• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.168-174
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• 1983

The study is concerned with an analysis on the hydrofilm extrusion through conical dies. The upper bound method is adopted for the analysis of metal deformation in connection with hydrodynamic lubrication theory for the lubricant in order to determine the extrusion pressure for some variables such as reduction of area, die cone angle. In the upper bound method, a kinematically admissible velocity field is found by assuming proper streamlines and applying the flow function concept to the region of plastic deformation. The effect of work hardening is incorporated approximately by calculating the strains at the exit of the die. The experiments are carried out with the commercially pure aluminium for some chosen variables at room temperature. It is shown that the theoretical predictions are in good agreement with the experimental observations.

• Journal of ILASS-Korea
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• v.11 no.2
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• pp.113-120
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• 2006

The effect of internal liquid flow on spray plume characteristics was performed experimentally in subsonic cross flows. The injector internal flow was classified as three modes such as a normal, cavitation, and hydraulic flip. The objectives of the research are to investigate the effect of internal liquid flow on the spray plume characteristics and compare the trajectory of spray plume with previous works. The results suggest that the trajectory and width of spray plume can be correlated as a function of liquid/air momentum flux ratio(q), injector diameter and normalized distance from the injector exit(x/d). It's also found that the injector internal turbulence influences the spray plume characteristics significantly.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.97-103
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• 2008

Unsteady three-dimensional flowfields generated by transverse fuel injection into a supersonic mainstream are simulated with a DES turbulence model. Comparisons are made with experimental results in term of the temporal eddy position and eddy formation frequency. The vorticity field around the jet exit is also analyzed to understand the formation mechanism of the jet vortical structures. Results indicate that the DES model correctly predicts the convection characteristics of the large scale eddies. However, it is also observed that the numerical results slightly overpredict the eddy formation frequency. The jet vortical structures are developed from the competing vortices in the recirculation region of upstream boundary.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.267-271
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• 2000

The local heat transfer rate of an axisymmetric submerged air jet impinging on normal to a heated flat plate was investigated experimentally with varying solidity of mesh screen. The mean velocity and turbulent Intensity profiles of streamwise velocity component were measured using a hot-wire anemometry. The temperature distribution on the heated flat surface was measured with thermocouples. The screen installed in front of the nozzle exit(behind of 35mm) modify the jet flow structure and local heat transfer characteristics. For higher solidity screen, turbulence intensity at core lesion is high and increases the local heat transfer rate at nozzle-to-plate spacings(L/D<6). For larger nozzle-to-plate spacings(L/D>6), however, the turbulent Intensities of all screens tested in this study approach to an asymptotic curve, but the small mean velocity at the core region reduces the local heat transfer rate for high solidity screens.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.422-427
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• 2000

The design of low-solidity vaned diffusers and the effect on the performance of a turbocharger compressor is discussed. The effect of vane number and turning angle was investigated while maintaining a basic design with a leading edge angle of $70^{\circ}$, leading and trailing edge radius ratios of 1.1 and 1.3. All results are compared with those obtained with the standard vaneless diffuser configuration and it was shown that all designs increased and shifted the pressure ratio to reduced flowrates. Despite the low-solidity configuration none of the vane designs provided a broad operating range, and the vane leading edge angle was not main factor that system went into the surge condition. The diffuser of higher trailing edge angle improved the flow range for the compressor to operate at lower flow region.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.4
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• pp.38-43
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• 2010

By generating 2-directional vibration in a xy plane of workpiece table, a newly developed micro drilling using 2-directional vibration was carried out. The vibration was produced by applying sinusoidal voltages to the orthogonally arranged piezoelectric materials built in the workpiece excitation table. Through the micro-drilling experiments using poly-carbonate and brass material, it was found that micro drilling using 2-directional vibration in a workpiece table could be an efficient method to enhance the form accuracy of machined workpiece by suppressing burr formation at both entry and exit region. A higher form accuracy could be obtained by increasing stiffness of feeding mechanism, decrease of geometric tolerance of combining jig, and development of high performance excitation table which generates amplified vibration at higher frequency.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.97-103
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• 2008

Unsteady three-dimensional flowfields generated by transverse fuel injection into a supersonic mainstream are simulated with a DES turbulence model. Comparisons are made with experimental results in term of the temporal eddy position and eddy formation frequency. The vorticity field around the jet exit is also analyzed to understand the formation mechanism of the jet vortical structures. Results indicate that the DES model correctly predicts the convection characteristics of the large scale eddies. However, it is also observed that the numerical results slightly overpredict the eddy formation frequency. The jet vortical structures are developed from the competing vortices in the recirculation region of upstream boundary.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.34-35
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• 2004

Three dimensional density distributions of impinging and eccentric flames have been investigated by digital speckle tomography. The flames have been ignited by a mixture of butane and air from a circular nozzle and impinged against a plate located at the upper side of the burner exit. For comparison with experimental data, computer synthesized phantoms of impinging and eccentric flames have been reconstructed by a developed three-dimensional multiplicative algebraic reconstruction technique (MART). The advanced reconstruction in the stagnation flow region involved the sharp change of the flow direction and pressure gradient has been developed using a cross-correlation method and new scanning technique for the speckle displacement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.823-826
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• 2000

Burr formed in drilling are classified into three types. no burr, burrs with cap, teared burr. To control burr size in drilling. the second type burrs with cap are to be formed because it is small and uniform. It is necessary to understand the mechanism of cap formation to derive the burr formation into second type burr with cap. In several materials, second type burrs are formed in drilling by changing cutting conditions. It is observed that cap is formed as a result of the plastic deformation along the outside of exit hole. According to the tension behavior of the material in concentrated region between hole and drill outside edge, the geometry of burr with cap is determined.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.233-236
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• 2002

The high-pressurized spray nozzle is used f3r special washing and cutting with strong impact force. The performance of this nozzle, which focused on spray penetration and radial dispersion, was mainly investigated to maximize the momentum and minimize the flow loss. Hence, our experimental research was conducted by changing the aspect ratio ranging from 0 to 3 with nozzle outlet of 1.1. The spray trajectory far high-pressurized water was experimentally investigated using PDPA diagnostics, which was available at spray downstream region. As the spray at upstream near the nozzle exit did not show the improved disintegration. The results showed empirical correlation with regard to non-dimensional axial velocity distribution, spray penetration, and radial spreading rate with photographic visualization.