• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.306-313
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• 2005

The performance of a regenerative pump is affected by many parameters, especially blade shape of impeller, leakage flow in the clearance and head losses at the inlet & outlet. An impeller with J-shape blade was designed and 5 times scale up model was tested at similarity conditions to evaluate the performance. Performance variations with clearance change were executed. The amounts of leakage flow through the clearance were estimated using the one-dimensional leakage flow models and analysis. Main leakage flow is generated through the gap between the impeller and casing. The inlet & outlet head losses were also estimated. Such corrections are very important to evaluate the final performance of the impeller and pump. Cavitation test was also performed at 1,200 rpm. NPSH of the regenerative pump was obtained and growth of cavity within blades was visualized.

• International Journal of Fluid Machinery and Systems
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• v.3 no.1
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• pp.29-38
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• 2010

This paper presents a procedure for the design optimization of a centrifugal compressor. The centrifugal compressor consists of a centrifugal impeller, vaneless diffuser and volute. And, optimization techniques based on the radial basis neural network method are used to optimize the impeller of a centrifugal compressor. The Latin-hypercube sampling of design-of-experiments is used to generate the thirty design points within design spaces. Three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model are discretized by using finite volume approximations and solved on hexahedral grids to evaluate the objective function of the total-to-total pressure ratio. Four variables defining the impeller hub and shroud contours are selected as design variables in this optimization. The results of optimization show that the total-to-total pressure ratio of the optimized shape at the design flow coefficient is enhanced by 2.46% and the total-to-total pressure ratios at the off-design points are also improved significantly by the design optimization.

• The KSFM Journal of Fluid Machinery
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• v.3 no.1 s.6
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• pp.19-27
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• 2000

A numerical study is presented for analysis of three-dimensional incompressible turbulent flows in a multi-blade centrifugal fan. Reynolds-averaged Navier-Stokes equations with a standard $k-{\espilon}$ turbulence model are discretized with finite volume approximations. The computational area is divided into three blocks; inlet core, impeller and scroll parts, which are linked by a multi-block method. The flow inside of the fan is regarded as steady flow, and the mathematical models for the impeller forces were established from a cascade theory and measured data. Empirical coefficients are obtained comparing between computational and experimental results for the case without scroll, and are employed to simulate the flow through the impeller with scroll. In comparisons with experimental data, the validity of the mathematical models for the impeller forces was examined. The characteristics of the flow in the scroll were also discussed.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1147-1155
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• 2002

Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m$^3$/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the non-uniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.167-173
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• 2010

In this study, flow structure in a three-stage centrifugal compressor for LNG Plant with the refrigerant, Propane, was numerically investigated at the design point of the compressor using a commercial code. Flow characteristics in the passages of impeller and vaneless diffuser were analyzed in detail including velocity vector, Mach number and pressure contours in blade spanwise and meridional plane for each stage. The estimation on the one-dimensional output from the preliminary design and three-dimensional shape of the impeller blade was performed through the flow analysis. The verification for designed compressor was carried out from three-dimensional Navier-Stokes analysis. The results will be used as reference data for a new design of 3-D impeller shape to improve propane refrigerant compressor performance.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.151-157
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• 1999

In this study, tile characteristics of three dimensional flow fields in centrifugal flump impeller are investigated by numerically. Detailed analysis and understanding of flow field in centrifugal pump are very important to predict performance of components. The three dimensional viscous fluid flow in centrifugal pump is distingushed isentropic process region from irreversible process region by wall shear effect, secondary flow, centrifugal and Coriolis forces, variation of boudary layers. Development of low momentum region by viscous fluid flow in the centrifugal impeller causes stall and blockage which is irreversible process region, and resulting in decrease of the performance and efficiency of centrifugal pump. Especially, the result is that Coriolis and centrifugal forces are most powerful factors which are increasing the irreversible region.

• The KSFM Journal of Fluid Machinery
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• v.2 no.3 s.4
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• pp.17-23
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• 1999

In the present numerical analysis, investigation of the effect of blade loadings from design shape on the slip factor variation was studied. Both the Eckardt radial bladed impeller and the backswept impeller were analyzed. In addition, a new design of the blade profile was arbitrarily attempted to generate a center-loading pattern in the original backswept impeller. Three dimensional compressible Navier-Stokes flow analysis with the Baldwin-Lomax turbulence model was applied to get the numerical slip factor at each impeller exit plane using the mass-averaging technique. The numerical slip (actors are in good agreement with the experimental ones and the Wiesner's slip factors deviate further from the numerical and experimental ones in both backswept impellers. Deviation angles and meridional channel loadings are found in no relation with the trend of change of the slip factor. Blade-to-blade loadings in midspan location are, however, found to have a direct relationship, especially at the sections where maximum loadings we to be expected. That information can be utilized in establishing an improved expression for slip factors in the future.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.113-119
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• 2001

Interaction of flow through an Impeller and a Vaned Diffuser in Centrifugal Compressor was investigated using the 3-dimensional Wavier-Stokes solution method. To consider the interaction effect of impeller and vaned diffuser, Inlet boundary conditions are imposed with the results of the steady calculation of the impeller and rotates with time. The results have been compared to steady computation results and experiment. From this, it is discussed about the compatability of the method and the advantage and disadvantage of the steady calculation.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.217-222
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• 1998

CSCM upwind flux difference splitting compressible Navier-Stokes method has been used to predict the transonic flows in centrifugal compressor diffuser. The modified cyclic TDMA and the mass flux boundary conditions were used as boundary conditions of the diffuser analysis. With the mass flux boundary condition and the $130{\times}80{\times}40$ grid, the compressible upwind Navier-Stokes method predicted the transonic diffuser flowfield successfully. Plow changes in the impeller exit region due to the strong interaction between impeller exit and vaned diffuser, broad flow separation on the suction surface near hub and shroud was observed from the results of the mass flow rates 6.0 and 6.2kg/s at 27000 rpm. The static pressure increased and the total pressure decreased through the flow passage of the channel diffuser, which were predicted better from the three-dimensional analysis than from the two-dimensional analysis due to the strong effect of the three-dimensional flow. The mass averaged loss coefficients and pressure coefficients were also studied.

• International Journal of Fluid Machinery and Systems
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• v.3 no.3
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• pp.260-270
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• 2010

Reducing the losses of the tip clearance flow is one of the keys in an unshrouded centrifugal compressor design and development because tip clearances are large in relation to the span of the blades and also centrifugal compressors produce a sufficiently large pressure rise in single stage. This problem is more acute for a low flow high-pressure ratio impeller design. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range low flow coefficient centrifugal compressor is a great challenge. This paper describes a recent development of high efficiency and wide surge margin low flow coefficient centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in the centrifugal compressor design. The compressor has three main parts: impeller, a low solidity diffuser and volute. The tip clearance is under a special consideration in this design to allow impeller insensitiveness to the clearance. A patented three-dimensional low solidity diffuser design method is used and applied to this design. The compressor test results demonstrated to be successful to extend the low solidity diffusers to high-pressure ratio compressor. The compressor stage performance showed the total to static efficiency of the compressor being about 85% and stability range over 35%. The test results are in good agreement with the design.