• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.57-61
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• 2020

Cooling by gas helium circulation can be used for various HTS (high temperature superconductor) magnets operating at 20~40 K, and a cryogenic blower is an essential device for circulating gas helium in the cooling system. The performance of the cryogenic blower is determined by various design parameters such as the impeller diameter, the blade number, the vane angle, the volute cross-sectional area, and the rotating speed. The trailing edge angle and the height of impeller vane are also key design factors in determining the blower performance. This study describes the design, fabrication and performance evaluation of cryogenic blower to produce a flow rate of 30 g/s at 5 bar, 35 K gas helium. The impeller shape is designed using a specific speed/specific diameter diagram and CFD analysis. After the fabrication of the cryogenic blower, a test equipment is also developed using a GM cryocooler. The measured flow rates and the pressure differences are compared with the design values at various rotating speeds and the results show a good agreement. Isentropic efficiency is also evaluated using the measured pressures and temperatures.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.337-341
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• 2010

The flow patterns in a stirred tank, 1m in diameter and 1 m in height, were studied using CFX, a commercial computational fluid dynamics program, with the impeller rotation speed, the impeller blade angle and the tank-bottom shape varied and the baffles included or excluded. A vortex was observed in the center of the tank in the absence of the baffles, and the intensity of the vortex increased with increasing the rotation speed. The vortex was considerably reduced in the presence of the baffles. An increase in the blade angle increased the vertical flow and decreased the vortex intensity. The flow in the corners of the tank bottom turned smoother as the tank bottom was varied in shape from flat to round.

• Journal of Institute of Convergence Technology
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• v.4 no.2
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• pp.61-65
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• 2014

Pressure distribution around rotating impeller blades in centrifugal pump has been main issue for design of efficient and high performance automotive water pump. In addition, pressure losses of inlet water pipes should be considered to reduce additional pressure drop and design high performance engine cooling system. In this paper, pressure distribution inside water pump and pressure drop between inlet and outlet of water pump are investigated numerically to design plastic water pump for clean diesel engine application. And the inlet geometry of water pump was considered to analysis the effect of inlet water pipe geometry on pressure distribution around impeller blades and outlet pressure. The prediction results are compared with experimental data to validate and determine optimal operation condition without water pump cavitation. Major design parameters such as blade angle, volute geometry, system pressure, and coolant flow rate are considered to confirm applying possibility of plastic blades to the clean diesel engine.

• International Journal of Fluid Machinery and Systems
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• v.2 no.2
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• pp.127-135
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• 2009

A conventional centrifugal pump causes a drastic deterioration of air-water two-phase flow performances even at an air-water two-phase flow condition of inlet void fraction less than 10% in the range of relatively low water flow rate. Then we have developed a two-phase flow centrifugal pump which consists of a tandem arrangement of double rotating cascades and blades of outer cascade have higher outlet angle more than $90^{\circ}$. In design of the two-phase flow pump for various sized and operating conditions, similarity relations of geometric dimensions to hydraulic performances is very useful. The similarity relations of rotational speed, impeller diameter and blade height are investigated for the developed impeller in the present paper. As the results, the similarity law of rotational speed and impeller diameter is clarified experimentally even in two-phase flow condition. In addition, influences of blade height on air-water two-phase flow performances indicate a little difference from the similarity relations.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.152-155
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• 2008

In this paper, the effect of modification of geometric variables on the performance of a centrifugal compressor blade has been studied numerically. The compressor contains six main blades and six splitter blades. Reynolds averaged Navier-Stokes (RANS) equations with shear stress turbulence (SST) model are discretized by finite volume approximations and solved on hexahedral grids for flow analysis. The design variables from blade lean angle at tip and middle of the blade have been modified. The isentropic blade efficiency and pressure have been predicted with the variation of the variables. Frozen rotor simulation is performed and adiabatic wall condition has been used. One of the six blades of compressor has been used for simulation to reduce the computational load. Optimum number of meshes has been selected by grid-dependency test, and this is used for all the simulations with changing geometric variables. The detailed flow analysis results have been reported as well as the effects of the variables.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.851-856
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• 2003

A cross-flow fan consists of an impeller, a stabilizer and a rearguider. When it applied for an air conditioner, an evaporator should be added. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. Therefore, the performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, 15% by the heat exchanger. At the low flow rate, there are a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. Moreover, the reciprocal relation between the impeller and the flow passage is the important factor for performance improvement of the cross-flow tan because each parameter is independent. The performance characteristics in the cross-flow fan are graphically depicted with various impeller outlet angles and rearguiders.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1457-1463
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• 2003

In this paper, the response surface method using three-dimensional Navier-Stokes analysis to optimize the shape of a multi-blade centrifugal fan, is described. For numerical analysis, Reynolds-averaged Navier-Stokes equations with standard k - c 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 this 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.

• Proceedings of the KSME Conference
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• 2003.04a
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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

• 유체기계공업학회:학술대회논문집
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• 1998.02a
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• pp.128-135
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• 1998

Procedures and results of aerodynamic design of a centrifugal compressor are presented for development of a 40kW class turbogenerator gas turbine. Specification of higher level of total pressure ratio of 4 and total efficiency of $80\%$ requires advanced methods of design and analysis. In the meanline design/analysis, a method with conventional loss modeling and a method with the two-zone model are alternately used for more reliable prediction. In the impeller blade generation, a series of Bezier curve are combined to produce meridional contours and distributions of blade camber angle and blade thickness. Intermediate profiles of blades are repeatedly produced and changed to be finally fixed through quasi-three dimensional Euler flow analysis. Three dimensional compressible turbulent flow analysis is then performed for the impeller to be confirmed in the final step of design. Satisfactory results in the aerodynamic performance are obtained, which assures that there is no need of aerodynamic re-design.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.410-415
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• 2000

Slip factor is defined as an empirical factor being multiplied to theoretical energy transfer for the estimation of real work input of a centrifugal compressor. Researchers have tried to develop a simple empirical model, for a century, to predict a slip factor. However most these models were developed on the condition of design point assuming inviscid flow. So these models often fail to predict a correct slip factor at off-design condition. In this study, we summarized various slip factor models and compared these models with experimental and numerical data at off-design condition. As a result of this study, Wiesner's and Paeng and Chung's models are applicable for radial impeller, but all the models are not suitable for backswept impeller. Finally, the essential avenues for future study is discussed.