Tham khảo tài liệu 'hydrodynamic lubrication 2011 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 92 5 Stability of a Rotating Shaft Oil Whip Table . Rotor dimensions Rotor l m Ip Id N N L R c ụ mm kg kg-mm kg-mm rpm rpm mm mm mm mPa-s _A 1000 10 10 5 1893 3383 15 30 20 B 680 10 10 5 3376 5445 15 30 20 l shaft length m disk mass Ip Id moment of inertia Nc critical speed Ns stability limit L bearing length R bearing radius c bearing clearance ụ viscosity identical A type rotors from Table and the rotors in Fig. bb consist of a rotor B and a rotor A from the same table. The displacement of bearing normalized by the bearing clearance is taken on the horizontal axis and the symbol for each curve gives the direction of displacement of the bearing taken every 30 from the vertical downward direction 0 to 150 in the direction of shaft rotation. In the Fig. ba where two identical rotors are coupled the stablity limit curve is symmetrical and the stability limit falls if the bearing is displaced from zero in any direction especially in the 30 direction. In Fig. bb where two different rotors are coupled the stability limit curve is asymmetrical and the stability limit is especially low in the direction of 30 . This requires special caution. The direction 30 may be related with the direction of the journal eccentricity. When the journal is displaced in the same direction but in the reversed sense the stability limit goes up a little. Influence of Earthquakes on Oil Whip Although there has been much research on earthquake-resistant design of structures such as buildings there is very little on that of machines including rotating machines. However machines such as generators are the cornerstones of human society and their earthquake-resistivity is very important. The influence of an earthquake on oil whip in rotating machines is considered here. As stated so far the stability calculation of a rotating shaft has usually been performed using linear theories. However this is inadequate to discuss the influence of a big disturbance .
