• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.961-966
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• 2001

Micro fans of randomly swept-blades were designed to provide C.P.U. in a personal computer with effective cooling in a very quiet mode. The proto--type axial micro-fans machined by a laser sintering machine were tested against manufactured products by comparing the performance and overall sound pressure level with spectral measurements in an environment suggested by ASHRAE and ANSI standards. The predicted OSPLs and directivity patterns of fans by iDesignFan software were in good agreements with measured data. The newly introduced fans of randomly swept-blades were proved to provide a very promising mode of low noise at small loading conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.264-269
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• 2001

Axial fans are widely used in household electrical appliances due to their easy usage and high flow rate for cooling capacity. At the same time, the noise generated by these fans causes one of serious problems. In order to calculate the noise of a fan, we develop the software IFD - Intranet Fans Design. With this software we can design, analysis the performance and predict the noise of fan. The prediction model, which allowed the calculation of acoustic pressure at the blade passing frequency and it's higher harmonic frequencies, has been developed by Lowson's equation. To calculate the unsteady resultant force of the blade, time-marching free-wake method is used. The objective of this study is to calculate the effects of number of blades, rotating velocity, and sweep angle on the noise of fan..

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1013-1021
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• 2005

In this paper, we developed an automatic design optimization system for parametric shape optimization of cooling passages inside axial turbine blades. A parallel three-dimensional thermoelasticity finite element analysis code from an open source system was used to perform automatic thermal and stress analysis of different blade configuration. The developed code was connected to an evolutionary optimizer and built in a design optimization system. Using the optimization system, 279 feasible and optimal solutions were searched. It is provided not only one best solution of the searched solutions, but also information of variation structure and correlation of the 279 solutions in function, variable, and real design spaces. To explore design information, it is proposed a new interpretation approach based on evolutionary clustering and principal component analysis. The interpretation approach might be applicable to the increasing demands in the general area of design optimization.

• The KSFM Journal of Fluid Machinery
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• v.4 no.2 s.11
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• pp.7-14
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• 2001

Design and development of a propeller fan for a cooling tower have been accomplished by both numerical prediction of performance and experimental validation with a wind tunnel. Main interest lies on blade geometry of a fan for optimal design of aerodynamic performance. A commercial program, Fine/Turbo used for the present numerical estimation, gives us engineering information such as flow details near the blades and flow rate of the system. The numerical results are compared with precise experimental output and show good agreement in comparison between the two data. Also new proposed model of a blade shows improved performance relative to present running model in market.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.106-112
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• 2000

Axial fans are widely used in heavy machines due to their ability to produce high flow rate for cooling of engines. At the same time. the noise generated by these fans causes one of the most serious problems. This work is concerned with the low noise technique of discrete frequency noise. The prediction model. which allowed the calculation of acoustic pressure at the blade passing frequency and it's harmonics. has been developed by Farrasat. This theory is founded upon the acoustic radiation of unsteady forces acting on blade. To calculate the unsteady resultant force over the fan blade. Time-Marching Free-Wake Method are used. The fan noise of fan system having unsymmetric engine-room is predicted. In this paper, the discussion is confined to the performance and discrete noise of axial fan and front part of engine room in heavy equipments.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.171-179
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• 2012

Cooling of hot sections, especially the turbine nozzle and rotor blades, has a significant impact on gas turbine performance. In this study, the influence of precooling of the cooling air on the performance of gas turbines and their combined cycle plants was investigated. A state-of-the-art F-class gas turbine was selected, and its design performance was deliberately simulated using detailed component models including turbine blade cooling. Off-design analysis was used to simulate changes in the operating conditions and performance of the gas turbines due to precooling of the cooling air. Thermodynamic and aerodynamic models were used to simulate the performance of the cooled nozzle and rotor blade. In the combined cycle plant, the heat rejected from the cooling air was recovered at the bottoming steam cycle to optimize the overall plant performance. With a 200K decrease of all cooling air stream, an almost 1.78% power upgrade due to increase in main gas flow and a 0.70 percent point efficiency decrease due to the fuel flow increase to maintain design turbine inlet temperature were predicted.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.58-63
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• 2011

The grain size and growth direction of a directionally solidified turbine blade were evaluated by the initial nucleation condition at the start block of directional solidification. The initial nucleation condition was controlled by inserting a Ni foil on the directional solidification plate of the directional solidification furnace. Fine grains with good orientation were obtained in the faster cooling condition at the start block. The nucleus number was compared with the cooling rate of the start block by electron back scattered diffraction (EBSD). DSC (differential scanning calorimeter) analysis was performed to compare the melting point and undercooling for nucleation of the coarse nuclei and fine nuclei of the start block. The faster cooling condition at the start block showed more undercooling for nucleation and smaller size of nuclei which resulted in a fine grain with good orientation in the directional turbine blade.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.411-412
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• 2008

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.1-7
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• 2014

Gas turbines for generation are operated under high temperatures, high pressures and in corrosive environments for long periods of time. This environment causes serious damage to these parts. Therefore, the material, coating, and cooling technology used with a gas turbine are important factors with regard to turbine blade development. One method that can be used to protect a product from harsh conditions is the coating technology. A turbine blade undergoes very aggressive thermal stress and experiences high-temperature fatigue. In order to reduce the surface temperature of the components and protect the blade from high-temperature flames, a thermal barrier coating (TBC) is applied to its substrate. This study confirms the applicability of an inspection system for the turbine blade coating layer using an artificial heat source.

• Laser Solutions
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• v.1 no.1
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• pp.24-29
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• 1998

A new wide laser beam optical system for the laser materials processing has been developed with a polygonal mirror. It consists of polygonal mirror and cooling part that prevents the surface of rotating polygonal mirror from damage by heat. The polygonal minors have been designed and made as 24 and 30 facets in pyramid type. This system provides a uniform linear laser heat source with the surface scanning width from 15 to 50mm according to the scanning height To examine the wide laser beam, He-Ne laser is used. Also, Acryl is used to confirm the laser beam pattern by bum-pattern print To analyze the energy distribution of the wide laser ben empirical values and theoretical values are compared and discussed. To improve the efficiency of the wide laser beam optical system, methods are suggested by the optical theories. For larger area processing like turbine blade, drawing blade, cold roller and guide plate, optimal overlapping locations have been calculated and analyzed by geometric and optical theories.