• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.589-596
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• 2006

This study aims to propose a new model axial flow fan which attachs centrifugal blades, and to investigate the effect of centrifugal blades on the performance improvement of new model axial flow fan. A numerical simulation has been conducted using STAR-CD commercial code to solve the three dimensional incompressible Navier-Stokes equation for high Reynolds number $k-{\epsilon}$ turbulent model. Numerical simulation is carried out to investigate the detail phenomenon in the flow field and performance characteristics of new model and normal model fan. Calculation results are compared with normal model's results to investigate which centrifugal blades effect on velocity profile and pressure distribution at various flow field positions. and calculation results show that new model fan can improve the performance of total pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.916-923
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• 2000

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates arc used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady and incompressible. These numerical results are compared with the experimental data inside a rotor and at the fan outlet. Most important flow features are captured through this numerical approach. Finally details of flow field inside a fan are described and analyzed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.28-29
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• 2006

High-Speed Centrifugal Compaction Process (HCP) is a wet compacting method, in which powders are compacted under a huge centrifugal force. The HCP was well applied to small alumina specimens, but the compact easily cracked when we applied the HCP to other materials. We clarified how the cracks introduced and found that the formation of such a flow pattern was related to the Colioli's force in the centrifugal field.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.533-541
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• 2005

Compared to axial compressors, an analytical model capable of analyzing the flow in centrifugal compressor lacks because of the difficulty in governing equations for radial duct. Therefore, this paper presents a new model to predict flow field in a centrifugal compressor with a sinusoidal asymmetric tip clearance. To predict the 2 dimensional flow in the inlet and exit of the centrifugal compressor, the two flow fields are connected with compressor characteristic based on Moore-Greitzer model. Contrary to axial compressors, the nonuniformity of impeller exit pressure in centrifugal compressor decreases as flow coefficient decreases. In addition, that is sensitive to the slope of pressure rise by eccentricity. The maximum velocity exists right before the maximum tip clearance.

• The KSFM Journal of Fluid Machinery
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• v.2 no.3 s.4
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• pp.45-51
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• 1999

Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise due to the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan and to calculate the effects of rotating velocity, flow rate, cut-off distance and the number of blades and its effects on the noise of the fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated with the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The cut-off distance is the most important factor effecting the noise generation. Acoustic pressure is proportional to 2.8, which shows the same scaling index as the experimental result. In this paper, the cut-off distance is found to be the dominant parameter offecting the acoustic pressure.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.36-42
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• 2002

A new method to calculate the aeroacoustic pressure of a centrifugal fan that is used in a vacuum cleaner has been developed. The centrifugal fan consists of the impeller, the diffuser, and the circular casing. Due to the high rotating speed of the impeller and the small gap distance between the impeller and diffuser, the centrifugal fan makes very high noise levels at BPF and its harmonic frequencies. In order to calculate the sound pressure of a centrifugal fan, the unsteady flow field data is needed. This unsteady flow field is calculated by the vortex method. The sound pressure is then calculated by acoustic analogy. In this paper, only dipole term is considered in the equation. The noise generated by moving impeller and stationary diffuser is calculated separately. The predicted acoustic pressures agree very well with the measured data. The difference between the two is less than 4dB

• 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.1 no.1 s.1
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• pp.64-71
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• 1998

The non-uniform pressure generated in the volute generally are propagating upstream. As a result, outlet conditions of rotaing impeller are changed and the performance degrades. The major object of this research is to develop the numerical method which can calculate the effects of impeller and volute flow field interactions. Under the assumption of steady three-dimensional incompressible turbulent flow, the time averaged N-S equations involving $k-{\epsilon}$ turbulent model was solved by the F.V.M. To verify the computational method, the calculations are compared with experimental results published in literature and show satisfactory agreement with them, The three-dimensional flow characteristics within the volute of a centrifugal fan at design and off-design operating points have also been studied.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.174-180
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• 1998

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates are used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady state and incompressible. This numerical work is performed with commercial CFD-ACE code developed by CFD Research Corporation, and the results are compared wi th the experimental data

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.589-592
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• 2002

A commercial CFD code is applied to analyze the 3-D viscous flow field within vertical multi-stage centrifugal pump including impeller of centrifugal pump with 6 blades and guide vain with 11 blades. The numerical analysis of vertical multi-stage centrifugal pump is performed by changing flow rate from $8\;to\;26\;m^{3}/h$ at the constant 3500rpm. The characteristics such as total pressure coefficient, total head, water horse power, power efficiency are represented according to flow rate changing. In the future, we will need to perform flow calculation of vertical multi-stage centrifugal pump by considering meridional shape of impeller.