• Title, Summary, Keyword: Piston crevice volume

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Piston Crevice Hydrocarbon Oxidation During Expansion Process in an SI Engine

  • Kyoungdoug Min;Kim, Sejun
    • Journal of Mechanical Science and Technology
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    • v.17 no.6
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    • pp.888-895
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    • 2003
  • Combustion chamber crevices in SI engines are identified as the largest contributors to the engine-out hydrocarbon emissions. The largest crevice is the piston ring-pack crevice. A numerical simulation method was developed, which would allow to predict and understand the oxidation process of piston crevice hydrocarbons. A computational mesh with a moving grid to represent the piston motion was built and a 4-step oxidation model involving seven species was used. The sixteen coefficients in the rate expressions of 4-step oxidation model are optimized based on the results from a study on the detailed chemical kinetic mechanism of oxidation in the engine combustion chamber. Propane was used as the fuel in order to eliminate oil layer absorption and the liquid fuel effect. Initial conditions of the burned gas temperature and in-cylinder pressure were obtained from the 2-zone cycle simulation model. And the simulation was carried out from the end of combustion to the exhaust valve opening for various engine speeds, loads, equivalence ratios and crevice volumes. The total hydrocarbon (THC) oxidation in the crevice during the expansion stroke was 54.9% at 1500 rpm and 0.4 bar (warmed-up condition). The oxidation rate increased at high loads, high swirl ratios, and near stoichiometric conditions. As the crevice volume increased, the amount of unburned HC left at EVO (Exhaust Valve Opening) increased slightly.

Extension of Backfire Limited Equivalence Ratio in Hydrogen Engine by Using Multi Point Ignition Method (다점점화에 의한 수소기관의 역화발생 억제효과에 관한 검토)

  • Kim, Y.Y.;Lee, C.W.;Lee, Jongtai
    • Transactions of the Korean hydrogen and new energy society
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    • v.14 no.2
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    • pp.131-137
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    • 2003
  • Backfire occurrence must be controlled for the practical use of hydrogen fueled engine. It was found from preceeding studies that crevice volume around piston rings could effect a backfire occurrence. In this study, a possible countermeasure to backfire occurrence was evaluated by using multi point ignition method around piston ring. The results showed that backfire limited equivalence ratio was increased by a little due to a enhancing effect of mixture combustion around piston crevice volume.

Study on Backfire for a Two-Stroke Hydrogen Fueled Free-Piston Engine with Loop Scavenging (루프소기방식을 갖는 2행정 프리피스톤 수소기관의 역화에 관한 연구)

  • Cho, Kwan-Yeon;Byun, Chang-Hee;Back, Dae-Ha;Lee, Jong-Tae
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.6
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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.

A Basic Study on Piston-Ring Pack (피스톤-링 팩에 관한 기초 연구)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.21 no.2
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    • pp.83-92
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    • 2005
  • A piston assembly is very important because it directly receives the energy generated during combustion process. Surely, the friction and lubrication of piston-ring pack do an important role in the performance and fuel economy of an engine. In fact, the friction loss in piston-ring pack is the biggest portion to the whole engine friction. Therefore, the improvement of lubrication quality and friction loss in piston-ring pack will be directly related with the improvement in the performance and fuel economy of an engine. Meanwhile, the oil consumption and blow-by gas through piston-cylinder-ring crevices have to be controlled as less as possible. In these two aspects, the study on the optimized design of piston-ring pack has to be carried out. In this study, for the efficient design of piston-ring pack, it is focused to develop a basic computer program that predicts the inter-ring pressure, the motion of ring and the blow-by gas through a crevice volume model between adjacent rings, and the oil film thickness and the friction computed by lubrication theories.

The Characteristics of Backfire for 2 stroke Free-Piston Hydrogen Fueled Engine with Uni-flow Scavenging (Uni-flow 소기방식 2행정 프리피스톤 수소기관의 스트로크변화에 따른 역화 특성)

  • Cho, Kwan-Yeon;Cho, Hyung-Wook;Lee, Jong-Tae
    • Transactions of the Korean hydrogen and new energy society
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    • v.20 no.5
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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.

A Study on Oil Consumption Related with the Piston Ring Pack with Thinner Ring Width and Lower Ring Tension (박폭 저장력 피스톤 링 팩에 대한 오일소모 연구)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.25 no.5
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    • pp.311-317
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    • 2009
  • To satisfy the more severe emission regulation and the demand of higher fuel economy in near future, the combustion pressure and power output of engines is going to be higher. In order to get the reduction of engine emission and the higher power, it is needed the reduction of the tension and width of ring pack. The lower tension ring and the thinner width ring can bring not only the friction reduction between the ring and liner during engine running, but also the adjustment of the blow-by gas and oil consumption by changing in the pressure in the crevice volume and the axial motion of rings togethe with the adjustment of the inter-ring crevice volumes. In this study, by using a developed basic computer proglram that predicts the blow-by gas and oil consumption of engines, it is to be examined how satisfying the level of the blow-by gas and oil consumption as being installed the piston ring pack with thinner width ring and lower tension ring.

Development of a Basic Program for the Study of Piston-Ring Pack (피스톤-링 팩 연구를 위한 기초 프로그램 개발)

  • Chun Sang Myung;Ha Dae-Hong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.149-157
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    • 2004
  • A Piston assembly is very important because it directly receives the energy generated during combustion process. Surely, the friction and lubrication of piston ring pack do an important role in the performance and fuel economy of an engine. in fact, the friction loss in piston ring pack is the biggest portion to the whole engine friction. Therefore, the improvement of lubrication quality and friction loss in piston ring pack will be directly related with the improvement in the performance and fuel economy of an engine. Meanwhile, the oil consumption and blow-by gas through piston-cylinder-ring crevices have to be controlled as less as possible. In these two aspects, the study on the optimized design of piston ring pack has to be carried out. In this study, for the efficient design of piston ring pack, it is focused to develop a basic computer program that predicts the inter-ring pressure, the motion of ring and the blow-by gas through a crevice volume model between adjacent rings, and the oil film thickness and the friction computed by lubrication theories.

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A Study on the Backfire and Abnormal Combustion in the Free-piston Hydrogen Fueled Engine (프리피스톤 수소기관의 역화 및 이상연소에 관한 연구)

  • Kim, K.M.;Park, S.W.;Lee, J.H.;Noh, K.C.;Lee, J.T.;Lee, Y.K.
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.1
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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.

A Study on Friction Reduction Related with the Piston Ring Pack with Thinner Width Ring and Lower Tension Ring (박폭 저장력 피스톤 링 팩에 대한 마찰저감 연구)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.25 no.5
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    • pp.348-358
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    • 2009
  • To satisfy the more severe emission regulation and the demand of higher fuel economy in near future, the combustion pressure and power output of engines is going to be higher. In order to get the reduction of engine emission and the higher power, it is needed the reduction of the tension and width of ring pack. The lower tension ring and the manufacturing technology of cast iron thinner width ring can bring the friction reduction between the ring and liner during engine running. Therfore, the fuel economy can be achieved. Thereafter the engine emission can be reduced. In this study, by using a developed basic computer program that predicts the inter-ring pressure, the motion of ring and the inter-ring pressure through a crevice volume model between adjacent rings, and the oil film thickness and the friction computed by lubrication theories, it is to be examined the effect of friction reduction from piston ring pack equipped with thinner width ring and lower tension ring.

A Study on the Combustion Stabilization and Performance Improvement in the Free-piston Hydrogen Fueled Engine (프리피스톤 수소기관의 연소안정화 및 성능향상에 관한 연구)

  • Noh, K.C.;Yoon, J.S.;Kim, K.M.;Park, S.W.;Lee, J.T.
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.2
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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.