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다단 자동변속기용 유압 비례제어 솔레노이드 밸브의 CFD 해석
이기수(Geesoo Lee),김현철(Hyunchul Kim),성형진(Hyungjin Sung),허형석(Hyungseok Heo),이현우(Hyunwoo Lee) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
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 motional direction and the speed of the spool were taken into account in the modeling of the VFS valve. The results of Model D, which takes into account both leakage and notches, indicate that there is a linear pressure response in the range of valve overlap and that there are smooth pressure control characteristics in the range of the two notches. Although the effects of magnetic materials were not included, the VFS with a spool was shown to have an unavoidable and unique hysteresis. This hysteresis can be minimized or maintained at low levels by adjusting the relation between the notch depth and the characteristic length.
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.
CFD를 이용한 평형공을 가진 자동차 밀폐형 워터펌프의 축추력 특성에 대한 평가
이기수(Geesoo Lee),허형석(Hyungseok Heo),김현철(Hyunchul Kim),나병철(Byungchul Na),오창복(Changbok Oh) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The aim of this paper was to investigate the fluid dynamic behavior of the automotive closed type water pump with balance hole in order to evaluate and justify its overall hydraulic performance and, in particular to analyze the effects of the balance hole on the reduction of hydraulic flow force of it. The analysis has been peformed by applying the commercial computational fluid dynamics(CFD) code, Fluent, to the solution of the 3-D turbulent flow fields of automotive closed type water pump. The reliability of the employed analysis was demonstrated by the comparison between computed result and experimental data. Although, hydraulic head of the closed type water pump with 3㎜ diameter of balance hole decreased by 1.1 %, axial flow force was effectively reduced by 13.3%, comparison of it with no hole at design point.
하이브리드 차량용 배터리계 냉각시스템의 풍량 개선에 관한 연구
이기수(Geesoo Lee),김현철(Hyunchul Kim),허형석(Hyungseok Heo),김성철(Sungchul Kim),원종필(Jongphil Won),권대복(Daebok Kwon) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The aim of this paper was to investigate fluid dynamic behavior characteristics, and effectively to design of air flow rate of the BAT/INV for hybrid electric vehicles (HEV). The BAT/INV for HEV installed in the luggage space of the vehicle and controlled by the battery monitoring system should operated in suitable thermal environmental conditions by means of air supply system. The analysis of the BAT/lNV cooling system has been peformed by applying the computational fluid dynamics (CFD) code, Fluent, to the solution of the 3-D turbulent flow fields. As a results, at design operating condition, air flow rate of the BAT/INV cooling system with the enhanced blower model increased by 30.8%, Q=162. 7 ㎥/h, comparison to it with the base blower model and the efficiency of the blower motor was predicted about 69.0%. In addition to, to minimize pressure loss of the system, the design of the air duct between the BAT/INV was improved.
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(θs=60°, Ns=4, d/Dh=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.
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.