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유압 비례제어 솔레노이드 밸브의 스풀형상이 응답특성에 미치는 영향
이기수(Geesoo Lee),김대현(Daehyun Kim),김현철(Hyunchul Kim),성형진(Hyungjin Sung),이현우(Hyunwoo Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Three-dimensional numerical simulations were carried out to investigate the flow dynamic behavior and pressure characteristics of a variable force solenoid (VFS) valve used in automatic transmissions. To visualize the dynamic movement of the spool, a moving mesh with dynamic layering meshes for varying boundary conditions was employed. The reliability of the employed analysis was demonstrated by the comparison between numerical results and experimental data. The modeling of the VFS valve and the notch depth of the delay parts of the spool was taken into account in analysis. The effects of varying the oil temperature on the pressure sensitivity curves and the seal leakage flow rates were investigated. The VFS valve was characterized by determining the variation in the equivalent orifice area (EOA)with the spool displacement. The pressure sensitivity curves were found to be precisely controlled by the relation between the depth and the area of the notch in the range of the characteristic length of the valve.
1-D Nozzle Flow Model을 이용한 DME 인젝터 노즐 홀 설계
이기수(Geesoo Lee),김대현(Daehyun Kim),김현철(Hyunchul Kim),정수진(Soojin Jung) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
The 1-D nozzle flow model was used to design the injector nozzle holes and to obtain the initial spray conditions for di-methyl Ether(DME) in a 3L diesel common-rail system. In order to deliver the same amount of energy to that provided by diesel at low injection pressure, 40 ㎫, the injector for DME needs larger diameters of nozzle holes and SAC volume at same injection period. In addition to, the lift of a needle should be increased, and the diameter should be increased to keep the minimum flow area ratio. Although the vapor pressure of DME is lower than that of diesel, the condition of cavitation inception for DME was delayed due to the decreased injection pressure. DME showed higher discharge coefficients and effective nozzle exit diameters in comparison with diesel owing to low injection pressure and expanded nozzle diameters. Finally, the spray simulations were performed to investigate spray characteristics of the injection for diesel and DME.
엔진 룸 해석을 이용한 프런트 엔드 모듈의 냉각 성능 평가
이기수(Geesoo Lee),허형석(Hyungseok Heo),원종필(Jongphil Won),김종철(Jongcheol Kim),권두혁(Duhyuk Kwon) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The objectives of this paper were to investigate the cooling performance of the newly developed front end module(FEM) for 2,000cc SUV by means of under-hood simulations at IDLE, 50 ㎞/h up-hill and 120 ㎞/h ; in particular, to analyze the effect of the additional designs eq., air guide or air duct in order to diminish reverse flows from engine room at IDLE condition. The proposed analysis has been performed by applying the commercial computational fluid dynamics(CFD) code, UH3D solver with heat exchanger and fan model, to the solution of the 3-D turbulent flow field on the under-hood flow field. UH3D represented fans as 3-D momentum sources defined by three source components and heat exchangers were treated as regions of momentum transfer and heat transfer. With regard to the newly developed FEM, it was shown that module feature with air guide was more effective in improving the cooling performance than it with air duct at lower cost, thanks to prevent heated recirculating flows from engine room at IDLE.
이기수(Geesoo Lee),허형석(Hyungseok Heo),김현철(Hyunchul Kim) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
This paper presents the design of shell and tube heat exchangers with round tubes and spiral enhanced tubes considering a pumping power. Since the pumping power was considered as a design requirement, the more pressure drop, the smaller the mass flow rate from the relation of it. Therefore, the performance of heat exchanger could be optimized under a given condition. The design was carried out to determine friction drop and heat transfer characteristics of spirally enhanced tubes, which have various geometrical parameters, including a spiral number and a spiral angle. The results showd that overall heat transfer coefficient of the spiral tubes(θ<SUB>s</SUB>=60°, N<SUB>s</SUB>=4, d/D<SUB>h</SUB>=1/6) was 3 times more than that of the round tubes in the turbulent flow. Heat transfer rate of the heat exchanger with the spiral tubes of 12 was 443.4W and about 3 times more than that with the round tubes.
사각 웨이브 형상을 갖는 판형 플라스틱 챠지에어쿨러의 방열성능 설계
이기수(Geesoo Lee),허형석(Hyungseok Heo),김현철(Hyunchul Kim),이승주(Seungjoo Lee) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This study had dealt with the heat transfer characteristics of the automotive charge air cooler which had tubes of rectangular wave form. This study compared and investigated the characteristics as the number of tubes, the pitch and depth of the wave form of the tube on the basis of same core size. The proposed analysis was performed by applying the commercial fluid dynamics(CFD) code, Fluent 6.2, to the solution of 3-D turbulent flows of the plastic charge air cooler. It was found out that both heat transfer characteristics and charge air side pressure drop were linearly increased by severity factor for one step of plastic plate charge air cooler. In addition to, heat transfer performance of the plastic plate charge air cooler assembly with 36 steps of tubes was achieved by 6,850㎉/h at design point.