• 한국수소및신에너지학회논문집
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• 제19권3호
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• pp.182-188
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• 2008

In order to improve scavenging performance of free piston hydrogen fueled engine, this study estimate compatibility of uni-flow scavenging. The scavenging flow characteristics in the cylinder is investigated by flow visualization and PIV method. Consequently it has been found that the scavenging performance decreased with abnormal expansion of piston and delay of the exhaust valve opening timing. And the scavenging performance of exhaust valve located center in cylinder head is better than that of exhaust valve located side in cylinder head.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.69-79
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• 1997

This paper deals with the measurement and analysis on the scavenging performance of the oppet-valve type two-stroke engine with different shroud system. The scavenging flow characteristics is investigated by flow visualization under steady condition, in which a dye is introduced into single-cycle method using the difference of specific gravity between two working fluids is used to evaluate the scavenging efficiency and the trapping efficiency. The 90° shroud system was found to be the highest efficiency system through both flow visualization and single-cycle test, as well as the shroud system to generally be efficient for reducing a short-circuiting flow during scavenging process in a two-stoke engine.

• 한국자동차공학회논문집
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• 제2권5호
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• pp.48-57
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• 1994

The specific power output and thermal effeciency of any two-stroke engine are dependent on its scavenging behavior. Among the many factors which influence on the scavenging process, the cylinder head shape is one of the important factor. Hence in this study three different type models of cylinder head shape which are the cylindrical, the spherical and the arbitrary shape are studied to show the effects of the turbulent scavenging process in the cylinder with one inlet port, two side ports and one exhaust port. A modified version of KIVA-II which strip out of or add planes of cells across the mesh above the piston for flow simulation of two-stroke engine is used. The $k-{\varepsilon}$ turbulent model is used. The results show that the flow in a two-stroke engine cylinder of the spherical head shape among the three different type model is a desirable for efficient scavenging.

• 한국수소및신에너지학회논문집
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• 제19권2호
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• pp.139-144
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• 2008

The focus of this research is that the scavenging aspect of in-cylinder is visualized by the PIV method and its characteristic is analyzed so that the scavenging performance of the free piston hydrogen fueled engine can improve with loop scavenging. As the results, the piston of convex type shows the best scavenging performance among the presented pistons. In case of the abnormal expansion, the scavenging of area between cylinder head and cylinder wall doesn't operate well.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 추계학술대회 논문집(Proceeding of the KOSME 2000 Autumn Annual Meeting)
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• pp.68-81
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• 2000

Many studies for improving a scavenging efficiency have been executed by using simulative manner. This paper addresses to a scavenging process in a uniflow two stroke cycle engine. The Processes are simulated for scavenging pressure variation, after the assessment of turbulent models. The results have shown that employing RNG k-$\varepsilon$ model gave more accurate velocity profiles near the cylinder wall compared with the standard k-$\varepsilon$ model and the charged fresh air has increased with the scavenging pressure increase.

• 한국수소및신에너지학회논문집
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• 제20권5호
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• pp.371-377
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• 2009

Backfire characteristics for hydrogen fueled free piston engine with uni-flow scavenging is investigated with different stroke, exhaust vlave openning timing and fuel-air equivalence ratio by using RICEM (Rapid Intake Compression Expansion Machine) for combustion research of free piston engine. As results, it is found that backfire can be occurred due to slow combustion of unhomogeneous mixture in the piston crevice volume or/and in the cylinder near piston head. And the more stroke of free piston H2 engine with uni-flow scavenging is short the more opening timing of exhaust valve have to be advanced to control backfire.

• 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.

• 연구논문집
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• 통권28호
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• pp.49-58
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• 1998

포핏밸브형 2행정 기관의 소기 시스템 형상 변화에 따른 소기유동 및 소기효율의 개선 효과를 해석하기 위해, 각 흡기포트 형상별 소기 유동 가시화와 소기효율 정량화 연구를 수행하고자 한다. 소기시스템의 형상은 기계연구원에서 독자 개발한 RSSV(Rotatable Shrouded Scavenging Valve)의 슈라우드 각도를 변화시켰으며, 소기 효율 정량화를 위해 정상상태하에서 등유와 착색된 물을 사용한 single-cycle method. 동적모사장치(dynamic simulatior)에서 $CO_2$와 $O_2$가스를 사용한 가스추출법(gas sampling method)을 적용하였으며 실제 기관에서의 소기 효율을 측정하기 위해 압력 선도를 해석하였다. 위 실험들의 결과로부터 $90^circ$슈라우드 밸브가 가장 높은 효율을 가지는 것으로 판명되었으며, 특히 이들 실험방법들은 2행정 엔진 개발에 있어 시간과 비용을 절감하는데 아주 유용한 기법임을 알 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.22-24
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• 2008

This paper presents a numerical model of internal flows in a lubricant supplying and scavenging flow path of an aero-engine lubrication system. The numerical model was built in the General Analysis Software of Aero-engine Lubrication System, GASLS, developed by Northwestern Polytechnical University. The lubricant flow flux, pressure and temperature distribution at steady state were calculated. GASLS is a general purpose computer program employed a 1-D steady state network algorithm for analyzing flowrates, pressures and temperatures in a complex flow network. All kinds of aero-engine lubrication systems can be divided into finite correlative typical elements and nodes from which the calculation network be developed in GASLS. Special emphasis is on how to use combined elements which is a type of typical elements to replace some complex components like bearing bores, accessory gearboxes or heat exchangers. This method can reduce network complexity and improve calculation efficiency. Final computational results show good agreement with experimental data.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.55-63
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• 2003

In a diesel engine, air-fuel mixture formation and ignition delay period have great influence on the performance of engine. Their main factors are combustion chamber shape, fuel injection system. air volume, air flow and so on. So, the combustion process in the cylinder is complex because of many factors which have direct and indirect effects on it. In this study, we take into consideration of scavenging pressure and scavenging temperature that are hewn as the main factor to the combustion process of two-stroke D.1. diesel engine. It is taken a picture of the combustion flame process for combustion chamber of re-entrant type and cylindrical type. So, it is applied to the basis data of combustion chamber design from an image analysis.