• International Journal of Fluid Machinery and Systems
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• v.3 no.3
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• pp.245-252
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• 2010

It's known that pump head of centrifugal impeller with lager blade outlet angle is kept higher in air-water two phase flow condition, though the efficiency in water single phase flow condition is inferior. In the present study, a centrifugal impeller with variable blade outlet angles, that has higher efficiencies in both water single phase flow and air-water two phase flow conditions, is proposed. And the performances of the centrifugal impeller with variable blade outlet angles were experimentally investigated in both flow conditions of single and two-phase. In addition, effects of installing diffuser vanes on the performances of centrifugal pump with movable bladed impeller were also examined. The results are as follows: (1) The movable bladed impeller that proposed in this study is effective for higher efficiency in both water single phase and air-water two phase flow conditions. (2) When diffuser vanes are installed, the efficiency of movable bladed impeller decreases particularly at large water flow rate in water single-phase flow condition; (3) The performances of movable bladed impeller are improved by installing of diffuser vanes in air-water two-phase flow condition at relatively small water rate. The improvement by installing of diffuser vanes however disappears at large water flow rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.819-825
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• 2006

In a SOFC/GT (solid oxide fuel cell/gas turbine) hybrid power generation system, the recuperator is an indispensible component to enhance system performance. Since the expansion ratio to the recuperator core is very large, generally, the effective header design to distribute the flow uniformly before entering the core is crucial to guarantee the required performance. In the present study, we focus on the design of a diffuser type recuperator header with a 90 degree turn inlet port. To reduce the flow separation and recirculation flows, multiple horizontal vanes are used. The number of horizontal vanes is varied from 0 to 24. The air flow velocity is measured at 40 points just behind the core outlet by using a hot wire anemometer. Then, the flow non-uniformity is evaluated from the measured flow velocity. The experimental results showed that inlet air velocity did not effect on relative flow non-uniformity. According to increasing the number of horizontal vanes, flow non-uniformity reduced about $40{\sim}50%$ than without using horizontal vanes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.877-880
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• 2017

Impeller blades in the centrifugal compressor are subjected to static loads due to the high-speed rotation and steady aerodynamic forces. At the same time, aerodynamic excitations by the interaction between the impeller and the diffuser vanes(DV) periodically excite the impeller blades in resonant conditions, which may lead to high cycle fatigue (HCF) and eventually result in failure of the blades. In order to predict the structural response accurately, the aerodynamic excitation and the major resonant conditions were predicted by performing the unsteady flow analysis and modal analysis using ANSYS. Next, a unidirectional forced vibration analysis was performed by using fluid-structure interaction (FSI) method, and the safety of HCF was evaluated based on the results.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.469-475
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• 2003

The performance of a centrifugal compressor composed of an impeller, tandem diffuser rows and axial guide vanes has been predicted numerically and compared with available experimental results on its design rotational speed. The pitchwise-averaged mixing plane method was employed for the boundaries between rotor and stator to obtain steady state solutions. The overall characteristics showed differently according to the relative positions of tandem diffuser rows while the characteristics of impeller showed almost identical. The numerical results agree with the measured data in respect of their tendency. It turned out that 0% of relative positions is the worst case in terms of static pressure recovery and efficiency. According to the experimental results, some pressure fluctuations and malfunction of the compressor were observed for 75% case. However, this numerical calculation using mixing plane method did not capture any of those phenomena. Thus, unsteady flow calculation should be performed to investigate the stability of the compressor caused by different diffuser configuration.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.24-35
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• 2018

Impeller blades in the centrifugal compressor are subjected to periodic aerodynamic excitations by interactions between the impeller and the diffuser vanes (DV) in resonant conditions. This may cause high cycle fatigue (HCF) and eventually result in failure of the blades. In order to predict the structural response accurately, the aerodynamic excitation and the major resonant conditions were predicted using unsteady computational fluid dynamics (CFD) and structural analysis. Then, a forced vibration analysis was performed by going through one-way fluid-structure interaction (FSI). A numerical analysis procedure was established to evaluate the structural safety with respect to HCF. The numerical analysis procedure proposed in this paper is expected to contribute toward preventing HCF problems in the initial design stage of an impeller.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.55-60
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• 1999

A centrifugal compressor was tested with three different diffusers with plate vanes. The vane inlet angle was varied from 15 to 30 dog. The higher static pressure rises are obtained with lower vane stagger angle. In the stable region the static pressure field in vaneless space is very sensitive to flow rate. The impeller has a stabilizing effect over the whole stable operating range. The diffuser has a stabilizing effect at high flow rate but is destabilizing at low flow rate.

• The KSFM Journal of Fluid Machinery
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• v.7 no.2 s.23
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• pp.27-34
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• 2004

The performance of a centrifugal compressor composed of an impeller, tandem diffuser rows and axial guide vanes has been predicted numerically and compared with available experimental results on its design rotational speed. The pitchwise-averaged mixing plane method was employed for the boundaries between rotor and stator to obtain steady state solutions. The overall characteristics showed difference according to the relative positions of tandem diffuser rows while the characteristics of impeller showed almost identical result. The numerical results agree with the measured data in respect of their tendency. It turned out that $0\%$ of relative positions is the worst case in terms of static pressure recovery and efficiency. According to the experimental results, some pressure fluctuations and malfunction of the compressor were observed for $75\%$ case. However, this numerical calculation using mixing plane method did not capture any of those phenomena. Thus, unsteady flow calculation should be performed to investigate the stability of the compressor caused by different diffuser configuration.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.177-184
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• 2001

For two kinds of the multi-stage centrifugal pump with diffuser vanes and return channel vanes the meanline performance prediction is applied to get information of hydraulic performance at each internal flow station, because only flange-to-flange test curves are available. As a first step of redesign fur higher efficiency, the impeller geometry is numerically investigated in the present study. Quasi-3D inviscid loading distributions are obtained, for the two impellers, using the state-of-the-art method of impeller 3D design, which provides a guide to optimal redesign. Full 3D turbulent flow fields are thereafter analyzed, using the specialized CFD code, to confirm the redesign results. The inherent limitation of the traditional graphic method of impeller design, which most of domestic pump manufacturers are now employing, is found.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.672-677
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• 2001

This study has been conducted to design the high efficiency centrifugal compressor for a HFC-134a. The 2-stage centrifugal compressor consists of inlet guide vanes, two impellers with splitters, a deswirler, a vaneless diffuser and a volute casing. We have designed the high efficiency centrifugal compressor by applying the repeated design procedure including a meanline design, a 3D geometry generation of 1st and 2nd impellers etc. Also, a fluid dynamic calculation of impellers and deswirler have been conducting using a commercial code STAR-CD.

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.103-103
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• 2005