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RISS 인기검색어
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- 저자 : 이경환(K. H. Lee) (검색결과 48 건)
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SI 엔진의 밸브 리프트에 따른 흡입 포트 및 실린더내 정상 3차원 유동장 해석
김영남(Y. N. Kim),이경환(K. H. Lee) 한국자동차공학회 1995 한국 자동차공학회논문집 Vol.3 No.5
The three-dimensional fluid motion through the intake port and cylinder of a single DOHC SI engine was investigated with a commercial computational fluid dynamics simulation program, STAR-CD. This domain includes the intake port, intake valves and combustion chamber. Steady induction port flows for various valve lifts have been simulated for an actual engine configuration. The geometry was obtained by direct interface with a three-dimensional CAD software for complicated port and valve shape. The computational grid was generated using the commercial preprocessor ICEM CFD/CAE. Detailed procedures were presented on the generation of the geometry and the block-structured mesh.<br/> A standard k-.s turbulent model was applied to consider the complexity of the geometry and the fluid motion. The global flow patterns and the distributions of various quantities, such as pressure, velocity magnitude around the valve seat etc., were examined. The computational results, such as mass flow rate, discharge coefficient etc., for various valve lifts were compard with the experimental results and the computational results were found in good agreement with the experiment.
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고받음각에서 프렁잉(Plunging) 진동하는 날개 주위의 아음속 유동해석
이경환(K.H. Lee),김재수(J.S. Kim),전승배(S.B. Jun) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
Many numerical and experimental researches have been done for the flow around oscillating airfoils. The main research topics are wake vortex shading, dynamic stall phenomenon, MAVs lift and thrust generation, et.al. Until now, researches mainly have been concentrated to analyze the wake flow for the variation of frequency and amplitude at a low angle of attack. In this study, wake structures and acoustic wave propagation characteristics were studied for pure harmonic plunging oscillating airfoil at a high angle of attack. The governing equations are the Navier-Stokes equation with LES turbulence model. OHOC (Optimized High-Order Compact) scheme and 4th order Runge-Kutta methods were used. The Mach number is 0.3,the Reynolds number is 1.0×10<SUP>5</SUP>,and the angle of attacks are 20° ~ 50°. The plunging frequency and the amplitude are from 0.05 to 0.15, and 0.1?0.2, respectively. Because of the high resolution numerical methods, wake vortex shedding and pressure wave propagation process, as well as the propagation characteristics of acoustic waves can be simulated. The results of frequency analysis show that the flow has the mixed characteristics of the forced plunging frequency and the nature vortex shedding frequency at a higt angle of attack.
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이경환(G. H. Lee),심규진(K. J. Shim),이용훈(Y. H. Lee),정한식(H. S. Chung),정효민(H. M. Jeong) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The study about hydrogen fuel which consist of hydrogen extraction and reforming process, fuel cell equipment, and receptacle are flourishing all over the world. Currently, Korean hydrogen station is still underdeveloping. And also the most important part which is hydrogen compressor has not been developed. Snubber is one of the most important parts inhydrogen compressing system. It has installed reciprocating hydrogen compressor. One of these components is snubber which has function to reduce pulsation waveform and to remove the impurities in the hydrogen gas. Therefore, a snubber has a buffer. It is an inclined plate, attached inside snubber. The best snubber is the one which has the least pressure loss and the most pressure amplitude reduction. Furthermore, investigating geometric optimum size of with-buffer snubber has been done by numerical analysis approach.
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이경환(G. H. Lee),악바르(Wanda Ali Akbar),심규진(K. J. Shim),정한식(H. S. Chung),정효민(H. Min Jeong) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The studies about hydrogen fuel which consist of hydrogen extraction and reforming process, fuel cell equipment, and receptacle are flourishing all over the world. But, Korean hydrogen station is still underdeveloping. And also a hydrogen compressor which is the most important part at the hydrogen station, has not been developed. Snubber is one of the most important parts in hydrogen compressing system. Snubber has function to reduce pulsation waveform and to remove the impurities in the hydrogen gas. A snubber has an inclined plate as a buffer, which is installed inside snubber. When the pressure loss and the pulsation of pressure within a snubber is minimized, the snubber could get more applicability. Therefore, a study to find an optimum geometric size on a several snubbers which have different buffer width, has been conducted using a numerical analysis. The numerical results show the special characters of snubber according to various buffer angle. The minimum pressure loss ratio occurs when the buffer angle is 35. and the minimum pressure pulsation ratio occurs when the buffer angle 10.
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4-Valve SI 엔진의 Knock 특성 및 Knock 발생부위 측정
이경환(K. H. Lee),이시훈(S. H. Lee) 한국자동차공학회 1998 한국 자동차공학회논문집 Vol.6 No.5
The knock in a spark ignition engine has been investigated to avoid the damage to the engine and unpleasant feeling caused by the pressure waves propagating across the combus-tion chamber. Knock intensity and knock onset angle were used as physical parameters to quantify the knock characteristics. The knock intensity is defined as - a peak to peak value of the band pass filtered combustion pressure signal and the knock onset angle is determined as the crank angle at which this signal exceeded the threshold level on each cycle. The cyclic variation of knock in a four valve single cylinder engine was investigated with these two parameters.<br/> The location of autoignition was also examined by ion probes in the cylinder head gasket and squish region in the combustion chamber. For this measure -ment, a single cylinder engine was modified to accept the pressure transducer, 18 ion probes in the squish region and 8 ion probes in the specially designed PCB (Printed Circuit Board) cylinder head gasket.<br/>
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