• Journal of Microbiology and Biotechnology
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• 제31권6호
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• pp.890-901
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• 2021

The 11α-hydroxylation of canrenone can be catalyzed by Aspergillus ochraceus in bioreactors, where the geometry of the impeller greatly influences the biotransformation. In this study, the effects of the blade number and impeller diameter of a Rushton turbine on the 11α-hydroxylation of canrenone were considered. The results of fermentation experiments using a 50 mm four-blade impeller showed that 3.40% and 11.43% increases in the conversion ratio were achieved by increasing the blade number and impeller diameter, respectively. However, with an impeller diameter of 60 mm, the conversion ratio with a six-blade impeller was 14.42% lower than that with a four-blade impeller. Data from cold model experiments with a large-diameter six-blade impeller indicated that the serious leakage of inclusions and a 22.08% enzyme activity retention led to a low conversion ratio. Numerical simulations suggested that there was good gas distribution and high fluid flow velocity when the fluid was stirred by large-diameter impellers, resulting in a high dissolved oxygen content and good bulk circulation, which positively affected hyphal growth and metabolism. However, a large-diameter six-blade impeller created overly high shear compared to a large-diameter four-blade impeller, thereby decreasing the conversion ratio. The average shear rates of the former and latter cases were 43.25 s^-1 and 35.31 s^-1, respectively. We therefore concluded that appropriate shear should be applied in the 11α-hydroxylation of canrenone. Overall, this study provides basic data for the scaled-up production of 11α-hydroxycanrenone.

• 한국산업융합학회 논문집
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• 제9권4호
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• pp.247-253
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• 2006

Power consumption for double-stage paddle impeller in spherical and cylindrical agitated vessel was measured over a wide range of Reynolds number from laminar to turbulent flow regions. The power correlation was obtained which was applied to both spherical and cylindrical vessel, when the apparent diameter of the spherical vessel was equal to the diameter of the cylindrical vessel which had a height equal to its diameter and had the same volume as the spherical vessel. The power consumption for the double-stage impeller was dependent upon the distance of among the impeller in the agitated vessels, as follows: $$f/2={\frac{C_L}{Re_G}}+{\frac{Ct}{2}}({\frac{C_tr}{Re_g}}+Re_g)^{-m}$$

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.59-66
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• 1999

In this study the effects of nozzle diameter on the performance characteristics for the tangential impeller-type water meter are studied experimentally. The nozzle is cut along the tangential direction of the inner case in the water meter. The nozzle shape is round and the number of nozzles used for the experimental study are 8. The performance characteristics are discussed for various nozzle diameters such as 3.1, 3.3, 3.5, 4.0, 4.5 and 5.0 mm. Among the tangential impeller-type water meters, the water meter with the nozzle diameter of 5.0 mm shows the least pressure loss and the instrumental error compared to the Korean Standards.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.391-396
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• 2003

A cross-flow fan relatively produces higher dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. The performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, and 15% by the heat exchanger. At the low flow rate, there exist a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. The purpose of this study is to investigate the reciprocal relation among each parameter Experiments are conducted to study the effects of a rearguider and a diameter ratio of impeller on the performance analysis of a cross-flow fan. Comparing with the rearguider of radial type, the Archimedes type shows excellent results for various diameter ratios.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1322-1325
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• 2009

The impeller and vane diffuser for the mixed flow pump(NS550) was designed by using meridional selection program and inverse design method. We decided the meridional shape of the impeller from the meridional design parameter, such as the specific speed and maximum diameter at the impeller exit. The meridional shape of vane diffuser was set from the impeller shape, distribution of cross sectional area and maximum diffuser diameter. The angle of impeller blade and diffuser vane was designed by using inverse design method. The predicted overall performance by using commercial CFD code(ANSYS CFX-11) shown good agreement with design goals.

• 소음진동
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• 제10권3호
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• pp.523-530
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• 2000

In this paper we present an efficient method for finite element vibration analysis of a structure with cyclic symmetry and applied it to calculating the natural vibration characteristics for a blower impeller. Blower impeller having a cyclically symmetric structure is composed of circumferentially repeated substructures., The whole-structure is partitioned into substructures and then finite element vibration analysis is performed for a substructure using transformed equations for each number of nodal diameter which are derived from discrete Fourier transform in consideration of the cyclic symmetry. natural vibration characteristics for three kinds of models which are blower impeller without support ring with small support ring and with large support ring are numerically analyzed and compared. Accuracy and efficiency of the present method are verified by comparison of results of the analysis with substructure and with whole-structure. Also the results of the analysis by cyclic symmetry module(SOL 115) of MSC/NASTRAN are presented and compared.

• 대한조선학회논문집
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• 제41권5호
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• pp.21-27
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• 2004

A waterjet propulsion system has many advantages compared with a conventional screw propeller especially for amphibious military vehicles because of a good maneuverability at low speed, good operating ability at shallow water, high thrust at low speed to aid maneuverability and exit from water, etc. Especially, compact design is important for the tracked-vehicle because of buoyancy in water and available space inside the tracked vehicle. The experiment is parametrically performed for various impeller diameters for more compact design. The experimental results are analyzed according to the ITTC 1996 standard analysis method as well as the conventional propulsive factor analysis method. The full-scale effective and delivered power of the tracked-vehicle are evaluated according to the variation of impeller diameter. This paper emphasized the effect of impeller diameter on the performance of waterjet system.

• 한국압력기기공학회 논문집
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• 제8권3호
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• pp.23-27
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• 2012

A seawater pumps in the nuclear power plant is responsible for providing cooling water to other components all the time. Because of the depreciation, the seawater pump with current impeller consumes too much power for maintaining the total head. Therefore the objective of this study is to reduce power with maintaining certain the total head by cutting the current impeller. By using a commercial CFD code, FLUENT, the overall performance of seawater pump with current and modified impeller was simulated. Also Affinity law was applied at pumps with various impeller diameter and evaluated the validity of the affinity law. The numerical results show that the pump efficiency is quite irrelevant to the diameters of the impellers and the pump efficiency becomes worse over the designed flow rate. And affinity law result and numerical one show good agreements at small change of impeller diameter. One of the impeller diameters was decided to modify and was applied to the nuclear power plant with the numerical study above.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.61-66
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• 2012

Nowadays, precise prediction of the pump performance becomes more important than ever before in high-value industries such as power plants and large ships. The power consumed in such pumps of large head and capacity definitely affects the efficiency of the entire system. In this study, we report the theoretical and CFD results used in prediction of the performance change caused by the reduction of impeller diameter. We have found that the theoretical calculation is somehow useful at least in estimating the very beginning condition for the CFD main calculation.

• 한국기계가공학회지
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• 제18권2호
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• pp.52-57
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• 2019

To develop a stirring device that can automatically measure the viscosity of a fluid, the impeller type of the device must be recognized without making contact. In this study, we propose a method to discriminate the type of impellers using the changes in the magnetic field. Permanent magnets are inserted into a hollow hole of the impellers, and the change of the magnetic field is measured by a hall sensor. All experimental results are compared with the FEM analysis results. The results show that with the increase in diameter and length of the magnet inserted into the impeller, the magnitude of the magnetic flux density increases. The magnetic field is more sensitive to the change in the magnet diameter than to the change in magnet length. In order to reduce the machining costs, however, it is advantageous to change the magnet length instead of the magnet diameter.