• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.365-376
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• 2002

An experimental study has been conducted to measure the local film-cooling effectiveness and the heat transfer coefficient for a single row of rectangular-shaped holes. four different cooling hole shapes such ai a straight rectangular hole, a rectangular hole with laterally expanded exit, a circular hole and a two-dimensional slot are tested. A technique using thermochromic liquid crystals determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Both film cooling effectiveness and heat transfer coefficient are measured for various blowing rates and compared with the results of the cylindrical ho1es and the two-dimensional slot. The flow patterns downstream of holes are calculated numerically using a cummercial package. The results show that the rectangular hopes provide better peformance than the cylindrical holes. For the rectangular holes with expanded exit, the penetration is reduced significantly, and the higher and more uniform cooling Peformance is obtained even at relatively high blowing rates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.304-314
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• 2004

An experimental study has been conducted to measure the temperature fields and the local film cooling effectiveness for two and three staggered rows of the rectangular shaped-holes with various blowing rates. The hydraulic diameter of rectangular-shaped hole is 10mm. To compare with the film cooling performance of rectangular-shaped hole, two kinds of circular holes are tested. One has the same hydraulic diameter as the rectangular hole and the other has the same cross sectional area. Also, rectangular holes with expanded exit with same inlet area as rectangular ones are tested. Temperature fields are measured using a thermocouple rake attached on three-axis traversing system. Adiabatic film cooling effectiveness on the surface are obtained based on experimental results of thermochromic liquid crystals. The film cooling effectiveness is measured for various blowing rates and compared with the results for the cylindrical holes. In case of 2 rows, the rectangular holes has better performance than circular holes due to its slot-like geometry. In case of 3 rows, the effecta of hole shape is not clear.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.181-186
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• 2003

An experimental study has been conducted to measure the temperature fields for two and three staggered rows of the rectangular shaped-holes with high turbulence intensity. 10 % turbulence intensity is obtained by installation of two kinds of grids which have different shapes. One grid which is installed at 30d upstream from center of 1st row of holes is composed of vertical cylinders of which diameter is 10 mm and center to center distance is 18 mm. The other installed 15d apart to upstream from center of 1st row of holes which has square pattern is constructed of 3 rum square bars and bar spacing is 25 mm. Temperature fields are measured by using a thermocouple rake which is attached on three-axis traversing system. The results show that the overall values are decreased and the thicker film of coolant is fanned downstream of rows of holes for high mainstream turbulence intensity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.132-136
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• 2004

Experimental study has been conducted to investigate effect of mainstream turbulence intensity on film cooling performance of staggered rows of rectangular holes in combustor. Temperature fields and adiabatic film cooling effectiveness under $10\%$ mainstream turbulence intensity are measured. The results of temperature fields show that overall values are decreased and thicker film of coolant is formed downstream of rows of holes for high mainstream turbulence intensity. The results of film cooling effectiveness show that the values around the holes are smaller than the case of the low mainstream turbulence intensity, however, the difference of film cooing performance is decreasedforthefurtherdownstream.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.739-742
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• 2000

From the experimental study of W-EDM for alloyed steel, the characteristics such as Hand Drum Form and surface roughness have been observed and evaluated for various conditions. In square hole, the increase of If as to made condition the calculate high value of surface roughness. Also compare dimensionless square hole with circle hole' graph. In circle hole, if a value of surface roughness IP 6 in a side of circle it show a 0.4${\mu}{\textrm}{m}$ and in IP 8, 0.6${\mu}{\textrm}{m}$, in IP 10, 0.7${\mu}{\textrm}{m}$, in IP 12. 0.8${\mu}{\textrm}{m}$ higher than before. This figure show the surface roughness is higher than before, because a table move in either X-axis or Y-axis in square hole, on the contrary, in circle there table move in X-axis and Y-axis at the same time. hand drum form getting small when wire tension increase 1000gf to 1500gf, at the same working conditions. the smaller of off time, the mailer of hand drum form in same condition and same wire tension. but if you compare square hole with circle hole' graph hand drum form displayed in maintained term of working condision, on the contrary, in case of square hole variation of hand drum form is more increase than a grow of IP

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.132-139
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• 2003

In this study, it is attempted to obtain the optimum size of holes in 15 square plate models where a hole exists on every quadrant of a plate, and to get eigenvalues by performing free vibration analysis for each model. Moreover, the specimen is produced from optimized square plate and eigenvalue of each plate is measured through the shocking load. And then the result is compared with that of finite element analysis. For free vibration analysis of the square plate, the boundary condition of finite element analysis and experiment is assumed as both ends clamped support. From the results of this study, it is known that more stable structures can be designed by changing the natural frequency which is dependent on the location of holes and further studies are considered to be necessary fur the basic design information.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.436-441
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• 2005

In this study, precision injection molding analysis for BGA connector fabrication was performed. A BGA connector model with rectangular micro-holes were introduced to investigate the effect of mirco patterns on the injection molding process. Dual domain(2.5D) mesh and full 3D mesh for BGA connector model were prepared to perform precision injection molding analysis. To verify the Present analysis, experiments of injection molding were performed based on the results of the analysis. It was shown that the type of mesh has a significant effect on the flow pattern of BGA connector

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.664-667
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• 1997

In this study, it is attempted to obtain the optimized size of holes in 15 square plate models where a hole exists on every quadrant of a plate, and to get eigenvalues and mode shapes by performing free vibration analysis for each model. For free vibration analysis and optimization of' hole sizes, the uniaxial tension is applied for the loading condition. From the results of this study, it is known that more stable structures can be designed by changing the natural frequency depending on the location and the optuiiunl size of holes. and further studies are considered to be necessary for the basic design information.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.779-786
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• 2019

Effects of chamfered perforated plate on pressure loss characteristics were studied with CFD analysis. Both inlet chamfer angle and outlet chamfer angle were considered. Perforated patterns were compared by pressure loss coefficient in certain porosity and Reynolds number. Reynolds number effects were studied for several chamfer angles and plate thickness. As the inlet chamfer angle was increased, the pressure loss coefficient was decreased until the certain angle and reversed to increase. In the outlet chamfered shape cases, the pressure loss coefficient was increased with chamfer angle. Effects of pattern shapes and Reynolds number on pressure loss characteristics were negligible with different chamfer angles and thickness studied in this paper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.10
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• pp.898-906
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• 2005

The present study has been conducted to investigate convective heat/mass transfer in the cooling passage with bleed holes. The rotating square channel has 40.0 mm hydraulic diameter and the bleed holes on the leading surface of the channel. The hole diameter of bleed hole is 4.5mm and its spacing is ( p/d:4.9) about five times of hole diameter. Exit mass flow rate through bleed holes is $10\%$ of the main mass flow rate and relation number is changed form 0.0 to 0.4. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy The cooling performance is influenced by exit mass flow rate through bleed holes and Coriolis force of rotating channel for fixed Reynolds number. The heat transfer on the leading surface is decreased due to Coriolis force. However the total heat transfer is enhanced around holes on the leading surface because of trapping flow by bleeding.