• 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.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.979-989
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• 2004

Numerical simulations have been performed to investigate tip clearance effect on through-flow and performance of a centrifugal compressor which has the same configuration of impeller with six different tip clearances. Secondary flow and loss distribution have been surveyed to understand the flow mechanism due to the tip clearance. Tip leakage flow strongly interacts with mainstream flow and considerably changes the secondary flow and the loss distribution inside the impeller passage. A method has been described to quantitatively estimate the tip clearance effect on the performance drop and the efficiency drop. The tip clearance has caused specific work reduction and additional entropy generation. The former, which is called inviscid loss, is independent of any internal loss and the latter, which is called viscous loss, is dependent on every loss in the flow passage. Two components equally affected the performance drop as the tip clearances were small, while the efficiency drop was influenced by the viscous component alone. The additional entropy generation was modeled with all the kinetic energy of the tip leakage flow. Therefore, the present paper can provide how to quantitatively estimate the tip clearance effect on the performance and efficiency.

• Journal of the Korean Society of Safety
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• v.21 no.4 s.76
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• pp.85-94
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• 2006

In this study, in order to evaluate the effect of two types of connector systems in reinforced retaining wall, the centrifugal tests for the conventional connector and new settlement connector system were performed. In the centrifugal tests, the aluminum plate for the face was used and the aluminum foil was used as a reinforcement. The granite soil was adopted as a fill. As a result, The settlement reinforced retaining wall reached to the failure at 80g-level. In contrast, the conventional reinforced retaining wall was collapsed at 69g-level. It means that the settlement reinforced retaining wall has the stronger stability than the conventional reinforced retaining wall. In addition, it was shown that the settlement connector system is more effective to release the stress concentration occurred at the face of reinforced retaining wall than the conventional connector system.

• International Journal of Fluid Machinery and Systems
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• v.5 no.1
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• pp.38-48
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• 2012

One centrifugal compressor is applied for refrigeration and its working substance is R134a. The operating points obtained by using similar conversion at different rotation speeds are compared with the numerical results. They keep consistent with each other while the rotation speeds are lower, but the error between them will become large with the increasing of the rotation speed. Then the operating points are obtained when the working substance is air by using two similar conversion methods separately. Based on the comparison, it can be obtained that the result of keeping the specific volume ratio of inlet and outlet is more accurate than the result of maintaining Ma number. Then the test result is compared with the similarity result and the numerical result when the working substance is air. It is obtained that the similarity result is more consistent with the test result better than the numerical result and the trend of efficiency and pressure ratio change with the flow rate is consistent with the test result. In the process of similar conversion, the efficiency ${\eta}$ is no useful for similitude design and it has less influence on the conversion result.

• International Journal of Fluid Machinery and Systems
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• v.4 no.2
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• pp.223-228
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• 2011

The performance characteristics of centrifugal pump were measured experimentally when running with tap water and drag-reducing surfactant (Octadecyl dimethyl amine oxide (OB-8)) solutions. Tests have been performed on five cases of surfactant solutions with different concentrations (0ppm (tap water), 200ppm, 500ppm, 900ppm and 1500ppm) and four different rotating speeds of pump (1500rpm, 2000rpm, 2500rpm and 2900rpm). Compared with tap water case, the experimental results show that the total pump heads for surfactant solution cases are higher. And the pump efficiency with surfactant solutions also increases, but the shaft power for surfactant solutions cases decreases compared to t hat for tap water. There exists an optimal temperature for surfactant solutions, which maximizes the pump efficiency.

• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.5-11
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• 2016

The purpose of this study is to design the transonic centrifugal compressor impeller with splitter blades and analyze the flow fields with respect to various splitter blades. Seven impellers with different splitter chord length or pitchwise location were tested by using CFD method. To investigate aerodynamic performance, Mach number distribution and entropy distribution were confirmed. As a result, it is found that the size of transonic region and shock wave location are related to the splitter chord length and pitchwise location. Also the impeller with long chord length of splitter shows higher total pressure ratio but lower efficiency than those of the impeller with short chord length of splitter. In terms of pitchwise location, the impeller with the splitter located in mid-pitch of main blades shows the best performance with respect to pressure ratio and efficiency.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.122-128
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• 2000

Aerodynamic optimization of an automotive air-conditioning blower is a hard task because of the highly complex flow phenomena related to three-dimensional flow separations and the unsteady nature caused by the interaction between primary and secondary air flows throughout the fan. In this paper, an aerodynamic study on a forward-curved centrifugal fan has been carried out Firstly we obtained the fan performance curves versus flow rates showing its unstable nature in the surging operation range. Secondly aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage using a 5-hole pilot probe, at different operating conditions. Surface flow pattern near the cut-off area exhibits similar flow behavior above the best efficiency operating point, although the pressure level increases substantially with the Increase of flow rate. Vorticity in the casing passage flow occurs in all (low rates, downstream from the r-Z plane $\theta$=120 deg., where the position of its core changes with the circumferential location. Although complex, the general flow behavior were common, giving insight in its main aerodynamic features.

• The KSFM Journal of Fluid Machinery
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• v.10 no.4
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• pp.29-38
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• 2007

In this study, flow structure in a two-stage centrifugal compressor for a turbo-chiller with the refrigerant, R134a, was numerically investigated at the design point of the compressor using a commercial code. Flow characteristics in the passages of impeller, diffuser and return channel were analyzed in detail including velocity vector, secondary flow, 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 and the meridional shape of the return channel were performed through the flow analysis, while some numerical schemes and techniques including Multiple Frames of Reference technique, real gas property data and inlet boundary condition changes, which were used in CFD, were compared with their features. The results will be used as reference data for a new design of 3-D impeller shape to improve R134a compressor performance.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3251-3261
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• 1996

Flows were measured in an unshrouded centrifugal impeller. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes between the inlet and outlet of the impeller rotating at 700 rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were estimated from the measured values. Measurements were made for three flow rates corresponding to zero incidence and two others with the greater and the smaller one than zero. From the measured data in these flow rates, the followings were investigated in the impeller passage, the variation of the primary and secondary flows, the leakage flows, the wake's position and its size, the static pressure rise and the loss production mechanism. Furthermore the static pressure and the slip factor were compared with the results of inviscid Quasi-3D calculation.