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틸팅패드 저어널베어링의 유막 강성 및 감쇠계수에 대한 실험적 연구
하현천(Hyun Cheon Ha),양승헌(Seong Heon Yang) 한국유체기계학회 1998 유체기계 연구개발 발표회 논문집 Vol.- No.-
An experimental study is performed to investigate the frequency effects of the excitation force on the linear stiffness and damping coefficients of a LOP (load on pad) type five-pad tilting pad journal bearing with the diameter of 300.91 ㎜ and the length of 149.80 ㎜. The main parameter of interest in the present work is excitation frequency to shake the test bearing. The excitation frequency is controlled independently, using orthogonally mounted hydraulic exciters. The relative movement between the bearing and shaft, and the acceleration of the bearing casing are measured as a function of excitation frequency using the different values of bearing load and shaft speed. Measurements show that the variation of excitation frequency has quite a little effect on both stiffness and damping coefficients. Both direct stiffness and damping coefficients in the direction of bearing load decrease by the increase of shaft speed, but increase with the bearing load.
하현천(Hyun Cheon Ha),최성필(Seong Pil Choi) 한국유체기계학회 1998 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper describes the shaft vibration phenomena measured on a pump-turbine of a pumped storage power plant. The pump-turbine runs at a rotational speed of 450 rpm (7.5 ㎐). The power output (load) of the pump-turbine was varied from 100 to 300 ㎿ in the generating mode. It was found that the magnitude of the shaft vibration was highly dependent upon the power load. The vibration magnitude of the shaft vibration is very high in the middle load zone from 170 to 210 ㎿, elsewhere the vibration low. From vibration spectra, it was found that the frequency of major vibration in that load zone was 2.5 ㎐ which is approximately 34% of the shaft rotating speed in ㎐. This frequency component disappeared below and above that load zone. This subsynchronous vibration is caused by the flow induced disturbance due to spiral vortex flow downstream of the pump-turbine runner. Furthermore, it was found that shaft vibration was highly decreased due to the increase of bearing preload.