• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1037-1038
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• 2007

프리피스톤 기관은 크랭크가 없는 엔진을 동력원으로 리니어 발전기를 구동시켜 전기에너지를 생성하는 시스템으로 기존 왕복 구동식 기관에 비해 기계적 손실이 작고, 팽창 에너지를 최대한 활용할 수 있는 고효율 기관으로 평가되고 있다. 또한 프리피스톤 기관은 가솔린, 디젤, 수소, 천연가스와 같은 청정 연료를 사용할 수 있기 때문에, 최근 에너지 수급 문제 및 대체 에너지원으로 활용할 수 있다는 장점을 가지고 있다. 프리피스톤 기관에 적용되는 리니어 발전기의 경우 기존 회전형 발전기보다 효율은 다소 떨어지는 단점은 있으나, 동력 변환을 하지 않는 리니어 엔진에 적용할 경우에는 효율적 이득을 볼 수 있다. 본 논문에서는 리니어 발전기의 성능 측정을 위한 시험 장치를 구성하고, 프리피스톤용 기관에 적용되는 평판형 및 원통형 타입의 리니어 발전기의 손실 및 효율 특성을 비교하였다.

• 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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• 제17권1호
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• pp.1-7
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• 2006

The free-piston hydrogen fueled engine is estimated as the next generation power system which can obtain high efficiency and low emission, simultaneously. In order to develop the free-piston hydrogen fueled engine, it is necessary to stable the combustion. The engine combustion, backfire and knock phenomenons were studied by using RICEM for researching combustion characteristics of free-piston engine. As the results, backfire occurrence was not observed in the free-piston engine under limited experimental condition. And knocking occurred in case of higher cylinder wall temperature.

• 한국수소및신에너지학회논문집
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• 제17권2호
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• pp.227-233
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• 2006

A free-piston hydrogen fueled engine is considered as one of the next power systems which is able to obtain high efficiency and low emission, simultaneously. In this study, in order to ensure the possibility as the next generation power system, the combustion characteristics and the performance of the free-piston hydrogen fueled engine are analyzed by using the linear RICEM for the change of injection pressure and equivalence ratio. As the results, in-cylinder maximum pressure is shown at injection pressure $P_{inj}$=6bar. Backfire phenomenon is not observed under experimental condition and knock occurs over ${\Phi}=0.8$. The thermal efficiency is the highest at injection pressure, $P_{inj}$=6bar and equivalence ratio, ${\Phi}=0.7$, respectively.

• 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.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.794-799
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• 2011

In order to reduce the oil consumption for a 2 stroke free piston hydrogen fueled engine, the behaviors of residual lubricant oil of the cylinder wall surface were visualized and oil mass emitted into exhaust port was measured by using research engine with cross-head and eccentric crankshaft. As the results, it was shown that characteristics of residual lubricant oil such as oil thickness and distribution were remarkably different from a conventional 4 stroke engine. It was also analyzed that these tendencies relied on the configuration and installed position of the exhaust port, piston pin boss and so on.

• 한국수소및신에너지학회논문집
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• 제14권4호
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• pp.283-290
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• 2003

To clarify the cause of backfire occurrence and realize a hydrogen fueled engine linear alternator system, dynamic characteristics of a free-piston hydrogen engine were analyzed and compared with those of conventional reciprocating engines. It was found that the mean velocity and acceleration of a free-piston engine were higher than those of reciprocating engines. Piston displacement and compression ratio were varied with the change of the fuel mass flow rate. Therefore, the operational stability and controllability were the most important thinks of the development of a free-piston hydrogen engine.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.299-304
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• 2011

A hydrogen fueled 2 stroke free-piston engine with reverse uni-flow scavenging have a advantageous structure for the backfire occurrence, but it can reduce thermal efficiency by the circuit-flow to go through a exhaust-port. In this research, varied boost pressure, SVOT and exhaust pressure are used in a 2stroke free-piston engine with hydrogen fueled for studying the possibility of increasing thermal efficiency of free-piston hydrogen engine. As a result, to increase thermal efficiency of free-piston are suitable to supply the mixture after port closed the exhaust rater than to use the scanvenging. And it was increased by the exhaust pressure, to achieve it must be used the lean-mixture at SVOT aBDC $34^{\circ}$.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.487-492
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• 2010

For developing a two-stroke free-piston hydrogen engine with high efficiency and low emission, determination of the scavenging type is one of the most important factor. In this research, backfire characteristics for loop scavenging were analyzed with the number of piston crevice volume and piston expansion speed. Rapid Compression Expansion Machine, RCEM was used for combustion research of the free piston $H_2$ engine in the experiment. As the results, it was shown that although backfire occurring in a loop scavenging type can be partially controled by a complete exhaust of burned gas, possibility of backfire basically exist due to the structure which piston crevice volumes contact with fresh mixture in a scavenging port. However, a loop scavenging may be considered as combustion chamber of a free piston $H_2$ engine from the point of view that backfire does not occur nearby lean equivalence ratio obtained high thermal efficiency. It was also analyzed that an advances of backfire occurrence timing with increase of the fuel-air equivalence ratio were due to promotion of flame propagation into piston crevice volumes by decrease of the quenching distance.

• 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.