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직동형 릴리프밸브의 오버라이드 저감을 위한 포펫 형상 설계요소 연구
김성원(S. W. Kim),서영민(Y. M. Seo),안현식(H. S. Ahn) 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.6
A direct acting relief valve, of which the override is one of the important issues, is major hydraulic element for controlling pressure and flow in hydraulic actuating systems. Therefore, the research of reducing override of the valve has always been an important topic for decades. Among many design factors of the direct acting relief valve, the shape of the valve poppet is the one that can directly affect the performance the most. Based on previous studies of poppet valve, an actual model is considered as equivalent to the simplified model. The steady flow force acting on the poppet is calculated by momentum theorem applied to the control volume. This paper represents some simulation methods to investigate the flow force effects depending on the shape of the poppet with sharp-edged seat. The result shows that the flow force on poppet is highly affected by inlet/outlet opening areas, poppet tip angle, and poppet plate angle.
시스템 에어컨 실외기 집단 설치 시 에어 가이드가 외부 열적 환경에 미치는 영향
허현(H. Hur),서영민(Y.M. Seo),정명근(M. Jeong),하만영(M.Y. Ha) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.2
The numerical simulations were conducted on thermal environment with group installation of system air-conditioner outdoor unit. In this study, the effect of air-guide on the outdoor unit and consequent the performance improvement of outdoor unit were investigated. To validate the present numerical simulation, the temperature around outdoor units was measured on the real fields where the computational domain is considered in this study. For the numerical simulation, commercial code ANSYS 15.0 was used for the flow solver. Cut-cell mesh method was used for the modeling of the outdoor unit, and Semi-Implicit Method for Pressure Linked Equation(SIMPLE) method was used for pressure and velocity coupling. Detailed performances of outdoor unit were analyzed using the pathline of discharge flow generated from fans of outdoor unit, and the evaluation of performance in the outdoor unit.
굴삭기 냉각시스템 설계 평가를 위한 엔진룸 열유동 해석 검증
이재석(J.S. Lee),서영민(Y.M. Seo),정찬혁(C.H. Jeong),박용갑(Y.G. Park),하만영(M.Y. Ha) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.2
Basically, excavators perform high-load operation in a fixed place on the construction site and the cooling performance of an excavator is determined by a cooling system consisting of heat exchangers and a single fan which are located inside engine room. Therefore, during development of an excavator, it is really important to stably design the cooling system by estimating the heat sources of the excavator. In this study, CFD analysis of the engine room was carried out on four different types of excavators and the results of each CFD analysis were compared with those of the heat balance test. Based on the cooling performance index, which is defined by using the design reference temperature of each heat exchanger, the analysis error rate is up to approximately 10%. As these results, CFD analysis can be used to virtually evaluate excavator cooling performance and to perform design evaluation and verification of the cooling system.