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SI 엔진의 스로틀 밸브에서 유동장 특성에 대한 실험해석
김성초,김철,최종근,이석정,Kim, Sungcho,Kim, Cheol,Choi, Jonggeun,Lee, Seokjeong 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.7
Experimental investigations on the flow characteristics of downstream region of a butterfly valve, which is used in SI engine, have been conducted according to Reynolds number and valve angle. Measurement programs of the flowfield using x-type of hotwire anemometry include the mean and fluctuating velocity, turbulnet intensity, shear stress, power spectrum and pressure loss coefficient. Experimental results show that flow characteristics and independent of relatively high Reynolds number; 60,000 and 80,000. It is also seen that streamwise mean velocities have relatively large velocity gradient around the butterfly valve with increasing the valve opening angle and this trend appears even in the far downstream region. The distributions of turbulent intensity and shear stress show irregular behavior regardless of the valve opening angle and those of the case of the valve opening angle of 45°are the largest. The pressure loss coefficient of the body surface of the throttle valve increases mildly with the increase of Reynolds number and increases rapidly with the reduction of the valve opening angle.
역설계에 의한 비행기의 형상 구현과 수치계산에 의한 유동 가시화
김양균(Yangkyun Kim),김성초(Sungcho Kim),김정수(Jeong Soo Kim),최종욱(Jongwook Choi),박정(Jeong Park) 한국가시화정보학회 2007 한국가시화정보학회지 Vol.5 No.2
The geometry of a commercial passenger airplane is realized based on a Boeing 747-400 model through the photographic scanning and reverse engineering. The each element consisting of the plane such as fuselage, wing, vertical fin, stabilizer and engines, is individually generated and then the whole body is assembled by the photomodeler. The maximum error in the realized airplane is about 1.4% comparing with the real one. The three-dimensional inviscid steady compressible governing equations are solved in the unstructured tetrahedron grid system, and in a finite volume method using STAR-CD when the air-plane flies at the cruise condition. The pressure distribution on the surface and the wing-tip vortices are visualized, and in addition to the aerodynamics coefficients, lift and drag are estimated.
김수연(Suyean Kim),최종욱(Jongwook Choi),김성초(Sungcho Kim),김정수(Jeong Soo Kim) 한국가시화정보학회 2008 한국가시화정보학회 학술발표대회 논문집 Vol.- No.2
회전익기 중 일반적인 헬리콥터는 단일 로터 블레이드로 구성되어 있다. 그리고 동체의 모멘트를 보정해 주기 위하여 꼬리 회전익이 필요하다. 이에 반해 동축반전 회전익기는 꼬리 회전익이 필요가 없을 뿐만 아니라 단일 로터 블레이드 회전익기 보다 더 높은 추력을 나타낸다. 한편, 단일 로터 시스템에 덕트를 장착할 경우 일반적으로 더 높은 추력과 안전성을 확보할 수 있다. 본 연구에서는 단일덕트와 트윈덕트를 포함한 동축반전 블레이드 주위의 유동해석을 수행하였다. 수치해석 결과, 트윈덕트를 장착한 동축반전 시스템이 단일덕트 혹은 덕트가 없는 동축반전 시스템보다 추력계수가 더 높게 나타났다. 이와 같은 공력특성 및 유동해석 결과는 기존의 동축반전 시스템의 효율개선 및 안전성 확보에 도움이 될 것으로 기대된다.
김양균(Yangkyun Kim),김성초(Sungcho Kim),김정수(Jeong Soo Kim),이기만(Kee Man Ree),진학수(Haksu Jin) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Flow and aerodynamic characteristics were analyzed numerically for a commercial passenger airplane, Boeing 747-400, flying in the cruising condition. The model geometry with 100:1 in scale was obtained by the photo scanning measurement with the maximum error of 1.4% comparing with the real airplane dimension. The three-dimensional inviscid steady compressible governing equations were solved by the finite volume method in the unstructured grid system. The convective terms were treated by the Crank-Nicholson and first-order upwind schemes. In the computational results, the strong wing-tip vortices were clearly observed and the pressure contours on the airplane surface were suggested. The lift and drag forces in the wing with engines increase by 1.49% and 3.9%, respectively compared with the case without engines. The aerodynamic forces were estimated quantitatively for each element which consists of the airplane.