• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1640-1645
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• 2004

The pumping characteristics of a single-stage disk-type drag pump ( DTDP ) are calculated,for the variation of the vertical clearance between a rotor and stator and of the radial clearance between a rotor and casing wall, by the three-dimensional direct simulation Monte Carlo (DSMC)method. The gas flow mainly belongs to the molecular transition flow region. Spiral channels of a DTDP are cut on the both the upper and lower sides of a rotating disk, but the stationary disks are planar. As a consequence of results, the vertical and radial clearances have a significant effect on the pumping performance. Experiments are performed under the outlet pressure range of 0.4 $^{\sim}$ 533 Pa. When the numerical results are compared to the experimental data, the numerical results agree well qualitatively.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.561-566
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• 2011

In this paper, 1-D design of axial flow hydraulic turbine including runner blades, spiral casing with distributors(guide vanes and stay vane), and draft tube was conducted and then 3-D flow analysis was carried out using CFX-12.1. The results of 3 runners showed that with an increase in the number of blades, the flow rate and the power of the turbine system increased. On the other hand. the runner loss was not directly connected with the number of blades. As a result, proper blade number could be selected and more than 100kW small hydraulic turbine could be designed.

• 한국전산유체공학회지
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• 제20권3호
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• pp.35-40
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• 2015

Centrifugal pumps consume considerable amounts of energy in various industrial applications. Therefore, improving the efficiency of pumps machine is a crucial challenge in industrial world. This paper presents numerical investigation of flow characteristics in volutes of centrifugal pumps in order to compare the energy consumption. A wide range of volumetric flow rate has been investigated for each case. The standard k-${\varepsilon}$ is adopted as the turbulence model. The impeller rotation is simulated employing the Multi Reference Frames(MRF) method. First, two different conventional design methods, i.e., the constant angular momentum(CAM) and the constant mean velocity (CMV) are studied and compared to a baseline volute model. The CAM volute profile is a logarithmic spiral. The CMV volute profile shape is an Archimedes spiral curve. The modified volute models show lower head value than baseline volute model, but in case of efficiency graph, CAM curve has higher values than others. Finally for this part, CAM curve is selected to be used in the simulation of different cross-section shape. Two different types of cross-section are generated. One is a simple rectangular shape, and the other one is fan shape. In terms of different cross-section shape, simple rectangular geometry generated higher head and efficiency. Overall, simulation results showed that the volute designed using constant angular momentum(CAM) method has higher characteristic performances than one by CMV volute.

• 신재생에너지
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• 제10권4호
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• pp.9-15
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• 2014

In this study pressure and shaft torque pulsation were measured with variation of head and flow during the model test for a 15 MW Francis Turbine. Pressure pulsations were measured at the inlet of the spiral casing and 4 points in the cone of the diffuser and shaft torque pulsation at the upper position of the turbine. The maximum amplitude of pressure pulsation appeared 2.03% of the maximum rated head with the frequency of 25% of the rated revolution and at the guide vane opening of $10^{\circ}$. Shaft torque pulsation appeared 0.01% of the rated shaft torque, fairly low value. Air was admitted through the cone and pressure pulsation gradually decreased with increase of air flow and kept nearly constant after 5% of the rated flow. A new Francis turbine of which specific speed is 115 m-kW had been designed to rehabilitate the old one and the model test was performed at EPFL. The commercial code, STAR-$CCM^+$ was used for numerical simulation of flow.

• 한국유체기계학회 논문집
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• 제18권3호
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• pp.46-52
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• 2015

Pump-turbine system is widely used by the hydropower industry for stabilizing the electrical grid in the vast growing economy of most developed countries. This study only investigates the Fluid-structure Interaction (FSI) analysis of the pump-turbine system at various operating conditions. The FSI analysis can show how reliable each component of the system is by providing the engineer with a better understanding of high stress and deformation points, which could reduce the lifespan of the pump-turbine. Pump-turbine components are categorized in two parts, pressurized static parts and movable stressed parts. The fixed parts include the spiral casing, top and bottom cover, stay vane and draft tube. The movable parts include guide vanes and impeller blades. Fine hexahedral numerical grids were used for CFD calculation and fine tetrahedral grids were used for structural analysis with imported load solution mapping greater than 90 %. The maximum equivalent stress are much smaller than the material yield stress, and the maximum equivalent stress showed an increasing tendency with the varying of operating conditions from partial to excessive at both modes. In addition, the total deformation of all the operating conditions showed a small magnitude, which have quite small influence on the structural stability. It can be conjectured that this system can be safely implemented.

• 한국화재소방학회논문지
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• 제33권3호
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• pp.56-62
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• 2019

본 논문은 규정 유량, 양정, 회전수 및 비속도가 각각 0.7 ㎥/min, 8 m, 1750 rpm, 182 m, ㎥/min, rpm인 원심펌프의 운전시 펌프의 회전수와 유량의 변화가 펌프의 운전특성에 미치는 영향을 고찰하였다. 실험에 사용된 펌프는 안내깃이 없고 외주에 바로 접하여 와류실이 있는 볼류트 펌프를 회전수 1350 rpm에서 1750 rpm까지 100 rpm씩의 회전수 변화 5단계에 따른 H-Q특성, L-Q특성, 𝜂-Q특성 등의 관계와 무차원 성능 특성인 양정계수, 동력계수, 효율 등의 특성을 실험을 통하여 다음과 같은 결론을 얻었다. 회전수의 증가에 따라 펌프 성능의 변화정도를 추정할 수 있고, 펌프의 최대효율은 1450 rpm일 때 유량 0.165 ㎥/min, 양정 4.73 m에서 약 52%, 최대 회전수인 1750 rpm일 때 유량 0.183 ㎥/min, 양정 6.72 m에서 약 50%의 효율이 나타난다. 또한 양정 대 유량의 성능 특성 곡선상에서 등효율 곡선은 펌프의 상사법칙에 따른 원점을 지나는 2차식의 곡선으로 나타나지 않고 타원형으로 변형되어 나타난다. 마지막으로 유량계수가 증가함에 따라 동력계수는 증가하고 양정계수는 감소하며, 유량계수가 0.08일 때 최대효율 52% 되는 것을 통해 유량변화가 운전특성에 미치는 영향을 알 수 있다.