• 수산해양기술연구
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• 제23권2호
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• pp.40-40
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• 1987

열선유속계를 이용하여 디이젤 기관 연소실내의 한점에서 유속을 측정한 결과는 다음과 같은 결론을 얻었다. 1. 연소실내의 유동은 cylinder의 원주방향의 속도 성분이 크며, 유속변화는 밸브 timing과 피스톤 속도등에 밀접한 관계가 있다. 2. 유속은 흡입시부터 증가하여 압축행정중 흡입밸브가 닫히는 60°ABDC에서 최대치를 갖고 이후 피스톤의 속도가 감소함에 따라 유속도 감소하여 팽창행정중 배기 밸브가 열리는 120°ATDC에서 다시 증가하였다. 3. 평균유속은 shroud 밸브 사용시가 no shroud 밸브 사용시보다 낮지만 shroud 밸브 사용시 흡입행정에서 난류강도가 가장 크게 나타났다. 4. 90°shroud 밸브 사용시가 120°shroud 밸브 사용시보다 난류강도는 더 크고, 90°shroud의 180°위치에서 난류강도가 제일 크게 나타났다.(이 논문의 결론부분임)

• 대한기계학회논문집B
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• 제40권9호
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• pp.569-576
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• 2016

본 연구는 HSDI 디젤 엔진의 연소 성능 향상을 위해 연료 분사 타겟팅의 최적화를 수치 해석적으로 연구하였다. 연구에 적용된 연소모델은 ECFM-3Z모델을 사용하였고, 해석에 필요한 엔진 부하 및 연료의 타겟팅은 분사량, 분사각도, 분사시기를 변경하여 해석한 실린더압력, 열 발생률, 배기 배출물 특성의 결과를 비교 분석하여 연구하였다. 연구결과, 분사시기와 분사각도에 따라 연료가 피스톤 보울 안쪽으로 많이 유입될수록 열 발생률의 증가로 인하여 $NO_x$는 증가하였고, CO, Soot은 연소성능의 증진으로 감소하는 것을 확인할 수 있었다. 또한, 분사시기가 진각될수록 균일 혼합기 형성시간이 충분하여 연소성능이 증진되고, 실린더압력은 증가하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.744-752
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• 2007

Recently a fuel oil of the diesel engine in the ship is being changed with low quality as the oil price is higher more and more. Therefore the wear and corrosion in all parts of the engine like cylinder liner ring groove of piston crown, spindle and seat ring of exhaust valve are increased with using of heavy oil of low quality In particular the degree of wear and corrosion in between valve spindle and seat ring are more serious compared to the other parts of the engine due to operating in severe environment such as the high temperature of exhaust gas and repeating impact. Thus the repair weld to the valve spindle and seat ring is a unique method to prolong the life of the exhaust valve in an economical point of view In this study. corrosion property of both weld metal zone and base metal was investigated with some electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram and polarization resistance etc. in 5% $H_2SO_4$ solution. in the case of being welded with some welding methods and welding materials to the exhaust valve specimen as the base metal. In all cases. the values of hardness of the weld metal zone were more high than that of the base metal. And their corrosion resistance were also superior to the base metal. The weld metal of A2F(AC SMAW: 2 pass welding with foreign electrode) showed a relatively good results to the corrosion resistance as well as the hardness compared to the ether welding methods and welding materials. Moreover it indicated that hardness of the weld metal by the domestic electrode was considerably high compared to that of the foreign electrode.

• 한국가스학회지
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• 제20권2호
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• pp.10-15
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• 2016

이 논문의 목적은 자동차 에어컨 가스 누설에 관련된 고장사례를 분석하고 고찰한 것이다. 첫 번째 사례는 냉매가 누설된 상태에서 에어컨 컴프레서가 계속 작동되었다. 이로 인해 에어컨 컴프레서 내부의 피스톤이 윤활부족으로 인해 피스톤이 부분적으로 에어컨 컴프레서 내부의 실린더에 소착되는 현상이 발생하였다. 이것이 엔진작동 중 부하를 증대시켜 엔진의 회전수 변동과 함께 엔진의 작동이 정지되는 현상이 발생된 것으로 확인되었다. 두 번째 사례는 에어컨 라인과 관련 시스템을 확인한 결과 에어컨 컴프레서에서 뒤쪽으로 가는 컨덴서 고압파이프에서 미세한 균열에 의해 에어컨 냉매 가스가 누설되는 것을 확인하였다. 세 번째 사례는 에어컨 컨덴서 핀 부에서 육안으로 확인하기 어려운 미세한 크랙에 의해 컨덴서 내부 안쪽에서 에어컨 가스가 미세하게 누설되는 것을 확인하였다. 따라서, 에어컨 시스템은 에어컨 냉매가스에 의해 자동차의 실내의 온도를 낮춰 공기조화를 하는 시스템이므로 최적의 상태를 유지할 수 있도록 철저한 관리를 하도록 하여야 한다.

• 한국표면공학회지
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• 제31권1호
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• pp.12-23
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• 1998

The Thermal Barrier Coating(TBC) has been used to improve the heat barrier and tribological properties of the aircraft engine and the automobile engine in high temperature. Especially, the high temperature tribological propertied of the cylinder haed and the piston crown of diesel engine was emphasized. Therefore, the purpose of this work was to evaluate the microstructure, tribological propeer in high tempearmal shock resistance and bonding strength of five layer functionally gradient TBC for the applications. The five layerwere composed with 100% ceramic insulating later, 75(ceramic):25 (metal) layer, 50:50 layer, 25:75 layer and 100% metal bonding layer to redude the thermal stress. the YSL and MSL poweders were the insulation ceramics powers. The NiCrAly, Inconel625 and SUS powders were the bonding and mixingg powders for plasma spray process. According to the result of high temperature wear test, the wera resistance of YSZ/NiCrAlY siytem was most out standing at 600 and $800^{\circ}C$. At $400^{\circ}C$, the wear resistance of YSZ/Inconel system was better than others. Wear volume at other temperature because of the low temperature degration of zirconia. The thermal shock mechanism of 5 later is the vertical crack gegration in insulating layer. this means that the initial cracks were generated in the top layer, and then developed into the composite layers during thermal shock test. Finally, these cracks werereached to the interface of coating and substrate and also, these vertioal cracks join with the horizontal cracks of the each layers. The bonding strength of YSZ/NiCrAlY and YSZ/Inconel 5 layer system is better than other 5layer systems. The theramal shock resistance of thermal barrier coating s with 5 layer system is better than that of 3 layers and 2 layers.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.66-73
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• 2005

Hydrogen linear power system is estimated as the next generation power system which can obtain a performance as same as fuel cell. In order to develop Hydrogen combustion power system with high thermal efficiency, it is very important to understand the basic characteristics of hydrogen combustion and establish combustion stabilization technique of its system. In this study, RICEM(Rapid Intake Compression Expansion Machine) for researching of hydrogen combustion linear power system was manufactured and evaluated, and the basic characteristics of linear RICEM were analyzed.

• 설비공학논문집
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• 제15권6호
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• pp.502-509
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• 2003

This paper describes a detailed experimental investigation of heat transfer in a reciprocating rectangular channel fitted with rib structures with particular reference to the design of a piston for marine propulsive diesel engine. The parametric test matrix involves Reynolds number, reciprocating frequency, and reciprocating radius, respectively in the ranges, 1,000～6,000, 1.7～2.5 Hz, and 7～15 cm with four different rib arrangements. The rib arrangements have considerable influences on the heat transfer in the reciprocating channel due to the modified vortex flow structure. The experimental data confirm that the increases in the heat transfer can be seen in order of Case (b), Case (c), Case (d), and Case (a).

• Journal of applied mathematics & informatics
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• 제8권1호
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• pp.165-180
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• 2001

This paper presents a new difference scheme for numerical solution of stiff system of ODE’s. The present study is mainly motivated to develop an absolutely stable numerical method with a high order of approximation. In this work a double implicit A-stable difference scheme with the sixth order of approximation is suggested. Another purpose of this study is to introduce automatic choice of the integration step size of the difference scheme which is derived from the proposed scheme and the one step scheme of the fourth order of approximation. The algorithm was tested by means of solving the Kreiss problem and a chemical kinetics problem. The behavior of the gas explosive mixture (H₂+ O₂) in a closed space with a mobile piston is considered in test problem 2. It is our conclusion that a hydrogen-operated engine will permit to decrease the emitted levels of hazardous atmospheric pollutants.

• Journal of Advanced Marine Engineering and Technology
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• 제27권5호
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• pp.600-608
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• 2003

This Paper describes a detailed experimental investigation of heat transfer in a reciprocating smooth rectangular duct having only the bottom wall heated with reference to the design of a piston for a marine propulsive diesel engine The Parametric test matrix involves Reynolds number and reciprocating radius, respectively, in the range of 1.280∼4.100, and 7∼15 cm with five different reciprocating frequency tested. namely. 1.7, 2.2, and 2.6 Hz. The effects of three different hemi-triangular wavy type tapers on the heat transfer in the reciprocating rectangular channel using the air as a working fluid were check out. The present work confirms that the Nusselt number in the channel with the triangular wavy type taper is lower than without the triangular wavy type taper.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1335-1340
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• 2004

Due to the distinct advantages of comfort, drive ability and fuel economy standard, the variable displacement swash plate type compressor which can control the compressor displacement by increasing or reducing the swash plate angle has been developed for automotive air-conditioning system. That can be obtained constant temperature of car room on the variation cooling capacities or engine speeds. This paper was carried out the analysis of swash plate behavior to obtain the forces and moments applied to the swash plate and to get the variable controlability on the variation of compressor speeds and swash plate chamber pressures. The results of simuation agree very well with the experimental data.