indices of occurring rate$\lambda$(52.2[occ/1000Hrs]), average man-hour mh(2.29[MH/occ]) and manning index MI(119[MH/1000Hrs]). An estimation example having the three indices$\lambda$, mh and MI were shown by the SRIC 1990 Data Base in Japan for the two kinds of fuel oil suppling subsystems which are dual fuel oil one(DFOS) and mono fuel oil one(MFOS). Three indices MI, and mh for DFOS and MFOS results in 7.16 and 5.20[MH/1000Hrs], 2.63 and 2.06[occ/1000 Hrs]. Therefore the more simple subsystem MFOS can save approximately 30[%] of maintenance load. Finlly an utilization methods are shown for the SRIC in Japan by means of computer system and worlwide internet links.