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이종범(J. B. Lee),조상훈(S. H. Cho),민병찬(B. C. Min),홍두영(D. Y. Hong),이원주(W. J. Lee) 한국신뢰성학회 2011 한국신뢰성학회 학술대회논문집 Vol.2011 No.6
The failure of LCC analysis is recognized as a serious risk for companies in fast-paced business environment. LCC analysis has been mentioned and analyzed only in accounting perspectives, but recently engineering perspectives of LCC analysis based on the execution of appropriate procedures become more important than the accounting perspectives. Especially, the practical use of reliability engineering related methodologies is recognized as a key factor for the LCC analysis. For the practical use of reliability methods, LCC analysis for unexposed problems is a key issue, and utilizing FMEA and FTA techniques is needed to solve the unexposed problems. Reliability, maintainability, availability, and safety should be evaluated by the LCC analysis with the reliability methods, so we study methodologies for the LCC analysis. Present Worth can be calculated by multiplication of Annual Equivalent Cost and PWAF. Reliability engineering related methods are needed for the process of dividing Present Worth into PWAF, and the practical use of reliability methods can improve accuracy of LCC analysis.
CAVITATION ANALYSIS IN A CENTRIFUGAL PUMP USING VOF METHOD
W.J. Lee(이원주),J.H. Lee(이정현),N. Hur(허남건),I.S. Yoon(윤인식) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.4
Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-ε turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.