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나운학(U.H.Nah),조성일(S.I.Cho),신훈(H.Shin),김영상(Y.S.Kim),양승헌(S.H.Yang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
For many years, T/G Supplier has constructed a number of thermal power plants and researched to<br/> improve the performance and the reliability of steam turbine, which are achieved by advances in design and<br/> materials technology. In recent, interest is renewed in advanced steam condition as means of improving<br/> economy of thermal power plant and reducing environmental pollution. Improvements in the maximum power<br/> have been driven by the development of advanced rotor and bucket material and longer last stage bucket.<br/> Improvements in efficiency have been brought through advances in mechanical efficiency and<br/> thermodynamic efficiency. This paper describes a number of new steam path design features introduced to the<br/> steam turbine product. And also this paper describes new design technologies' development, new<br/> technologies' trend and technologies' development for ultra-super critical steam turbine.
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.
USC 증기터빈용 LP Exhaust Hood 유동특성
이병은(Byeong E. Lee),김진환(Jin W. Kim),박구하(Koo H. Park),나운학(Un H. Nah),이수언(Soo E. Lee) 한국유체기계학회 2004 유체기계 연구개발 발표회 논문집 Vol.- No.-
CFD analysis has been performed to investigate flow behavior in LP exhaust hood of steam turbines and evaluate exhaust loss, which is directly related to the steam turbine performance, in it. Development of the optimum shape of LP exhaust hood has been done with an improved shape of steam guide, which plays a key role in terms of cost as well as performance. The newly developed LP exhaust hood will be applied for a large USC steam turbine having a capacity of 1,000 ㎿.
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.