• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3639-3648
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• 1996

The effect of 15% pinched diffuser in a centrifugal air compressor with a cascade airfoil diffuser on the aerodynamic performance is investigated using a numerical approach. The commercial CFD code for three-dimensional, turbulent, compressible flow fields is executed for various mass flow rates at a design speed which can be obtained as long as the calculation succeeds. The pinched diffuser is found to help improve the instability of flow within vaneless diffuser space, especially the reverse flow near shroud, and to change both stall/surge line and choking line to increase the surge margin. It is also found to generate more favorable increase of static pressure in diffuser region, and to increase the resulting pressure ratio and efficiency.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.128-137
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• 1998

In this numerical experiment, the preconditioned compressible Navier-Stokes equation is tested to analyze the laminar spray combustion. Sprayed flow field is formulated by Eulerian-Lagrangian system for the gas and liquid phases each. DSF(Deterministic Separated Flow) model was adopted for the sprays with the vortex model to describe transients of individual droplet heating. Simplified single global reaction model approximates methanol-air reaction with and without disk flame holder. The equation system is discretized by finite difference technique and time integrated by LU-SGS. Due to greatly simplified chemical reaction mechanism and the lack of experimental evidences, most of the efforts were devoted to show the applicability and robustness of preconditioned compressible flow calculation algorithm. Computation results in qualitatively reasonable combusting flow field, hence it is believed that further refinement are required to produce quantitatively accurate solutions.

• Journal of environmental and Sanitary engineering
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• v.23 no.3
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• pp.47-57
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• 2008

This study was predicted the diffusion of the conservative contaminant using a two-dimensional hydraulic model. The research area is upper basin of Jakwang river where the possibility where the pollutant of vast quantity will flow is high. Using SMS model, we calculated two-dimensional stream flow. And using this result, predicted the conduct of the conservative contaminant by pollutant transfer diffusion calculation. And also we predicted flow and contaminant diffusion in the near estuary by constructed guide bank. As a result of study, pollutant effect scope of the conservative contaminant was predicted with the fact that will broaden because of interception by guide bank. As discharge was increased from the Jakwang river, The diffusion of the pollutant is accelerated, also the effect scope increases.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.509-511
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• 2001

In the competitive electricity market, various pricing methods are developed and practiced in many countries. Among these pricing methods, marginal loss factor(MLF) can be applied to reflect the marginal cost of network losses. For the calculation of MLF, power flow method has been used. However, it shows some shortcomings such as necessity of regional reference node, and absence of an ability to consider network constraints. The former defect might affect adversely to the equity of market participants and the latter might generate an inappropriate price signal. To overcome these defects, the utilization of optimal power flow(OPF) is suggested in this paper. 30-bus system is used for the case study to compare the MLF by the power flow and the OPF method for 24-hour dispatching and pricing.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.445-451
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• 2004

Four design candidates for a 1.4MW class partial admission turbine have been chosen from a Preliminary design process. Their performance were estimated through the 3-D numerical analyses using a frozen rotor method. In order to select the optimum design, each flow analysis result was compared with others. Flow characteristics in the passages and some types of losses induced by shocks and wakes were found from calculation results. Based on these calculations, a new rotor blade was redesigned and compared with previous one through flow analysis.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.660-664
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• 2004

The flow fields of a lubrication oil pump has been simulated by using CFD in order to improve performance of the pump. The grid for the one flow passage is applied for estimating pump performance. The calculation result shows that there are unfavorable flow characteristics of flow recirculation in the casing part by the guide vane. Thus, the guide vane is modified to reduce the recirculation region. Performance test shows that the modified model pump efficiency is increased by $6\%$ at the rated point compared to that of the original model.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1358-1365
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• 2008

By Computational Fluid Dynamics simulation, general information about an internal gas flow can be achieved. This will be very useful to improve flow inside the pipes and snubber system. Relating with hydrogen compressing system, which plays an important role in hydrogen energy utilization, this method should be a powerful tool to observe the flow quickly and clearly. Flow pressure characteristic analysis of hydrogen gas flowing through the snubber of a reciprocating compressor is presented in this paper. The CFD calculation of pressure pulsation and pressure loss are very close to the experiment. Therefore, consequently development of the better hydrogen compressing system will be observed with better understanding by CFD.

• 연구논문집
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• s.28
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• pp.39-47
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• 1998

Industrial electrostatic precipitation is a very complex process, which involves multiple-way interaction between the electric field, the fluid flow, and the particulate motion. This paper describes a strongly coupled calculation procedure for the rigorous computation of particle dynamics during electrostatic precipitation. The turbulent gas flow and the particle motion under electrostatic forces are calculated by using the commercial computational fluid dynamics (CFD) package FLUENT linked to a finite-volume solver for the electric field and ion charge. Particle charge is determined from both local electrical conditions and the cell residence time which the particle has experienced through its path. Particle charge density and the particle velocity are averaged in a control volume to use Lagrangian information of the particle motion in calculating the gas and electric fields. The turbulent particulate transport and the effects of particulate space charge on the electrical current flow are investigated. The calculated results for poly-dispersed particles are compared with those for mono-dispersed particles, and significant differences are demonstrated.

• Ocean and Polar Research
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• v.21 no.2
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• pp.87-97
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• 1999

To estimate absolute transports by advection in the southwestern East Sea (Japan Sea), an inverse method was applied to CTD data obtained in July 1993. The relative velocities are calculated using the thermal wind equation. The inverse model was formulated to obtain a reference velocity based on the mass conservation in each of four vertical layers within a region enclosed by hydrographic sections and the coastal boundary. The flow patterns in the surface layer are clockwise and anti-clockwise in the regions south and northwest of Ulleung Island, respectively, and a strong northward flow appears in between them. In the second layer, the flow fields are generally weak. The inverse calculation yields the southward flow along the coast, and this suggests that the subsurface low salinity water in the Ulleung Basin is supplied by the southward transport along the east coast of Korea.

• Journal of Korea Foundry Society
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• v.12 no.1
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• pp.40-50
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• 1992

A computer simulation of mold filling has been performed in order to analyze the fluid flow pattern in a mold cavity since casting defects such as cold shut formation, entrapment of air or gas, and inclusions are closely related to the fluid flow phenomena. The flow of molten metal entering the mold cavity with free surface has been modeled by SMAC(Simplified Marker and Cell) method. Two dimensional analysis was carried out on plate shape castings with two types of gate system. The calculation results were compared with those of water modeling experiments and showed relatively good agreement.