• Journal of Advanced Marine Engineering and Technology
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• v.32 no.3
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• pp.404-412
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• 2008

As a suitable volute configuration in the range of low specific speed, circular casing is suggested in this study. The internal flows in a centrifugal pump with the circular and spiral casings are measured by PIV and analyzed by CFD. The results show that the head and efficiency of the pump by a circular casing of very small radius are almost same as those by the spiral casing. Even at the best efficiency point, the internal flow of the pump by circular casing is asymmetric, and vortex and strong secondary flow occurs in the impeller passage. The radial velocity becomes higher remarkably only near the region of the discharge throat. The flow in the impeller outlet is strongly controlled by the circular casing because the velocity distribution almost does not affected by the position of the impeller blades.

• Geophysics and Geophysical Exploration
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• v.20 no.4
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• pp.216-225
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• 2017

Recently, steel casing became an interesting issue when applying controlled-source electromagnetic (EM) method to various fields because effects of steel casing on EM responses are not negligible. This study employed an approach that approximates the steel casing as a series of electric dipole sources in order to develop the numerical algorithm for the efficient simulation of EM responses in the presence of steel casing. After verifying the validity of the developed algorithm, we analyze effects of steel casing on EM responses with the synthetic model simulating geothermal reservoir environment. The analysis showed that the effects of steel casing on EM responses are localized near the casing and increase as the transmitter becomes close to the casing. In addition, through the analysis on the EM responses by the injection of clean water, we confirm that the effects of casing are negligible when interpreting the after-injection data acquired using the transmitter located far enough from the casing. Considering the difference in EM responses between before and after injection in inversion, the effects of the casing can be neglected although after-injection data shows considerable difference due to the close distance between the transmitter and casing. To investigate this kind steel casing effect, the precise analysis on EM responses should be preceded. The algorithm introduced in this study will contribute to the reliable calculations of EM responses distorted by the conductive steel casing.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1031-1038
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• 2002

The effects of casing shape on the performance and interaction between the impeller and casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the compressor with circular and single volute casings from inlet to discharge nozzle. In order to predict the flow pattern inside the entire impeller, vaneless diffuer and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and three-dimensional time-averaged Wavier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. To prove the accuracy of numerical results, measurements of static pressure around casing and pressure difference between the inlet and outlet of the compressor are peformed for the circular casing. Comparisons of these results between the experimental and numerical analyses are conducted, and reasonable agreement is obtained.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.463-468
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• 2015

High vibration of a low pressure (LP) turbine casing caused safety problems and life at the facility it was housed in. The main focus of this study was the cause of the high vibration in a low pressure turbine casing with manufacturing defects by frequency response analysis, compared with the results of experiments. Therefore, excited accelerations were obtained from the LP casing fundamental, and frequency responses were analyzed. The measurement and the modal analysis showed that the natural frequency of the LP turbine casing was 61.26 Hz and the excited frequency of the turbine rotor was 60.25 Hz. The manufacturing defect caused a decrease in the casing natural frequency and resulted in the high vibration of the casing because it moved close to the resonant frequency.

• Mycobiology
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• v.36 no.1
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• pp.40-44
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• 2008

Various bacteria were isolated from the casing layer soil of the culture bed of P. ostreatus and their role in fruiting body induction of the edible mushroom, P. ostreatus, was investigated. Analysis of the bacterial community isolated from the casing layer soil revealed that the composition of genera and number of cultivable bacteria were different for each sterilizing treatment. Bordetella was predominant in the bulk soil whereas Flavobacterium was predominant after sterilization of the casing layer soil. Fluorescent Pseudomonas was predominant in the non-sterilized casing layer soil. Total number of the bacterial genera in the casing layer soil was higher than that in the bulk soil. In particular, an increase in the fluorescent Pseudomonas population was observed in the non-sterilized casing layer accompanied by induction of fruiting body and enhanced mushroom production yield. The results suggested that specific bacterial populations in the casing layer play an important role in the formation of primodia and the development of basidiome in P. ostreatus.

• The KSFM Journal of Fluid Machinery
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• v.14 no.5
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• pp.31-38
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• 2011

Optimization using a hybrid multi-objective evolutionary algorithm coupled with response surface approximation has been performed to improve the performance of a transonic axial compressor with circumferential casing grooves. In order to optimize the operating stability and peak adiabatic efficiency of the compressor with circumferential casing grooves, tip clearance, angle distribution at blade tip and the depth of the circumferential casing grooves are selected as design variables. Three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model are discretized by finite volume approximations. The trade-off between two objectives with the interaction of blade and casing treatment is determined and discussed with respect to the representative clusters in the Pareto-optimal solutions compared to the axial compressor without the casing treatment.

• The KSFM Journal of Fluid Machinery
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• v.13 no.2
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• pp.24-29
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• 2010

This paper presents a study on the performance of NASA Rotor 37 with the casing grooves based on three-dimensional numerical analysis. Reynolds-averaged Navier-Stokes equations are solved on a hexahedral grid with the shear stress transport model as a turbulence closure model. The governing equations are discretized by a finite volume method. The validation of the numerical results is performed through experimental data for the total pressure ratio and the adiabatic efficiency. The investigation for an axial compressor with a smooth casing and the casing grooves is carried out to compare the performance parameters, for example, surge margin and efficiency, etc. The surge margin is improved in the case of the casing grooves while remarkable improvement of the efficiency is not produced. The result shows that the casing groove is beneficial to expand the operating range of NASA Rotor 37.

• The KSFM Journal of Fluid Machinery
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• v.16 no.4
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• pp.28-34
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• 2013

Centrifugal pump consists of a axis, a impeller and a spiral casing. The impeller is the most important component in centrifugal pump. But to minimize flow loss in discharge passage including spiral casing, the shape of spiral casing is very important also. So, to investigate the effect of shape of the spiral casing on performance curve of pump, the characteristics of spiral casing were studied through numerical analysis for centrifugal pump used on industry field. From the results the rectangular model was showed more loss than the others because of asymmetric flow field.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.169-174
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• 2016

A cross-flow wind turbine has a high torque coefficient at a low tip speed ratio. Therefore, it is a good candidate for use as a self-starting turbine. Furthermore, it has low noise and excellent stability; therefore, it has attracted attention from the viewpoint of applications as a small wind turbine for an urban district. However, its maximum power coefficient is extremely low (10 %) as compared to that of other small wind turbines. In order to improve the performance and flow condition of the cross-flow rotor, the symmetrical casing with a nozzle and a diffuser are proposed and the experimental research with the symmetrical casing is conducted. The maximum power coefficient is obtained as $C_{pmax}=0.17$ in the case with the casing and $C_{pmax}=0.098$ in the case without the casing. In the present study, the power characteristics of the cross-flow rotor and those of the symmetrical casing with the nozzle and diffuser are investigated. Then, the performance and internal flow patterns of the cross-flow wind turbine with the symmetrical casings are clarified. After that, the effect of the side boards set on the symmetrical casing is discussed on the basis of the analysis results.

• Mycobiology
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• v.38 no.2
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• pp.97-101
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• 2010

Calocybe indica, a tropical edible mushroom, is popular because it has good nutritive value and it can be cultivated commercially. The current investigation was undertaken to determine a suitable substrate and the appropriate thickness of casing materials for the cultivation of C. indica. Optimum mycelial growth was observed in coconut coir substrate. Primordia initiation with the different substrates and casing materials was observed between the 13th and 19th day. The maximum length of stalk was recorded from sugarcane leaf, while diameter of stalk and pileus, and thickness of pileus were found in rice straw substrate. The highest biological and economic yield, and biological efficiency were also obtained in the rice straw substrate. Cow dung and loamy soil, farm-yard manure, loamy soil and sand, and spent oyster mushroom substrates were used as casing materials to evaluate the yield and yield-contributing characteristics of C. indica. The results indicate that the number of effective fruiting bodies, the biological and economic yield, and the biological efficiency were statistically similar all of the casing materials used. The maximum biological efficiency was found in the cow dung and loamy soil casing material. The cow dung and loamy soil (3 cm thick) was the best casing material and the rice straw was the best substrate for the commercial cultivation of C. indica.