• 한국소음진동공학회논문집
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• 제15권2호
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• pp.129-134
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• 2005

This paper describes the influence of geometric parameters on the noise generation from a centrifugal compressor. From the analysis of noise measurements, it is observed that Blade Passing Frequency noise related to the rotating impeller is more important, and it is focused on the comparison of this discrete frequency noise according to the shape change. Navier-Stokes solver is used to simulate the flow-field of the impeller and the vaned diffuser, and time-dependent pressure data are calculated and Fourier-transformed to perform the near-field noise prediction. The effects of various geometry design variables such as the gap between the impeller and the diffuser, impeller shape variations on the near-field noise distribution are investigated.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.71-74
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• 2005

The present study describes the prediction of the flow induced noise level of a high-speed rotating hexagonal disk and proposes the way how to reduce it. Since a hexagonal disk, which is used in the laser printer and named a Polygon mirror, has six sharp corners, there are low and high pressure regions on each of six edges when it rotates. Therefore, the pressure difference generates three dimension flow field and causes aerodynamic noise. The Ffowcs-Williams and Hawkings (FWH) method is employed for the analysis. We have measured the sound pressure levels and compared them with the computational results. The calculated sound pressure levels agree well with the experimental results. We modified the shape of the edges of a hexagonal disk to reduce the noise level and confirm their effects through numerical computation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1148-1153
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• 2008

Noise pollution from a high speed train has been a serious social issue nowadays. Especially when a train speed exceeds 350 km/hr, an aerodynamic noise level has been known to be increased drastically. In this paper, explained were the studies on the noise reduction and engineering approaches to estimate and analyze influences of noise. Based on this study, it is estimated to apply results to development of trains and expected to accomplish futuristic technology by devising noise prediction of high speed EMU and measures to reduce noise on a design phase.

• 한국유체기계학회 논문집
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• 제20권2호
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• pp.26-31
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• 2017

In the present study, 20 kW turbine for OTEC with a ejector and a motive pump is designed and performance prediction is implemented by means of CFD. The meridional analysis for initial geometry and CFD for detail design are used to design the turbine. This turbine has about 90.9% efficiency and 28.47 kW power at 15,000 rpm and pressure ratio of 1.53. Homogeneous mixture model is used because two phase flow can be occurred in the turbine. Performance evaluation is carried out and then results are presented by plotting of power, mass flow rate and efficiency as varying pressure ratio and rotational speed.

• 대한기계학회논문집B
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• 제24권5호
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• pp.718-724
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• 2000

A model for depicting the rocket engine combustion process is presented and several experiments near a design point are provided with a FOOF type of unlike impinging injector for a propellant combination of Jet A-1 fuel and liquid-oxygen. The model is based on the assumption that the vaporization is the rate-controlling combustion process. The effects of initial drop size and initial drop velocity are systematically shown and discussed. It is seen that in the midst of considered parameters the change of initial drop size is more sensitive to the performance. The proposed model describes qualitative trends of combustion process well despite of its simplicity.

• 전기학회논문지
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• 제63권1호
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• pp.162-172
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• 2014

A three-dimensional dynamic model for simulating various motions of full vehicle is presented. The model has 16 independent degrees of freedom (DOF) consisting of three kinds of components; a vehicle body of 6 DOF, 4 independent suspensions equipped at every corner of the body, and 4 tire models linked with each suspension. The dynamic equations are represented in six coordinate frames such as world fixed coordinate, vehicle fixed coordinate, and four wheel fixed coordinate frames. Then these lead to the approximated prediction model of vehicle posture. Both lateral and longitudinal dynamics can be computed simultaneously under the conditions of which various inputs including steering command, driving torque, gravity, rolling resistance of tire, aerodynamic resistance, etc. are considered. It is shown through simulations that the proposed 3D model can be useful for precise design and performance analysis of any full vehicle control systems.

• 연구논문집
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• 통권22호
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• pp.5-19
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• 1992

An aerodynamic design technique of a centrifugal impeller is developed. The design procedure consists of a preliminary design, a three-dimensional blade surface generation, a flow analysis of impeller passage and a compatibility analysis for the designed impeller. To get a higher efficiency, the backswept impeller which has a lean angle and a parabolic blade surface is designed. In the present analysis of flow in an impeller, an inviscid quasi-three-dimensional method and a viscous three-dimensional method are used. Compatibility of the designed impeller is decided with the results of the analyses. The quasi-three-dimensional method is easy to use, but limited to a few conditions in real application for the prediction of the actual flow in the impeller. Since the viscous three-dimensional method proved to predict the real flow in the impeller relatively well, it can be used as a means for the decision of compatibility of the designed impeller.

• 한국군사과학기술학회지
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• 제2권2호
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• pp.70-82
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• 1999

During the aircraft conceptual design stage, rapid aerodynamic analyses over various configurations are required. Hence, empirical and analytical methods play important roles in predicting the aero-dynamic characteristics. In this study, total drag estimation method based on empirical and analytical approaches is developed. By comparing with the results of the wind tunnel experiment and existing prediction methods, it is demonstrated that the developed method is accurate and useful in predicting total drag for the whole Mach number range.

• 한국군사과학기술학회지
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• 제16권4호
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• pp.481-485
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• 2013

Rotor wake causes unsteady aerodynamics of rotor blade. So, accurate prediction of wake is very important and vortex method is good solution for this problem. Aerodynamic force of the rotor blade is calculated by potential panel method and the rotor wake is simulated by vortex particle method. The vortex particle method is easier to treat wake-body interaction and has better performance to expect the effect of ground and fuselage interaction. Rotor in hovering and forward flight condition is simulated through these methods. Thrust and surface pressure of rotor are compared with experiment data.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.168-171
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• 2005

The present study describes the prediction of the flow induced noise level of a high-speed rotating hexagonal disk and proposes the way how to reduce it. Since a hexagonal disk, which is used in the laser printer and named a polygon mirror, has six sharp comers, there are low and high pressure regions on each of six edges when it rotates. Therefore, the Pressure difference generates three dimension flow field and causes aerodynamic noise. The Ffowcs-Williams and Hawkings(FWH) method is employed for the analysis. We have measured the sound pressure levels and compared them with the computational results. The calculated sound pressure levels agree well with the experimental results. We modified the shape of the edges of a hexagonal disk to reduce the noise level and confirm their effects through numerical computation.