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상부패드의 형상 변경을 통한 'Anti-fluttering 틸팅패드 저널베어링' 개발
양승헌,나운학,박희주,김재실,Yang, Seong Heon,Nah, Un Hak,Park, Heui Joo,Kim, Chaesil 한국유체기계학회 2005 한국유체기계학회 논문집 Vol.8 No.5
The tilting pad journal bearings have been widely used to support high pressure/high rotating turbine rotors owing to their inherent dynamic stability characteristics. However, fatigue damages in the upper unloaded pads and the break of locking pins etc. by pad fluttering are continuously taken place in the actual steam turbines. The purpose of this paper is to develop a new bearing model that can prevent bearing problems effectively by pad fluttering in a tilting pad journal bearing. A new bearing model which has a wedged groove is suggested from the studies of fluttering mechanism performed by previously research works. The fluttering characteristics of the upper unloaded pad are studied experimentally in order to verify the reliability of a new bearing model. It can be known that the phenomenon of pad fluttering nearly does not occurred in the new bearing model under the various experimental conditions. And it is observed that any kinds of bearing failures by pad fluttering does not detect in the application of acture steam turbines.
그래픽 환경을 이용한 상호 대화 방식의 증기 터빈 회전의 설계 패키지 개발
임형근(Hyoung-Keun Lim),박구하(Koo-Ha Park),나운학(Un Hak Nah),장근식(Keun-Shik Chang) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
The steam turbine rotor blade is designed using the Turbine Rotor Design Package developed by the authors. It can quickly accomplish blade shape design in the power plant industry. The quasi-3d code is employed for analysis of passage flow in the blade sections. Iterative change of each blade shape is made by moving position of control points in the Bezier curve under GUI(graphic user interlace) environment. The full 3-D blade shape is obtained by stacking of the section blades.
550MW급 초초임계압(USC, ultra super critical) 증기터빈의 Spike Vibration에 관한 원인 규명 및 대책
양승헌(Yang, Seong-Heon),김용석(Kim, Yong-Seok),나운학(Nah, Un-Hak),박종권(Park, Jong-Geun) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.12
A very abnormal vibration was occurred at the LP(low pressure) turbine continuously during the pre-operation for a 550MW class USC(ultra super critical) steam turbine. This vibration was initiated at the rotating speed of about 3,450 rpm and then the vibration amplitude was highly increased the number by $2{\sim}3$ times with the increase of the rotating speed to the rated speed (3,600 rpm). In this paper, this abnormal vibration named spike vibration. This spike vibration was caused by the rubbing between the rotating bucket tip seal and the lower half of spill strip. Also, this paper presents the mechanism of the spike vibration and the proper method to eliminate this abnormal vibration problem. This result would be good practice to find the solution of similar high vibration in the USC steam turbines for power plant as well as industrial rotating machineries.