• 한국물환경학회지
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• 제25권5호
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• pp.727-734
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• 2009

This study was carried out to evaluate the high rate biological reactor such as lab scale reactor before the application in site, and to get the basic data for possibility using liquid fertilizer with the effluent from biological reactor when the centrifugal machine was applied. The total volume of this reactor in 6 L, in composted of anoxic reactor (2 L), aerobic reactor (2 L), and nitification reactor (2 L). BOD removal efficiency rates when centrifugal machine was applied after effluent from biological reactor are over than 95%. This biological reactor was required post process to satisfy the effluent standards, and was need centrifugal machine to control the washout of microbes in the reactor. T-N removal efficiency rate in HRT 24 hr with centrifugation is 80.0%, and it is desirable to operate less than $1.3kgN/m^3{\cdot}d$ for 70% of T-N removal efficiency rate. T-P removal efficiency rate in HRT 24 hr is 68.2%, and become higher 71.3% after centrifugation. Considering in the 28.6% T-N removal efficiency rate, the nitrogen contents of the effluent from reactor is 0.34% to satisfy the liquid fertilizer.

• 한국지열·수열에너지학회논문집
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• 제9권3호
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• pp.19-25
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• 2013

A new type axial flow fan with centrifugal sub-blades has been designed and fabricated in the present study. We investigated velocity and pressure distributions in downstream flow fields of the fan experimentally to detect the detailed flow characteristics of new axial flow fan and an existing axial flow fan. Two-dimensional velocity components were probed by applying a particle image velocimetry system and pressure distributions were measured by Pitot tube and micro-manometer. Our results show that the velocity and pressure distributions at the flow fields of the new fan are quite different from the existing fan, and that the centrifugal sub-blades in the new fan can improve the performance characteristics in view of kinetic energy.

• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.688-695
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• 2012

The present study represents the effects of boundary condition on the performance of a centrifugal blower at the interference plane between rotational and stationary domains using three dimensional compressible Navier-Stocks equations. Two boundary conditions, frozen-rotor and stage, are compared to analyze the blower performance. Installation angle between the cutoff of a volute casing and a impeller blade is also introduced to evaluate the blower performance and to understand the internal flow inside the blower. Throughout numerical simulation, it is found that the frozen rotor interface method at the interference plane represents well the variations of flow field inside the blower compared to stage interface method. However, pressure has maximum two percent error according to the installation angles while pressure is almost constant for the stage interface method. And stage interface method can relatively well predict the blower performance. Detailed internal flows of the centrifugal blower are compared and analyzed by numerical simulation.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.326-333
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• 2013

This paper presents the performance enhancement of a double-inlet centrifugal blower by the shape optimization of an inlet duct. Two design variables, a length of anti circulation vane and an angles of inlet guide, are introduced to improve the inlet flow uniformity leading to the blower performance. Three-dimensional Navier-Stokes equations are used to analyze the blower performance and the internal flow of the blower. From the shape optimization of the inlet duct of the double-inlet centrifugal blower, the optimal positions of each design variable are determined. Throughout the analysis of sensitivity, it is found that the angle of the inlet guide is more effective than the length of the anti-circulation vane to increase flow uniformity at the outlet of the duct. Efficiency and pressure for the optimal inlet duct shape are successfully increased up to 3.55% and 3.2% compared to those of reference blower at the design flow condition, respectively. Detailed flow field inside the blower is also analyzed and compared.

• International Journal of Fluid Machinery and Systems
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• 제7권1호
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• pp.28-33
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• 2014

In order to research the relationship between the tip clearance and leakage flow of centrifugal compressor, a high speed centrifugal compressor was investigated by using CFD. A numerical study on the effect of four different rotor tip clearance sizes of centrifugal compressor, which were 0.5times, 1 times, 1.5times and 2.0times of the design tip clearance, was carried out. Efficiency and pressure ratio curves were obtained under different mass flow. The reasons of the clearance vortex and the factors of vortex size were analyzed. The result indicated that with the increase of tip clearance size, the performance of the compressor changed obviously, the performance parameters such as efficiency and pressure ratio tended to decrease obviously. While, the leakage flow does not always lead to leak vortex. The strength of the vortex increased with the tip clearance. The size of leak vortex was affected by the pressure difference between the suction side and the pressure side of blade tip.

• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.57-63
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• 2008

To optimize the stationary components in the multistage centrifugal pump, the effects of the return vane profile on the performances of the multistage centrifugal pump were investigated experimentally, taking account of the inlet flow conditions for the next stage impeller. The return vane, whose trailing edge is set at the outer wall position of the annular channel downstream of the vane and which discharges the swirl-less flow, gives better pump performances. By equipping such return vane with the swirl stop set from the trailing edge to the main shaft position, the unstable head characteristics can be also suppressed successfully at the lower discharge. Taking the pump performances and the flow conditions into account, the impeller blade was modified so as to get the shock-free condition where the incidence angle is zero at the inlet.

• 한국전산유체공학회지
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• 제21권1호
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• pp.58-63
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• 2016

This research is to investigate the performance analysis for efficient design with four different inlet angles of the centrifugal pump impeller. Assuming that the rotation speed and exit angle are fixed, Four cases of the centrifugal pumps were numerically analyzed using ANSYS FLUENT. According to the numerical results, head and pump efficiency at inlet angle of 20 degrees was highest. There is no big difference of efficiency at inlet angle of 20 degrees compared to the inlet angle 30 degrees. About 15% of efficiency at inlet angle of 20 degrees is higher than inlet angle of 40 degrees and 31% higher than inlet angle oof 50 degrees. Because there is liner functional relationship between speed and flow rate, suction flow rate at inlet angle of 20 degrees is superior to the inlet angle of 30 degrees as much as 0.89%, inlet angle of 40 degrees as 13%, inlet angle of 50 as 28.4%. Head at inlet angle of 20 degrees is superior to the inlet angle of 30 degrees as much as 0.4%, inlet angle of 40 degrees as 2.7%, inlet angle of 50 degrees as 3.2%. There should exist highest efficiency and also optimal design shape at inlet angle of 20 degrees.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.174-175
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• 2005

The purpose of this study is focused on the analysis of 3D complex flow and performance characteristics of a centrifugal pump with volute casing. The numerical analysis was performed by commercial code CFX-10 according to the variation of flow rate, which is changing from 5.847$m^3$/min to 6.865$m^3$/min. The rated rotational speed of close type impeller is 1750rpm. Turbulence model, k-${\omega}$ SST was selected to guaranty more accurate prediction of flow separation. The ICEM-CFD 10, reliable grid generation software was also adapted to secure high quality grid generation necessary for the reliable numerical simulation. The experimental results such as static head, brake horse power and efficiency of the centrifugal pump were compared with the numerical analysis results. The simulated results are good agreement with the experimental results less 5$%$ error.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2157-2161
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• 2003

In this paper, the response surface method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan, is described. For numerical analysis, Reynolds-averaged Navier-Stokes equations with standard k-e turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time

• 해양환경안전학회지
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• 제18권5호
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• pp.455-460
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• 2012

이 연구에서는 정사각 단면을 갖는 덕트 내부에 원심력의 영향을 받는 유동의 천이특성을 실험 및 수치적으로 규명하였다. 실험적 연구로서 레이저도플러 속도계를 이용하여 축방향속도를 측정하였고, 상용소프트웨어인 플루언트를 이용한 전산유체 시뮬레이션으로 천이특성을 고찰하였다. 유동의 발달은 딘수와 굽힘각에 의존한다는 사실을 알 수 있었으며 덕트의 중앙에서의 속도분포는 원심력 때문에 내외벽보다 낮은 값을 나타내었다.