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원주방향 급유홈 프로팅링 저널베어링으로 지지된 탄성 회전체의 안정성
정연민,김경웅 대한기계학회 1992 대한기계학회논문집 Vol.16 No.12
The stability of the flexible rotor mounted on circumferentially grooved floating ring journal bearings was investigated theoretically and experimentally. The floating ring journal bearing was analyzed by using JFO reformation boundary condition. The flexible shaft was analyzed by the finite element method based on Rayleigh beam theory. It was found that the measured ring speed agrees well with the theoretical results. The instability of the system due to not only the outer film but also the inner film of the bearing could be predicted by the theory which allows negative vapor pressure. The tendency that reducing the supply pressure of lubricant stabilizes the system was observed both experimentally and theoretically. 본 연구에서는 동 베어링에 대한 해석을 바탕으로 원주방행 급유홈 프로팅링 저널베어링으로 지지된 탄성 회전체의 안정성에 대한 이론을 전개함과 동시에 실험을 통해 동 베어링의 안정성을 조사하고자 한다.
회전하는 제어원주가 설치된 원주후류의 유동장에 관한 연구
부정숙,류병남,심정훈 한국마린엔지니어링학회 2000 한국마린엔지니어링학회지 Vol.24 No.3
An experimental study was conducted to investigate the influence of the spinning control cylinders which was set on the surface of a fixed circular cylinder in uniform flow, $Re=1.24\times10^4$. The measurements of velocity vectors and pressure distributions are carried out in various spin parameters and angles of spinning control cylinder. The results show that velocity profiles and pressure distributions are different with angles of control cylinder and spin parameters. When the control cylinder angle is $100^{\circ}$, there is more effect in increasing the velocity and the pressure distribution than other cases. In this case, the vortex shedding frequency was increased as increasing spin parameter.
균일류의 회전원주 제어에 의한 유동 및 공력 제어효과에 관한 연구
부정숙,양종필,김창수,신영곤,Bu, Jeong-Suk,Yang, Jong-Pil,Kim, Chang-Su,Sin, Yeong-Gon 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.3
The aerodynamic forces and wake structure of the non-rotating downstream circular cylinder, of which the uniform freestream flow is interfered with another spinning upstream cylinder having the same diameter that is located upstream in a line have been investigated experimentally. When the spin rate of the downstream cylinder defined as the ratio of tangential surface velocity of the spinning cylinder to the freestream velocity increases gradually from zero to 1.4, the change of surface pressure distribution, aerodynamic forces of the non-rotating downstream cylinder were measured in case of several distance ratios of 1.5, 3.0, and 4.5 defined as the ratio of distance between the centers of two cylinders to the diameter. The wake flow patterns behind the cylinder were also investigated in each case. From the present experiments, it has been found that the spin rate significantly influences the aerodynamic forces and near-wake flow phenomena of the downstream cylinder in such a way that the drag increases as the spin rate and distance ratio increase and the wake width increases as the distance ratio increases.
비접촉 회전 스테이지에의 구동 원리로서의 횡자속 원주형 유도 방법
정광석(Kwang Suk Jung),김효준(Hyo Jun Kim) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.10
Compared with linear induction principle, the transverse flux circumferential induction principle is suggested as a driving mechanism of the revolving stage, which can rotate contactlessly without any supporting structure. The stage realizes the integrated motion of levitation, rotation, and planar perturbation, using the two-axis forces, normally directed force of the air-gap and tangential force, of the induction drivers mounted on the stator uniformly. In this paper, the force generating mechanism of the stage is described in detail. First, the various core shapes generating the transverse flux are analyzed to guarantee the proper thrust force. And the vector force intensity of the circumferential induction driver constituting the stage is compared with that of the linear induction driver. Especially it is shown that the magnetic force of the suggested system can be modeled with the linear equivalent model, including the test verification.
강명훈,김광석,노기덕,Kang, Myung-Hun,Kim, Kwang-Seok,Ro, Ki-Deok 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.2
The flow around a rotating circular cylinder near a plane wall is investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique in the circulating water tank. The experimental parameters are the rotating direction of the cylinder. the space ratios $H/D(H/D=0.05{\sim}0.5)$ between cylinder and plane wall and the velocity ratios ${\alpha}({\alpha}=0{\sim}{\pm}2.0)$. In the case of clockwise, the lift on the rotating circular cylinder was increased with the reduction of the space ratios and with the velocity ratios, the upper separation point was more shifted in the rotating direction with them. In the case of anticlockwise, the absolute value of the lift on the rotating circular cylinder was increased with increasing the space ratios and the velocity ratios. the lower separation point was more shifted in the rotating direction with them.
강명훈(Myeong Hoon Kang),노기덕(Ki Deok Ro),박지태(Ji Tae Park),공태희(Tae Hue Kong) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The flow around a rotating circular cylinder near a plane wall is investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique in the circulating water tank. The experimental parameters are the rotating direction of the cylinder, the space ratios H/D(H/D=0.05~0.5) between cylinder and plane wall and the velocity ratios α(α=0~±2.0). In the case of clockwise, the lift on the rotating circular cylinder was increased with the reduction of the space ratios and with the velocity ratios, the upper separation point was more shifted in the rotating direction with them. In the case of anticlockwise, the absolute value of the lift on the rotating circular cylinder was increased with the space ratios and with the velocity ratios, the lower separation point was more shifted in the rotating direction with them.
엇갈림 배열에서 회전원주에 의한 정지원주의 공력 및 후류유동 제어
부정숙,류병남,심정훈 한국마린엔지니어링학회 2001 한국마린엔지니어링학회지 Vol.25 No.4
The aerodynamic forces and wake structures of the non-rotating downstream cylinder which is located behind the spinning upstream cylinder in tandem and staggered arrangement have been investigated by experimental method at Re= $1.32{\times}10^4$. The measurements of wake flow and pressure distributions of downstream cylinder are carried out in various spin parameters by combination of both longitudinal spacing rations L/d=1.5, 3.0, 4.5 and transverse spacing ratios T/d =0.0, -0.5, 0.5. For the present experiment, it has been found that the spin parameter of spinning upstream cylinder affect more easily the downstream cylinder in tandem arrangement than that in staggered arrangement.
증기발생기 전열관 곡관부 덴트와 원주방향 외경노치가 혼합된 와전류신호 특성분석
김창수(Chang-Soo Kim),박병호(Byong-Ho Park) 한국비파괴검사학회 2020 한국비파괴검사학회지 Vol.40 No.3
증기발생기에서 곡률반경이 작은 U-bend 전열관을 제작하기 위한 굽힘 공정에서 덴트와 유사한 기하학적 형상변화를 유발하게 되며, 곡률반경이 상대적으로 큰 전열관 보다 굽힘 응력이 크게 발생한다. 전열관에 생성된 기하학적 형상변화는 가동 중에 응력이 집중되는 요인으로 작용하여 응력부식균열이 발생되기 쉬운 환경이 되며, 기하학적 형상변화의 영향으로 결함의 와전류신호 중간 부위가 꺾인 형태로 나타나게 된다. 본 연구에서는 이러한 특성을 분석하기 위하여 증기발생기 전열관의 1∼3열의 곡관부에 덴트와 원주방향 외경노치를 가공하여 생성되는 와전류신호의 특성을 분석하였다. Bending process of the steam generator U-bend tubes with small radius of curvature results in geometric changes similar to a dent. Such a tube generates a greater bending stress than a tube with a large radius of curvature. The change in geometric shape generated in the tube acts as a factor in which stress is concentrated during operation, marking it an environment where stress corrosion cracking is likely to occur, and the eddy current signal of defect is distorted due to the geometric shape change, marking detection difficult. In order to understand these characteristics, the dent and circumferential external diameter notches were machined in the tube of 1 to 3 rows, and the characteristics of the eddy current signal were analyzed.
밀폐된 원통내부에서 회전체의 형상이 회전유동에 미치는 영향에 관한 실험적 연구
김유곤,박천수,Kim, Yu-Gon,Park, Cheon-Su 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.5
Two-dimensional, angle-resolved LDV(Laser Doppler Velocimetry) measurements of the turbulent rotating flow field in a confined cylinder have been performed. The configurations of interest are flows between a rotating upper disk with a rod attached by a disk or impeller($\theta$ = 45$^{\circ}$, 90$^{\circ}$) and a stationary lower disk in a confined cylinder. The mean flow velocity as well as the turbulent intensity of the flow field have been measured. The results show that the flow is strongly dependent on the position of the impellers or the disk, negligibly affected by the Reynolds number in turbulent flow. It is observed that the mixing effect of the axial flow impeller($\theta$ = 45$^{\circ}$) is better than that of the radial flow impeller($\theta$ = 90$^{\circ}$) or a disk.