• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.775-780
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• 2013

In recent years, a notebook like an ultrabook gets thinner. Its thickness causes problems in cooling fan performance, system installation condition, and so on. In this study, we installed a small turbofan in notebook system with very narrow gap in order to generate similar condition to a real product. Experiments were performed to measure the fan's performance and the flow and noise characteristics, its results were compared with computational ones. Prediction of P-Q curve using CFD showed under about 5% error in high flow rate and its trend was agreed with experimental one over the flow field. Experimental data to measure the noise at a distance of 100 mm from a rotation axis direction of an impeller corresponded well with computational ones of broadband and BPF noise. The noise experiments to measure at a distance of 100 mm from a rotation axis direction of an impeller corresponded well with computational ones of broadband and BPF noise. Especially, tip part of impeller blade and part of exit and bottom near in an analysis by a commercial program(FlowNoise).

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.25-29
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• 2005

Axial fan is used for the supplement of large amount of flows. Axial blowers show relatively high efficiency of the system. The present model of axial fan is for cooling a condenser in an air-conditioning unit that exhibits tendency toward compact size. In order to realize the compact model, the width of an axial blade should be cut down in axial distance. Main interest lies on the performance of the axial blowing system with blades having shorter chord length. One of the important design parameters for axial fan is the shape of the blades of it. Design of blades includes the cross-sectional shape and its dimension, including the chord length. We consider two types of blades; one is NACA airfoil with normal chord length and the other is with shortening chord length by $10\%$ of normal airfoil. Axial blower with the modified blades is essential for the compact model of an air-conditioner. The other design parameters are same in the two cases. Using a wind tunnel follows ASHRAE standards carries out evaluation of performance of the system. Detail of flows around the blades is prepared by velocity measurements using PIV. According to performance estimation, the axial blower with short chord blade show quite close to the performance results, including flow rate and pressure rise, of the standard one. The reason of the two similar results is that the flowpatterns depend on Reynolds number based on the chord length of a blade. In this investigation, the critical chord length is found, in which the flows near the airfoil are so unstable and the performance of the system is decreased. A series of figures is for the detail information on the flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.268-276
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• 2005

The aim of this paper is to suggest one efficient method for the various requirements of performance during the process designing and producing an impeller. The study considers that the revisions of a pitch angle of an impeller at an axial turbo fan affect an air flow rates and a static pressure rise. The axial turbo fan specified with the 250 Pa maximum static pressure and 1300 CMH fan air flow rates was tested and analyzed by CFD. The Numerical results show that the air flow rates are calculated to 1,175 CMH, 1,223 CMH, 1,270 CMH, 1,340 CMH and 800 CMH in cases that the pitch angles are $44^{\circ},\;49^{\circ},\;54^{\circ},\;59^{\circ},\;and\;64^{\circ}$ respectively. Also the static pressure rises are shown to 108 Pa, 122Pa, 141 Pa, 188 Pa and 63 Pa at the same cases. The air flow rate is increased linearly according to the changes of the pitch angle from $44^{\circ}\;to\;59^{\circ}$ and the maximum air flow rate passing the impeller is increased to $13\%$ over at the case of $59^{\circ}$ pitch angle compared with the reference case of $54^{\circ}$ pitch angle. The static pressure rise is increased linearly according to the changes of the pitch angle from $44^{\circ}\;to\;54^{\circ}$, too. The static pressure rise at the $59^{\circ}$ pitch angle is increased to $33\%$ over compared with the $54^{\circ}$ pitch angle. The result shows that the revisions of pitch angle make the static pressure rise increase widely. However the air flow rates and the static pressure rise at the $64^{\circ}$ pitch angle are suddenly decreased because of over-changed pitch angle.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.52-61
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• 2015

This paper performed a numerical study to analyse the transient performance behavior of a turbofan engine with variable inlet guide vane (IGV) and bleed air schedules. The low bypass ratio mixed flow turbofan engine was considered in this study. For modeling the compressor performance with IGV, the performance maps were generated by using a one-dimensional meanline analysis and feed to the engine simulation program. The IGV and bleed air according to the rotating speed were scheduled to satisfy 10% of surge margin at steady-state condition. The transient engine performance analysis was conducted with the schedules. The engine with IGV schedule showed a higher surge margin and lower turbine inlet temperature than the engine with bleed air schedule during the transient period.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.3
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• pp.1-8
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• 2009

This thesis has analyzed the effect of the surge happening in flight on the engine performance, especially on the PW4000 turbofan engine. It is to be judged that the flight surge can occur more often at the time of takeoff than it does en route due to the fact that the engine parameters are prone to fluctuate. EPR is judged to be the most highly sensitive parameter responding when surge occurs. Both Engine rpm and Wf decrease almost simultaneously just like an EPR. During the take-off rolling, N1 vibration is more sensitive than the N2 vibration. Consequently, the surge can be detected by EGT increase, while the other parameters (EPR, rpm, Wf, etc) decrease.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.236-239
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• 2008

This thesis has analyzed the effect of the surge happening in flight on the engine performance of the PW4000 turbofan engine. EPR is judged to be the most highly sensitive parameter responding when surge occurs. Both N1 rpm and N2 rpm decreases almost simultaneously just like an EPR. During the take-off rolling, the N1 vibration is more sensitive than the N2 vibration. Consequently, the surge can be detected by EGT increase, while the other parameters decrease.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.117-124
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• 2018

This paper describes the localization development of an axial fan for KM-SAM multi-function radar. The multi-function radar, which is constantly affected by the external environment, is a key instrument for detecting and tracking low and medium altitude threat targets. Operating this equipment smoothly requires a fan for controlling the internal temperature and humidity. Presently, all such fans are imported. To solve these problems, localization development research was proposed. The development of localization includes analysis of requirements through review of related technical reports such as original equipment and system equipment specification, prototype design, and verification of design requirement through performance test and environmental test. The study results are described. The blower consisted of an axial fan with guide vanes and the motor was designed to generate a maximum airflow of 970 CFM and a wind pressure of 4.8 IWG. Six prototypes were manufactured for performance evaluation. In addition, for reliable data acquisition, AC power supply, fan performance tester and data acquisition equipment were designed and tested. All prototypes were verified as having design requirements equal to or better than those of imports.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.36-45
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• 2015

Recently, a lot of studies have been made about the methods used to generate turbulent velocity fields stochastically in order to effectively predict broadband flow noise. Among them, the FRPM (Fast Random Particle Mesh) method which generates turbulence with specific statistical properties using turbulence kinetic energy and dissipation obtained from the steady solution of the RANS (Reynolds Averaged Navier-Stokes) equations has been successfully applied. However, the FRPM method cannot be applied to the flow noise problems involving intrinsic unsteady characteristics such as centrifugal fan. In this paper, to effectively predict the broadband noise generated by centrifugal fan, U-FRPM (unsteady FRPM) method is developed by extending the FRPM method to be combined with the unsteady numerical solutions of the unsteady RANS equations to generate the turbulence considered as broadband noise sources. Firstly, an unsteady flow field is obtained from the unsteady RANS equations through CFD (Computational Fluid Dynamics). Then, noise sources are generated using the U-FRPM method combined with acoustic analogy. Finally, the linear propagation model which is realized through BEM (Boundary Element Method) is combined with the generated sources to predict broadband noise at the listeners' position. The proposed technique is validated to compare its prediction result with the measured data.

• Proceedings of the Korea Contents Association Conference
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• 2011.05a
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• pp.553-554
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• 2011

자동차, 선박, 기계부품 등의 분야에서 고성능 컴퓨터를 활용한 공학 시뮬레이션 기술은 이미 널리 활용되고 있으며, 바이오, 나노뿐 아니라 금융 분야까지 확대되고 있는 추세이다. 공학 시뮬레이션을 수행하기 위해서는 CFD(Computational Fluid Dynamics), 기계구조, 병렬수치해석 등에 대한 고급 지식이 요구되는데, 이로 인해 산업체에서의 활용이 활발하지 못한 것이 현실이다. 이러한 문제를 해결하기 위한 하나의 대안으로 공학 시뮬레이션 프로세스의 자동화 기술이 등장했으며, 열유체, 피로내구, 진동, 충돌 등의 분야에서 특정제품이나 기술에 대한 시스템이 제안되었다. 국내에서는 에어포일(airfoil), 팬(fan), 기어(gear) 등의 제품이나 주조 기술에 대해 공학 시뮬레이션 자동화가 시도되었다. KISTI에서는 축류팬(axial fan) 시뮬레이션 자동화에 대해 프로토타입 시스템을 구축하였으며, 현대차에서는 자동차 부품에 대한 시뮬레이션 자동화 시스템을 구축하여 활용하고 있다. 미국 OSC(Ohio Supercomputer Center)의 경우 용접기술에 대한 시뮬레이션 자동화 시스템을 웹상에 구축하여 서비스를 오픈하였으며, 현재 전 세계 200여 기업이 이용하고 있다. 공학 시뮬레이션 자동화 기술이 보다 발전하기 위해서는 시뮬레이션 결과의 신뢰성, 적용 가능 분야 및 제품의 확대, 데이터보안 등이 확보되어야 한다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.749-762
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• 2019

In recent years, in urban areas, underground of roads are being promoted in order to resolve traffic congestion and to secure green spaces, and due to the low ratio of large vehicles, they are planned or constructed as road tunnels for small cars only. In addition, the tunnels being built in the city is a tendency to be enlarged to play the role of main roads. Accordingly, the capacity of the ventilation system is increasing and various ventilation methods are required, and the importance of maintenance after the completion of the tunnel such as the operating cost of the ventilation system is emphasized. Therefore, the need for optimization of the operation stage for reducing the power consumption of the ventilation system and the study of the ventilation system operation control logic is increasing. In this study, the study on the necessity of the optimization of operation stage and control logic of the ventilation system was carried out to realize the energy-saving operation for the small car only passing through tunnels which is applied of ① jet fan and combination ventilation system (② jet fan + air purifying equipment, ③ jet fan + vertical shaft, ④ jet fan + supply air semi-transverse). As a result of this study, there can be various operating combinations in the case of the combined ventilation system, and even though the amount of ventilation air is the same, the operating power varies greatly according to the operating combinations. It was found that operating the axial fan first rather than the jet fan first operation method has an effect on power saving.