• Title, Summary, Keyword: 피스톤 틈새체적

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Modeling of Piston Crevice Hydrocarbon Oxidation in SI Engines (전기점화 기관 간극 체적 내 미연탄화수소의 산화 모델링)

  • Choi, Hoi-Myung;Kim, Se-Jun;Min, Kyung-Doug
    • Proceedings of the KSME Conference
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    • pp.884-889
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    • 2001
  • Combustion chamber crevices in SI engines are identified as the largest contributor to the engine-out hydrocarbon emissions. The largest of crevice region is the piston ring pack crevice. To predict and understand the oxidation process of piston crevice hydrocarbons, a 3-dimensional numerical simulation method was developed. A engine shaped computational mesh with moving grid for piston and valve motions was constructed. And a 4-step oxidation model involving 7 species was used and the 16 coefficients in the rate expressions were optimized based on the results from a detailed chemical kinetic mechanism for the oxidation condition of engine combustion chamber. Propane was used as a fuel in order to eliminate oil layer absorption and liquid fuel effect.

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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.

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.

Modification of Balancing Piston for Trimming of Impeller Diameter for Maintaining Axial-Thrust Balance in Low-Specific-Speed Multistage Centrifugal Pumps (저비속도 원심 회전차 외경가공에 따른 축추력 불균형을 감쇄시키기 위한 평형 피스톤 수정방안에 관한 고찰)

  • Yoo, Il-Su;Park, Moo-Ryong;Yoon, Eui-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.9
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    • pp.875-882
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    • 2011
  • In the present study, the imbalance in the axial-thrust and variation in the volumetric efficiency that occurred during the trimming of impeller diameter were investigated. The present study was focused on low-specific-speed multistage centrifugal pumps with a balancing piston as the balancing mechanism. The effects of impeller trimming on the axial-thrust balance in multistage pumps with horizontal and vertical axes were compared. The results showed that impeller trimming resulted in an additional axial-thrust acting in direction of pump inlet. The axial-thrust imbalance due to impeller trimming was more severe in the vertical-axis pumps than in the horizontal-axis pumps. The rate of increase in the diameter of the balancing piston, which was proportional to the rate of impeller trimming, was evaluated to maintain the axial-thrust balance. Furthermore, a simultaneous increase in the piston length and piston diameter was more effective for reducing the axial-thrust imbalance along with the volumetric efficiency drop.

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.

Analysis of Performance Characteristics of Swash-Plate-Type Hydraulic Piston Motor (사판식 유압 피스톤모터의 성능특성 분석)

  • Lee, Yong-Bum;Kim, Kwang-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.11
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    • pp.1441-1446
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    • 2012
  • An axial-piston-type hydraulic motor involves friction and leakage losses at the sliding parts, contact loss at the mechanism assembly parts, volumetric loss caused by the pressure drop, housing oil churning loss and compressibility from the hydraulic oil pipe resistance, etc. the friction and volumetric loss at the hydrostatic bearing between the piston shoe and the swash plate rotating at high speed and having an oil film gap of 8-15 ${\mu}m$ strongly affects the total efficiency of the hydraulic motor. In this study, a variable swash-plate-type hydraulic piston motor operating under a maximum pressure of 35 MPa, maximum speed of 2,500 rpm, and displacement of 320 cc/rev is tested to verify the optimal ratio of the hydrostatic bearing which is closely related to the hydraulic motor performance.