• Journal of KSNVE
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• v.8 no.1
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• pp.122-131
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• 1998

Internal and external acoustic fields of the engine inlet are calculated by using a finite element method. The far fields non reflecting boundary condition is enforced by using a wave envelope element, which is a kind of infinite element. The geometry is assumed an axisymetric duct. Sources of the fan are modeled by the Tyler and Sofrin's theory. Effects of uniformly moving medium are considered. A pulsating sphere and an oscillating piston problem are calculated to verify the external problems, and compared with exact solutions. When the wave envelope element is applied at the far boundary, the calculated finite element solutions show good agreements with the exact solutions. The engine inlet is solved with the combined internal and external grid. The cut-off phenomena on engine inlet duct are observed.

• The KSFM Journal of Fluid Machinery
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• v.11 no.5
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• pp.30-36
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• 2008

Axial fan without static blades requires the duct as a guidance for unskewed inflows. This work examined the geometric effects of a duct guided the in and out flows through an impeller. The present methodologies are computational predictions with parallel work by experimental validation. Several different positions of a rotor in a duct are proposed for plausible models of a rotor inside a duct. The optimum axial position of an impeller in a duct is found at the #4 model where the impeller lies on the inlet edge of a circular duct. The model shows a wider inlet area. The result of computational prediction is in good agreement with experiment measurement.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.50-55
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• 2017

This study is about the distributions of flow in an air conditioning duct used for marine and oil drilling ships. Three-dimensional steady state turbulence was assumed as a governing equation for describing the flow in the air conditioning duct in this study. We compared the flow field with the pressure distribution according to the inlet velocity for two types of air conditioning duct, and stress and safe factors were simulated using ANSYS W/B. The result of fluid analysis showed an increased pressure drop in the duct according to the inlet velocity. Furthermore, secondary flow and complicated flow characteristics occurred at the bellows zone.

• The KSFM Journal of Fluid Machinery
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• v.14 no.4
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• pp.45-51
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• 2011

The kimchi refrigerator is the electronic home appliance which is used for the maturing and a custody of the kimchi. In this paper, performance improvement of fan and duct system for kimchi refrigerator has been studied by using a commercial CFD code. In order to achieve a improved fan performance, three-dimensional computational fluid dynamics and the Design of Experiments method have been applied. Additionally, to know the optimized duct inlet shape with the optimized fan, the overall performances were calculated with various duct inlet shapes. The final fan and duct system for kimchi refrigerator showed improved performance in efficiency and total head compared with the existing model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.4
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• pp.1416-1425
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• 1996

A numerical method has been proposed to predict 3-dimensional flow in a duct system with multiple outlets. For the duct system, it is supposed that the pressure values are given at multiple outlets while the velocity profile is given at a inlet. To maintain the continuity of pressure distribution between main and branch duct, present method allows that the pressure value taken from analysis of branch duct can be converted to the main duct analysis. The result from present method which can handle the pressure boundary condition closely coincided with that from regular method which can handle the velocity boundary condition only. Furthermore the flow distribution from present method showed good agreement with that from the single block method. From the comparison of the present method with the total pressure method used for engineering duct design, 13% of discrepancy in pressure loss was shown between the main duct inlet and the branch duct outlet.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.109-117
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• 2015

Aircraft needs an inlet duct to supply the airflow to engine face. A fighter aircraft that requires low radar observability has to hide the engine face in the fuselage to reduce the Radar Cross Section(RCS). Therefore, the flow path of the inlet duct is changed into S-shape. The performance of the aircraft engine is known to be influenced by the shape and the centerline curvature of the S-Duct. In this study, CFD analysis of the RAE M 2129 S-Duct has been performed to investigate the influence of aspect ratio of inlet geometry. The performance of the S-Duct is evaluated in terms of the distortion coefficient. To simulate the flow under adverse pressure gradient better, $k-{\omega}SST$ turbulence model is employed. The computational results are validated with the ARA experimental data. The secondary flow and the flow separation are observed for all computational cases, while the semi-circular geometry has been found to produce the best results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.641-646
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• 2004

Noise and vibration was encountered in exhaust duct system which is connected with a gas turbine and a heat recovery steam generator(HRSG) of a cogeneration power plants. Especially, these problems occurred when water was added to the fuel injection to reduce NOx contents of the exhaust gas. Through the cavity mode analysis and measurements, It was concluded that these problems occurred due to the acoustic resonance between the duct cavity mode and the excitation force induced by turbulent gas flow during water injection. To reduce the noise and vibration, optimal baffle plate to change the cavity mode was installed inside of duct and noise levels of about 8 dB(A) are reduced in duct system. The effects of baffle plate and guide vane to the HRSG or inlet duct vibration were also evaluated and it was verified that there is no relation to the resonance phenomena. So, vibration of inlet duct was easily reduced by the reinforcement of structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1010-1015
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• 2002

Over the last few decades, noise has played a major role in the development of aircraft engines. The dominant noise is generated by the wake interactions of fan and downstream stator. Engine inlet and exhaust ducts are being fitted with liner materials that aid in damping fan related noise. In this paper, the radiation of duct internal noise from duct open ends with liners is studies via numerical methods. The linearized Euler's equations in generalized curvilinear coordinates are solved by the DRP scheme. The far field sound pressure levels are computed by the Kirchhoff integration method. Through comparison of sound directivity from bell-mouth duct with and without liners, it is shown that radiation from engine inlet is affected by liner effects or a soft wall boundary condition.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.2
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• pp.373-379
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• 2002

This paper was the design of aerosol generator for inhalation toxicology study of lead and evaluation with real time monitoring, and applied several engineering methodology to classical aerosol generator to cope with it's disadvantages. According to the testing conditions, source temperature 50℃ and inlet-duct band heater temperature 150℃, aerosol generation results for sodium chloride and lead acetate were as followings: CPM(Count Per Minute) for Sodium chloride that used for the testing material in aerosol generation and inhalation system was decreased in the 2nd and the 3rd hour's serial trials, but CVs(coefficient of variation) were maintained within 10%. CPMs for 5 and 2.5 gram of lead acetate that used for aerosol generation and inhalation exposure of lead showed similar results because of the sedimentation of lead acetate on piezoelectric crystal with time. For that reason, heating and mixing of nebulizing solution will be needed to generate lead aerosol with stable profile and maximum generation efficiency. Fluctuations of 10 and 5 gram lead acetate were low but 2.5gram was high. However, CVs for 10, 5, and 2.5gram lead acetate were within 10%. Considering the theoretical efficiencies for sodium chloride and lead acetate, 5gram sodium chloride and 2.5gram lead acetate were appropriate choice. Aerosol generation characteristics for two materials with 1 hour interval were different with respect to the fluctuation of CPM and the decrease to 10gram in it's material. For that reason, sodium chloride can not be used to estimate the aerosol generation and it's related parts for lead acetate. According to the testing conditions, source temperature 20, 50, 70℃, and inlet-duct band heater temperature 20, 50, 100, 150, 200℃, aerosol generation results for sodium chloride and lead acetate were as followings: Excluding inlet-duct band temperature 200℃, maximum CPM for sodium chloride was manifested in source temperature 70℃ with each inlet-duct band temperature conditions. We suggest that this condition was the optimum in the design of aerosol generator, inhalation system, and the testing. Maximum CPMs for 10, 5, and 2.5gram sodium chloride were from source temperature 70℃ and inlet-duct band temperature 20℃. Excluding inlet-duct band temperature 50, 200℃, maximum CPMs for lead acetate were indicated in source temperature 50℃ with each inlet-duct band temperature conditions. We suggest that this condition was the optimum in the design of aerosol generator, inhalation system, and the testing for lead inhalation study. Source and inlet-duct band temperatures for 10, 5, 2.5gram lead acetate were 50 and 100℃, 50 and 100℃, 50 and 150℃, respectively. In conclusion, considering above 2 paragraphs of results for aerosol generation, 5gram efficiencies for sodium chloride, lead acetate were higher than 2.5gram's. If inlet-duct band temperature was same, aerosol generation was increased with increase of source temperature. To get maximum aerosol generation will be the conditions that set the appropriate inlet-duel band temperature for each materials and increase the source temperature.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.49-55
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• 2017

In this study, gas turbine engine inlet duct was designed to satisfy uniform flow at aerodynamic interface plane (AIP). Haack-series was selected as nose cone profile and duct outer radius($r_o$) was designed to satisfy to match with area change rate between the nose cone and outer duct wall by the 1-D sizing. The design object of the inlet duct wall profile which has the gradual area change rate was uniform Mach number in the core flow region and minimum boundary later thickness at the both inner nose wall and outer duct wall. The flow characteristics inside the inlet duct was evaluated using CFD. The static pressure distribution at the AIP showed uniform pattern within 0.16%. Based on Mach number profile, the boundary layer thickness was 2% of channel height. Kiel temperature rake location was decided less than 100 mm in front of nose cone where the Mach number is less than 0.1 in order to maximize the temperature probe recovery rate.