• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.9-16
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• 2001

This paper deals with the inverse reconstruction of sectional area in nonuniform ducts by using the acoustical measurement. There have been many theoretical and experimental studies on the duct area reconstruction. In this research, the method using the impulse response function and area reconstruction algorithm was employed because of its mathematical and experimental simplicity. Based on the study results on the drawback of conventional impulse excitation method, a new measurement method is proposed, that uses the random noise source and the discrete inverse Fourier transform. It is found that the reconstruction errors of the present method is smaller than the conventional method. A random error analysis is performed in order to investigate the causes of reconstruction error and to clarify the applicable data range for area reconstruction.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.121-126
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• 2002

Aircraft propulsion systems often use diffusing S-duct to convey air flow from the wing or fuselage intake to the engine compressor, Well designed S-duct should incur minimal total pressure losses and deliver nearly uniform flow with small transverse velocity components at the engine compressor entrance. Reduced total pressure recovery lowers propulsion efficiency and nonuniform flow conditions at the engine face lower engine stall limits. In this study, S-duct which has maximum total pressure recovery and nearly uniform flow profiles at the compressure intake should be found using design optimization methods with 3-dimensional Wavier-Stokes analyses.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.915-917
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• 1992

This paper shows the discharge characteristics in flowing air with variation of tempearature(T) under the needle-needle gap. Flowing air duct of this investigation is circular tube. The flow at the experimental position's section is described as fully developed laminar flow. The important results obtained from this study are as follows. The ratio sparkover voltages to the Reynolds number(Re) increases with decreasing the Re. The velocity profiles can be visualized by this experimental method. The breakdown voltage ($V_{s1}$) for variation of T at 1[m/s] can be expressed by $V_{s1}$ = $K_1$(23.98$\rho$d + 6.98$\sqrt{\rho{d}}$) [kV].

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.10
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• pp.502-509
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• 2002

In the analysis of lightning surges, transmission towers are usually simulated by ATPDraw. The modeling of transmission towers is an essential part of the traveling wave analysis of lightning surges in transmission lines. The tower model is applied to the 154kV transmission tower of which surge performance characteristics are measured Tower surge response is computed using nonuniform, single-phase line models for both transmission tower and ground wire. The overvoltage will effect to the underground transmission line. The underground cable is combined by duct and trefoil type, and the each arrester is placed on the leading-in tube and outgoing tube. This paper analyzed the effect of lightning overvoltage on the underground cable system.