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허중식,황영규,김동권,Heo, Jung-Sik,Hwang, Yeong-Gyu,Kim, Dong-Gwan 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.5
Pumping performances of a helical molecular drag dump(MDP) and of a radial MDPs are numerically analyzed by using the direct simulation Monte Carlo (DSMC) method. A helical- and radial-MDP have rotating pumping channels cut on a cylinder and on a disk, respectively. For a helical MDP, the present results agree quantitatively with the previously known numerical results. For radial MDPs, both of the Type 1 (having pumping channels cut on the stationary disk) and of the Type 2 (having pumping channels cut on the rotating disk) are analyzed to predict their performances for various parameters, i.e., the radius of curvature center of the channel wall, the depth of the channel, the clearance between housing and disk, and the rotating speed. The results show that the performance of the Type 2 is superior to that of the Type 1, and that for all types the pumping efficiency decreases as the clearance increases. Also, the radial type MDP has larger leakage losses in the direction of pumping channel than does the helical one.
허중식(Joong-Sik Heo),황영규(Young-Kyu Hwang),박종윤(Chong-Yun Park) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.2
하이브리드형 분자펌프를 구성하고 있는 원판형의 드래그펌프에 대하여 DSMC 수치해석을 이용한 성능해석을 수행하였다. 원판형위에 형성되어 있는 유로상의 기체유동은 3차원의 분자천이영역에 놓이게 된다. 상대적회전좌표계를 택하였기 때문에 분자 각각은 직선적이 아닌 곡선운동을 하게 된다. 따라서 본 연구에서는 코리올리스힘과 원심력을 포함한 미분방정식을 적분함으로써 분자 개개의 곡선궤적을 구하였다. 수 치해석시 분자충돌과정은 null-collision기법과 VSS(variable soft sphere)모델을 이용하여 계산하였으며, 이전의 선행연구와 비교한 결과 큰 차이를 보여주었다. 이것은 출구로 부터의 분자들의 역류에 의해 펌핑유로가 매우 제한되어지기 때문이며, 이러한 현상은 기존연구에서는 나타나지 않았다. Pumping performance of a disk-type molecular drag pump for a hybrid molecular pump is numerically analyzed by the direct simulation Monte-Carlo method. The flows in pumping channels are three-dimensional (3D) in a molecular transition regime. The main difficulty in modeling a 3D case comes from the rotating frame of reference. Thus, trajectories of particles are no longer straight lines. In the present study, trajectories of particles are calculated by integrating a system of differential equations including the Coriolis and centrifugal forces. The null-collision technique with a variable soft sphere molecular model is used for calculation of molecular collisions. The present numerical results significantly disagree with the previously known ones. This indicates that an actual pumping passage is very limited to a narrow region due to the significant backstreaming of molecules from the outlet.