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최영석,김덕수,윤준용,Choi Young-Seok,Kim Deok-Su,Yoon Joon-Yong 한국유체기계학회 2006 한국유체기계학회 논문집 Vol.9 No.4
In this study, the effect of flow settling means on the performance of fan tester were numerically investigated by using a computational fluid dynamics(CFD). The airflow rate was calculated from the pressure differential across a flow nozzle in the measuring plane and the flow settling means were generally installed in the chamber of the fan tester to provide proper airflow patterns ahead of the measuring plane. The predicted nozzle differential pressures with uniform inlet velocities were compared with the values of the ANSI/AMCA 210-99 to verify the performance of the commercial CFD code CFX 5.6. The influence of flow settling means on the measurement of airflow rate in a fan tester were discussed with various porosities and inlet jet velocities. The results obtained show that the proper band of porosities exist to meet the AMCA standard in a specified inlet jet velocity.
날개형상이 프로펠러형 수중믹서의 성능에 미치는 영향에 관한 수치적 연구
최영석,이재환,김상일,Choi, Y. S.,Lee, J. H.,Kim, S. I. 한국유체기계학회 2000 한국유체기계학회 논문집 Vol.3 No.2
In this research, the performance predictions of the submersible mixer were investigated. The variation of the performance characteristics by changing the impeller design parameters were discussed through the flow calculation results by using a commercial program, FLUENT. The performance of the submersible mixers is related to the velocity diffusion profiles downstream of the impeller and also the required input motor power to mix the fluid. In this study, the various design parameters such as the number of blade, the hub and tip diameters, the impeller blade profiles and revolution speed of the blades were taken for the fixed values. The blade sweep direction, the chord length distribution along with the radius of the blade and the inlet blade angle were changed to make different testing models. The flow calculation results show the effect of the changed design parameters on the performance of the submersible mixers and also give some helpful information for designing more efficient submersible mixers.
최영석,심재혁,강신형,Choi, Young-Seok,Shim, Jae-Hyeok,Kang, Shin-Hyoung 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.1
In this study, the performance prediction programs for centrifugal pumps are developed. To estimate the losses in the centrifugal pump impellers, a two-zone model and TEIS(two elements in series) model are applied to the program. The basic concept of a two zone model considers the primary zone that is an isentropic core flow and the secondary zone that has a non-isentropic region at the impeller exit. The flow goes through two different zones and is mixed out at the impeller exit and the mixing process occurs with an increase in entropy, a decrease in total pressure. The level of the core flow diffusion in an impeller was calculated using TEIS(two elements in series) model. The effects of various parameters which are used in this program on the prediction of head and efficiency are discussed. The correlation curves used to select the effectiveness of the primitive TEIS model were suggested according to the specific speed of the centrifugal pumps.
최영석,이용갑,홍순삼,강신형,Choi, Young-Seok,Lee, Yong-Kab,Hong, Soon-Sam,Kang, Shin-Hyung 한국유체기계학회 2001 한국유체기계학회 논문집 Vol.4 No.1
A commercial CFD code is used to compute the 3-D viscous flow field within the impeller of a centrifugal pump. Several preliminary numerical calculations are carried out to determine the influence of the parameters such as the grid systems, the numerical schemes, the turbulence models and the shape of the vaneless diffusers at the design flow rate. The results of the preliminary study are used for the calculation of the off-design flow conditions. The circumferentially averaged results such as the radial and tangential velocities, the exit flow angle, the slip factor, the static pressure and the total pressure are compared with the experimental data at the impeller exit to discuss the influence of the prescribed parameters.
최영석,이경용,이창한,이종훈,Choi, Young-Seok,Lee, Kyoung-Yong,Lee, Chang-Han,Lee, Jong-Hun 한국유체기계학회 2003 한국유체기계학회 논문집 Vol.6 No.2
ADC (Automatic Discharge Connector) is commonly used for the easy maintenance of the submersible pumps. However, the small gap between the flange of the base plate and that of the pipe due to the head rise, the flow momentum change and the mis-installation make a leakage flow that may be a great loss to the pumping system. In this study, the performance degradation was predicted with the simple leakage flow model through the gap. The newly developed ADC was tested, and the leakage performance was compared with the old one and also no-leakage piping system. The newly developed ADC reduced the leakage flow in a satisfactory way in comparison with the old model.
최영석,Choi, Young-Suk 대한전자공학회 1999 電子工學會論文誌-T Vol.t36 No.2
The design method that the structure of double actuators of read-only or read-writable DVD optical pick-up of high density can be compact into the structure of one actuator, is proposed. The designed actuator has the structure of the shaft sliding type in which the moving part can be rotated about the shaft accord to a used optical disc and an objective lens can be switched, and is suspended with magnetic spring. In this actuator, Coulomb's friction is used as damping force and the moving part is designed by finite element method so that the second natural vibration mode can not occur within the servo band. The mock-up of the actuator designed in this paper is made, and its dynamic characteristics is measured and estimated. CD(Compact Disc) 호환성을 가지는 고밀도 재생전용 및 기록재생용 DVD(Digital Video Disc) 기기의 광학픽업 2중 엑츄에이터 구조를 콤팩트하게 할 수 있는 단일 엑츄에이터 설계법을 제시한다. 설계된 엑츄에이터는 가동부에 CD용 대물렌즈와 DVD용 대물렌즈를 함께 장착하고, 사용 디스크에 따라 가동부를 축주위로 회전시켜서 대물렌즈를 전환하는 축습동형 구조를 하고, 자기 스프링에 의하여 부동된다. 감쇠방식으로서는 가동부와 축사이의 쿨롱마찰을 이용하고, 가동부는 유한요소법(FEM)을 통해, 서보대역내에서 2차 진동모드가 발생하지 않도록 한다. 본 논문의 설계법을 검증하기 위하여 시제품을 제작하고, 동특성을 측정, 평가한다.
최영석,이경용,강신형,Choi, Young-Seok,Lee, Kyoung-Yong,Kang, Shin-Hyoung 한국유체기계학회 2003 한국유체기계학회 논문집 Vol.6 No.2
The periphery pump (or regenerative pump) has been generally applied in the automotive fuel pump due to their low specific speed (high heads and small flow rate) with stable performance curves. In this study, the performance prediction of side channel type periphery pumps has been developed. The prediction of the circulatory flow rate is based on the consideration of the centrifugal force field in the side-channel and in the impeller vane grooves. For the determination of performance curve (head-flow rate), momentum exchange theory is used. The effects of various geometric parameters and loss coefficients used in the performance prediction method on the head and efficiency are discussed, and the results were compared with experimental data.