• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.519-522
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• 2006

Experimental and computational studies on an turbopump inducer with and without a bearing strut were performed to evaluate the effects of a strut on the performance of an inducer. Global performance data such as head rise and efficiency, and detailed flow characteristics such as surface static pressures were measured and compared with computational results. Generally a good agreement is observed between experimental and computational results, but some discrepancies are observed due to complex flow features such as backflows at the inlet and strut/inducer interactions. For the flow rates where the backflow region is large, installing a strut enhanced the hydraulic performance of the inducer by diminishing the size of the backflows. The results also show that the strut has negligible effect on the suction performance of the inducer.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.745-750
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• 2000

A numerical code which can simulate unsteady, incompressible and 3-dimensional flows in an engine cylinder has been developed. The governing equations based on the cylindrical coordinate are discretized by the finite volume method with staggered variable arrangements. A geometric conservation rule is also incorporated into the simulation code in order to deal with a moving boundary problem. For the unsteady simulation, a fractional step method is adopted. The law of wall is applied to the wall boundaries and standard $k-\;{\varepsilon}$ model is used to describe the in-cylinder turbulent flow. The model cylinder has one eccentric port, flat piston and flat cylinder-head. The comparisons with experimental data show fairly well qualitative agreement.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2233-2238
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• 2003

It is well known that organized vortex rotations swirl and tumble greatly affect the mixing, the combustion and heat transfer processes in engine cylinder. We have developed 3 dimensional numerical simulation codes whose predictions make good agreement with the experimental data. Large eddy simulation based on Smagorinsky subgrid scale model was adopted to describe the turbulence of in-cylinder flows. The tumble motions generated by different inclination angles between valve-port and cylinder head have been calculated. The results show that the angles between direction of induced flow and cylinder walls which the flow collides with play a great role in the formation and generation of tumble motions. Therefore, it is inferred that seat angle and inclination angle are important factors of engine design. In addition, the numerical results of different engine speed -1000 rpm and 3000 rpm are very similar in the flow structure.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.37-42
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• 2010

This paper deals with the sealing mechanism of the gasket component and the effects of design parameters for the exhaust manifold. The finite element model includes hot-end exhaust system and a simplified gasket model supplied by ABAQUS software. The mechanical behaviors of bead and body of a gasket are measured after several times of cyclic loads by gasket supplier. From the finite element analysis due to the cyclic thermal loads, the flange of exhaust manifold shows thermal expansion and contraction in longitudinal direction as well as convex and concave deformations with respect to the engine cylinder head. And, the contact pressures of the gasket beads suddenly changes by normal deformation of inlet flanges. Therefore, the magnitudes of contact pressures could be used to determine the sealing characteristics of the exhaust gas in the exhaust system. The distributions of contact pressures in gasket bead lines shows a good agreement with the engine test results.

• Journal of KSNVE
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• v.8 no.1
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• pp.187-194
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• 1998

In order to predict the train noise propagation from a level railroad, this paper presents the model of train noise source and the prediction model based on the results by using the sound intensity method. The prediction model gives the effects of geometric attenuation, ground attenuation, and barrier attenuation of noise. There are several principal assumption in developing model: (a) the train noise is primarily rolling noise; (b) the rail head and wheels are in good condition; (c) the height of source is 10cm above track; (d) the directivity pattern of train noise sources is a dipole source. Calculated results based on this model are compared with available field data and good agreement has been obtained.

• Journal of the Korean Society for Railway
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• v.7 no.2
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• pp.149-154
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• 2004

Pile Bridge Abutments constructed on a soft base are affected by a lateral flow. Laterl flow pressure acting on Pile is very difficult to calculate because of, interation of ground and Pile. So, it is different to estimate displacement of Pile Bridge Abutments. This paper studied about possibility of the displacement estimation of Pile Bridge Abutments by using the equivalent sheet pile wall theory that was Randolph proposed in 1981. Analysis program through using the SAGE CRISP that is FEM program. Analysis data used Centrifuge test results of Springman(1991), Bransby(1997) and Ellis(1997)'s paper. In conclusion, maxium displacement that is carried out by centrifuge test and numerical analysis has occured at the head of pile, as well as Maximum displacement of pile is closely similar. But the moment acting on pile of numerical analysis is under estimated compare to the centrifuge test. Through the comparative study, it is found that displacement estimation by equivalent sheet pile wall is in relatively good agreement with the results of centrifuge test.

• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.16-20
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• 2006

The present study focuses on the flow analysis of a turbo pump inducer by performing both numerical and experimental methods. The head rise, efficiency and detailed flow fields such as outlet flow angles, pressure and velocity vectors are measured and compared with the computational data. Generally a good agreement is obtained between numerical and experimental results. However, some discrepancies are observed due to complex flow structures inside the inducer. Future calculations with an advanced turbulence model and a dense computational grid needs to be performed to obtain accurate numerical solution for the detailed flow fields.

• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.47-52
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• 2014

An inducer is forward-attached to an impeller to improve the suction performance. This paper described the experimental and numerical investigations on the concept of NPSH similarity about the inducer scale. As Reynolds number decreased for the same scale inducer, the hydraulic performance is slightly reduced because of the viscosity. The suction performance similarity is in good agreement. For different scale inducers, the NPSH similarity did not follow the conventional rule which is proportional to the square of the inducer diameter. A cavity of two times scale inducer grows faster under cavitation inception, and the head is more drop as the fluid passes blades. Because of the simplified cavitation model and vapor pressure, the NPSH similarity dose not have an accuracy. This study suggested an empirical formula for the NPSH similarity.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.15-18
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• 1990

In this paper, perpendicular magnetic recording system which consists of a single pole head and a double, layer medium is analyzed by using 2D-finite element simulation and Preisach model for describing hysteresis characteristics. For confirming this method, we compare the calculated magnetic field intensity which is above the isolated transition of magnetization and scale up experimental data which have already published. The results show a good agreement and we can conclude that this method is very useful to analyze perpendicular magnetic recording system.

• Journal of Microbiology
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• v.34 no.1
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• pp.1-6
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• 1996

The nucleic acid of Synechococcus sp. cyanophage was identified as double-stranded DNA by the result of digestion with enzymes such as exonucleases, DNase, and S1 nuclease, and by acridine orange staining. The cyanophage DNA was cleaved with several restriciton ehdonucleases such as ApaI, BamHI, Bg/II, HaeIII, Eco RI, HindIII, PstI, AND aPAI gave the clearest sets of bands on agarose gels and the fragment numbers for each were 12, 20, 29, 20, and 7, respectively. The sums of the size from Bam HI and PstI digestions were estimated approximately 227$\pm$4 kb, which are in agreement with the result of the pulsed field gel electrphoresis. This virus is thought to have the largest genosome among those of known cyanophages, which corresponds to the largest haed ot 90 nm when compared with the head sizes of cyanophages discovered since 1963.