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남윤주(Yun-Joo Nam),박명관(Myeong-Kwan Park) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
This paper is concerned with an electromagnetic design methodology for the magneto-rheological (MR) damper. In order to improve the performance of the MR damper, the magnetic field should be effectively supplied to the MR fluid. Therefore, it is important that magnetic circuit consisting of the MR fluid, the ferromagnetic material for magnetic flux path, and the electromagnetic coil is well designed. For this purpose, two effective approaches are proposed: one is to shorten the magnetic flux path by removing the unnecessary bulk of the yoke in order to improve the static characteristic of the MR damper, and the other is to increase the magnetic reluctance of the ferromagnetic material by minimizing its cross-sectional area through which the magnetic flux passes in order to improve the dynamic and hysteretic characteristics. The effectiveness of the proposed design methodology is verified through magnetic analysis and a series of basic experiments.
남윤주(Yun-Joo Nam),박명관(Myeong-Kwan Park) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The pressure pulsation due to the gear geometry of the gerotor (generalized rotor) pump mainly occurs in the instant that the chamber of the gerotor leaves from the suction port and enters the delivery one. Such a pressure pulsation may result in the undesirable vibration and noise of the pump components as well as the cavitation in the hydraulic system. Therefore, it is very important to examine the pressure characteristic of the gerotor pump at its design and analysis stages. In this paper, in order to reduce the pressure pulsation in the gerotor pump, the port plate with the relief grooves is designed by referring to as the notch of the vane pumps and the relief groove of the piston pumps. A series of the theoretical analyses on the pressure pulsation are performed in consideration of various design parameters of the port plate including the installation positions of the port inlet/outlet and the groove width.
남윤주(Yun-Joo Nam) 유공압건설기계학회 2021 유공압건설기계학회 학술대회논문집 Vol.2021 No.11
본 논문은 작동유 캐비테이션 모델을 고려한 사축식 피스톤 펌프의 특성 해석을 다룬다. 최근, 저자는 사축식 피스톤 펌프/모터의 성능 해석을 위한 해석 코드를 개발했다. 본 연구에서는 해석 코드에 작동유 캐비테이션 모델을 추가한다. 작동유의 밀도와 체적탄성계수는 압력과 온도에 의해 변한다. 특히, 이들은 저압 조건에서 급격하게 감소하는데 이는 작동유에 혼입 또는 용해된 공기량이 증가(aeration)하고 작동유의 증기 압력 이하에서 작동유가 기화(cavitation)되기 때문이다. 피스톤 챔버 압력은 피스톤이 상사점 부근에 위치할 때 고압에서 저압으로 급격히 감소한다. 또한 피스톤 챔버가 흡입 포트를 매우 빠르게 지나갈 때 높은 Mach number 조건으로 인해 작동유가 피스톤 챔버에 충분하게 유입되지 못한다. 이러할 경우, 피스톤 챔버 내 작동유의 aeration 및 cavitation이 발생한다. 결론적으로, 작동유 캐비테이션 모델을 고려한 해석 결과들은 펌프의 작동 메커니즘에 관한 고찰을 효과적으로 제공할 수 있다. This paper presents the characteristic analysis of an axial piton pump considering the cavitation model of the working oil. Recently, the author developed the simulation code for the performance analysis of the swash-plate type axial-piston pump/motor. In this study, the cavitation model of the working oil is added to the simulation code. The density and bulk modulus of the working oil is changed by pressure and temperature. Especially, they are dramatically decreased under low pressure condition since the entrained and dissolved air into the working oil is released (aeration) and the working oil is vaporized below its vaporization pressure (cavitation). The piston chamber pressure is sharply decreased from high pressure and low pressure while the piston is positioned near top dead point. Also, when the piston chamber goes through the suction port very fast, it is not sufficiently filled with the working oil under high Mach number condition. Therefore, the aeration and cavitation of the working oil are occurred inside the piston chamber. Consequently, the simulation results considering the cavitation model can provide the insight for the pump working mechanism effectively.