• Journal of Advanced Marine Engineering and Technology
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• 제41권1호
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• pp.21-30
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• 2017

현재 국내에서 공장 보수용접이 가장 많이 이루어지고 있는 선박 엔진 부품은 피스톤 크라운과 배기밸브이다. 또한 선박 엔진 밸브와 크랭크 축 등의 경우에는 신규 부품에서도 성능향상을 위해 표면개질방법으로 오버레이 용접이 시공되고 있다. 용착률을 높이는 고능률 오버레이 용접 공정으로 Hot Wire GTAW, Cold Tandem GMAW, Band Arc SAW, Tandem SAW법이 개발되어 있고, 용사방법으로 PTA공정이 현장에서 많이 시공되고 있다. 입열량 제어가 용이한 공정으로 GMAW-Pulse, CMT 용접공정이 있다. 엔진 배기밸브의 보수를 위한 오버레이공정에서 열영향부에 가까운 모재 내에 액화균열이 발생하는 경우가 있어 주의를 요한다. GMAW-Pulse 공정과 CMT공정에서는 입열량 제어가 용이하여 높은 용착속도를 유지하면서도 액화균열의 발생 없이 엔진 밸브의 보수 또는 표면 개질 목적으로 시공이 가능하다. 최근에 국내에서 고능률 용접 공정으로 선박엔진의 보수 또는 표면 개질 목적으로 사용 가능한 Super-TIG 용접공정이 개발되어 있다. 이 공정은 아크를 플라즈마 스트림이라고 보고 전류증가에 따라 커지는 아크압력을 막으면서도 용가재의 용융 효율이 극대화 되도록 폭이 큰 C형의 오목한 용가재를 발명하여 용착률을 획기적으로 향상시킨 용접공정이다.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.209-217
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• 2013

이 논문은 선박용 디젤엔진의 진동제어에 적용할 수 있는 MR 유체기반 마운트(MR 마운트)의 최적설계를 제시한다. 이 연구에서는 압착모드, 유동모드, 전단모드를 포함하는 혼합모드가 제안되었고 설계되었다. 효과적인 진동제어를 위하여 요구되는 MR 마운트의 작동 댐핑력을 결정하기 위하여 디젤엔진의 기진력이 분석되었다. 이 분석에서 V-type엔진이 고려되었으며 피스톤의 토크에서의 속도와 가스압력간의 관계를 유도하였다. 결과적으로 상업적으로 이용 가능한 MR 유체의 장의존적 유동특성과 기진력을 통합함으로써 적절한 MR 마운트의 크기가 설계되었다. 게다가 기하학적 제한조건이 고려된 최대 구동력을 얻기 위해 ANSYS를 이용하여 최적설계가 수행되었다. 자기밀도분석을 통해 바닥간격과 코일의 반지름과 같은 최적설계변수가 결정되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.93-99
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• 2012

이 논문은 선박디젤엔진의 진동제어에 적용할 수 있는 MR 유체기반 마운트(MR 마운트)의 최적설계를 제시한다. 이 연구에서는 압착모드, 유동모드, 전단모드를 포함하는 혼합모드가 제안되었고 설계되었다. 효과적인 진동제어를 위하여 요구되는 MR 마운트의 작동 댐핑력을 결정하기 위하여 디젤엔진의 기진력이 분석되었다. 이 분석에서 V-type 엔진이 고려되었으며 피스톤의 토크에서의 속도와 가스압력간의 관계를 유도하였다. 결과적으로 상업적으로 이용 가능한 MR 유체의 장의존적 유동특성과 기진력을 통합함으로써 적절한 MR 마운트의 크기가 설계되었다. 게다가 기하학적 제한조건이 고려된 최대 구동력을 얻기 위해 ANSYS 를 이용하여 최적설계가 수행되었다. 자기밀도분석을 통해 바닥간격과 코일의 반지름과 같은 최적설계변수가 결정되었다.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.100-106
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• 1998

The wide open throttle performance and piston temperatures were measured by the change of fuel : gasoline and liquefied petroleum gas(LPG). Bench test method was developed and experimented to study the effect of temperature on the formation of carbon deposit. The bench test results were confirmed by measuring the piston temperature and observing the deposit production rate at an actual engine running condition. Results show that if the fuel of spark ignition engine is changed from gasoline to LPG, the output power decreases about 10% and the piston temperatures increase about 40~55$^{\circ}C$. In actual engine tests, because of this temperature increase, it was observed that the quantity of carbon deposit in the top ring groove increased in a big degree. Consuquently, it is known that the fing sticking may occur if the gasoline engine was rebuilt to LPG fuelled engine. Therefore, in order to preserve the durability of LPG fuelled engine, it is necessary to lower the piston temperature by hardware modificationor to reduce the carbon deposit by the improvement of engine oil.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.143-150
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• 2007

Ring and cylinder bore wear may not be a problem in most current automotive engines. However, a small change in ring face and cylinder bore diameter can significantly affect the lubrication characteristics and ring axial motion. This in turn can cause to change inter-ring pressure, blow-by and oil consumption in an engine. Therefore, by predicting the wear of piston ring face and cylinder bore altogether, the changed ring end gap and the changed volume of gas reservoir can be calculated. Then the excessive oil consumption can be predicted. Here, the oil amount through top ring gap into combustion chamber is estimated as engine oil consumption. Furthermore, the wear theories of ring and cylinder bore are included. The changed oil consumption caused by the new end gap and the new volume of oil reservoir around second land, can be calculated at some engine running interval. Meanwhile, the wear amount and oil consumption occurred during engine durability cycle are compared with the calculated values. The wear data of rings and cylinder bore are obtained from three engines after engine durability test. The calculated wear data of each part are turn out to be around the band of averaged test values or a little below. It is shown that the important factor regarding oil consumption increasement is the wear of ring face.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.107-110
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• 2009

연소불안정현상은 주로 음향파와 열방출률 섭동간의 상호작용에 의해 발생한다고 알려져 있다. 이러한 현상은 헬름홀츠 공진기와 같은 수동제어기를 사용하여 감소시킬 수 있다. 그러나 헬름홀츠 공진기는 일반적으로 좁은 주파수대역에 대해서만 효과가 있는 단점을 가진다. 따라서 본 연구에서는 다양한 작동 범위에서 효과를 가질 수 있도록 피스톤을 사용하여 헬름홀츠 공진기의 부피를 변화시켜가며 연소불안정현상에 적용하였다. 그 결과 피스톤을 최적위치에 동조시킴으로써 연소 불안정 모드의 진폭을 감소시킬 수 있었다. 또한 이러한 결과를 바탕으로 능동적으로 동조되는 수동제어방식의 가능성에 대해서 알아보고자 한다.

• Journal of Advanced Marine Engineering and Technology
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• 제19권2호
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• pp.47-55
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• 1995

When the low heavy oil is using as fuel oil to the diesel engine, some problems such as corrosion resistance, wear resistance and heat resistance are happened in diesel engine's internal material, especially the adhesive wear of piston ring groove was occurred as a important problem. Therefore to prevent adhesive wear of its groove, the surface of its groove used to be electroplated with Chrominum and for its Chromium electroplating, Fe anode is being used until nowadays because of its Special shape. However in case of using Fe anode, there were some problems such as deterioation of solution, property of Chromium film, and condition of coation. In this paper Pb anode electroplated withPb to the steel plate was investigated for its Chromium electroplating for Pb's high corrosion resistance in acid solution, and Pb anode is not dissolved compared with Fe anode and deterioration degree of solution in case of Pb anode is smaller than that of Fe anode and also property of Chromium film was better than that of Fe anode. Moreover it was known that the optimum cathodic current density for Pb electroplating to steel plate as insoluable anode for Chromium coating of piston ring groove is 30mA/$cm^2$ by experimental results obtained.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.238-249
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• 1995

The gas pressure acting on the rings in internal combustion engine influences the friction and wear characteristics. Inter-ring pressure variation during engine operation results from cylinder gas flow through a piston-ring pack. The flow passages consist of ring end gaps and clearances between the ring and the piston groove. The gas flow in the clearance between the ring and the groove is directly affected by the axial motion of the ring in the groove. In this paper the asperity contact force is newly considered in the prediction of the clearence between the ring and the groove surface. This term must be taken into account physically in case that the clearance get narrow rather than asperity height between the ring and the groove surface. Finally, comparisons of calculated inter-ring gas pressures based on the analytical method are made with the measured ones. The agereement was found to be good below midium engine speed, 3000rpm. In order to obtain accurate analytical results to the extend of high rpm range, it is recommended to include oil ring motion as well as top and second ring in analytical model.

• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.98-103
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• 2010

In order to develop two-stroke free-piston hydrogen engine to obtain high thermal efficiency and low emission, backfire occurrence have to be prevented. In this research, backfire characteristics are analyzed as functions of the intake valve opening timing and compression chamber pressure under piston by using RICEM (Rapid Intake Compression Expansion Machine) that has reverse uni-flow scavenging. As the result, reverse uni-flow scavenging is advantage about back fire. but, it exists suitable intake valve opening timing and its timing become known that equivalence ratio 1 retard until the piston rises. Also, To rise chamber pressure of lower piston, this does not cause backfire occurs in equivalent ratio 0.6 observed back fire. Therefore, 2cycle hydrogen fueled free-piston engine is undesirable scavenging compression by compressing the piston.

• 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.