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원심 전향익 송풍기 날개 후단의 형상에 따른 소음 분석
김휘중(H.-J. KIM),정근화(K.-H. JUNG),이창준(C.-J. LEE),이승배(S. LEE) 한국유체기계학회 2000 유체기계 연구개발 발표회 논문집 Vol.- No.-
The turbulent broadband sound power from a forward curved bladed fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer on the blade. This paper reports the effects of the solidity (C/S) and the stagger angles upon the trailing edge noise with respect to the trailing edge shapes of circular-are cambered blade of multi-bladed fan, and discusses the major physical mechanism of reduced noise for the circular trailing-edged case.
트럭 및 대형버스용 튜브리스 래디얼 타이어의 비드부 크랙 발생 메카니즘 연구
김휘중(H.J.Kim),김종백(J.B.Kim),장윤태(Y.T.Jang),송의환(Y.H.Song) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2
In this study, rim temperature rise produced due to the heated brake system of trucks and buses is measured. Its contribution to the bead crack failure of tubeless radial tires is examined. An equipment which can control the control the temperature of rim flange is designed tobe set-up in a bead endurance test machine. Bead failure initiation time is then measured at various temperature. A device that can induce air blowing into the gap between rim and brake drum has been developed in order to keep cooling down the rim. With the air cooling device, the temperature of rim flange can be reduced by about 15℃ at most, which can prevent much of tire failure.<br/>
LES를 이용한 NACA0018 에어포일 주위의 유동 및 이산소음계산
김휘중(H.-J. KIM),이승배(S. LEE) 한국유체기계학회 2002 유체기계 연구개발 발표회 논문집 Vol.- No.-
The flow field around a symmetrical airfoil in a uniform flow under the generation of noise was numerically studied and compared with experimental datum. The numerical simulation was carried out by LES which employs a deductive dynamic model as subgrid-scale model. The result of an attack angle of 6° indicate that the discrete frequency noise is generated when the separated laminar flow reattaches near the trailing edge of the pressure side and the turbulent boundary layer is formed over the suction side of the airfoil near the trailing edge. The periodic behavior of vortex formation was observed around the trailing edge and it persists further downstream in the wake. The frequency of the vortex formation in the wake was consistent with that of the discrete frequency noise.