• 한국기계가공학회지
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• 제16권3호
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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.

• 한국추진공학회지
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• 제12권5호
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• pp.1-8
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• 2008

소형 액체로켓엔진 인젝터 분무의 공간분포 특성 규명을 위해 이중모드 위상도플러속도계(DPDA)를 이용한다. 분사압력 및 분무확산방향 이동거리를 변화시켜 분무액적의 크기, 속도 등을 측정하고, 산술평균직경(AMD), Sauter 평균직경(SMD), 수밀도, 스팬(span of drop size distribution), 그리고 체적 유속(volume flux) 등의 분무 매개변수를 도출하여 인젝터 분무의 분열특성을 고찰한다. 분사압력이 증가함에 따라 분무액적의 수밀도, 스팬, 그리고 체적 유속은 증가하지만, AMD는 감소하였다.

• Nuclear Engineering and Technology
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• 제48권2호
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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.

• 소성∙가공
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• 제32권3호
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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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• 제40권6호
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• pp.504-509
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• 2016

이중관 벨로우즈는 우수한 성형성과 내식성을 고려하여 오스테나이트계 스테인리스강인 STS 316L 소재를 사용하여 2겹으로 내부 및 외부 벨로우즈를 각각 제작한 후 다양한 조건과 용접 방법을 적용하여 이중관 벨로우즈를 제작한다. 하지만 제품의 성형 또는 사용시 균열이나 파단에 가장 취약한 부분이 용접부이기 때문에 제품의 신뢰성을 획득하기 위하여 각각의 용접부에 대한 미세조직을 관찰하여 결함 발생 여부를 측정해야 한다. 본 연구에서는 다양한 용접 공정을 거쳐 제작된 벨로우즈의 용접부를 검사하고 미세조직을 분석하여 최적의 용접 조건을 도출하였다. 또한 용접부의 경도 측정을 통해 모재와 용접부 그리고 열영향부 등 용접영역의 기계적 특성을 평가하였다.

• 한국분무공학회지
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• 제26권2호
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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.

• 한국추진공학회지
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• 제21권6호
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• pp.21-31
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• 2017

본 연구에서는 모드 천이가 발생하는 동안 상세한 유동 특성을 조사하기 위해, 이론분석과 수치해석을 수행하였다. 이론분석은 기존의 기체역학과 종래 보고된 이론식들 재정립하였으며, 수치해석은 2차원 비정상 압축성 Navier-Stokes 방정식을 풀기 위해 fully implicit finite volume scheme을 사용해 수행하였다. 해석의 검증을 위하여 실험 결과와 비교하였다. 격리부 입구 전온도와 수소 연료의 당량비를 변화시키면서 모드 천이에 미치는 영향을 조사하였다. 해석과 실험 결과는 정성적으로 잘 일치하였다. 당량비가 증가하면 스크램제트 모드에서 램제트 모드로 천이가 발생하였다. 이 때, 천이는 당량비에 따라 불연속적으로 나타나며, Non-allowable region이 존재하였다. 한편 격리부 입구에서 전온도의 증가는 모드 천이 경계를 변화시켰다.

• 한국추진공학회지
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• 제17권6호
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• pp.81-88
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• 2013

Taylor-Maccoll 유동관계식과 준 1차원 모델을 적용한 구성품 기반의 이중램제트 추진기관 모델 개발에 대해 기술하였다. 이중램제트 흡입구는 Taylor Maccoll 유동관계식을 적용하여 콘 각도 $25^{\circ}$ 형상을 갖는 흡입구에 대해 아음속 및 초음속 흡입구 모델을 구현하였으며 예 연소가스를 초음속 연소기로 전달하는 기능의 가스발생기는 Lumped 모델을 적용하여 모델을 구현하였고 요구되는 노즐목 크기에 대해 기술하였다. 초음속 연소기의 경우 준 1차원 모델을 적용하여 위치에 따른 마하수 변화, 온도변화 및 압력변화 등을 제시하였다. 또한 금번 모델을 이용하여 당량비 및 압력회복율을 고려한 연료량 조절모델에 따른 추력과 비추력을 계산하여 그 결과를 제시하였다.

• 대한조선학회논문집
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• 제49권6호
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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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• 제20권3호
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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.