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1、A Brief History andState of the Art of Rotor DynamicsBylr. Rajh TiwarlDvpurtmeM of Mechanical EngineeringIndian Institute of Technology* GuMahati 781039Under AICTtL Spon.red Q1P Short l erm Course ohTheory & Practice of Rotor Dynamics(15-19I IT GuwahatiDr R TiuwiiniOutline of the Presentation Inlrud
2、uctiovi arid Definition Historyfrom Rakine (1869) to Jeffcott (1919)from Stodola (1924) to Lund (1964)from Dimentberg (1965) to till now Development of RotoDynamics Analysis ToolsSoftwares for Rotor Dynamics AnalysisDr R Tiuwi miwAriCdZgeuk iniOutline of the Presentation Dynamic Balancing of Rotors
3、Condition Monitoring of Rotating Machineries Con elusions & Recent T rendsDr R TiuwiinIntroductio n A brief history of rotor dynamics field has been documented in the present review paper. It reviews early development of simple rotor models, analyses tools, and physical interpretations of various ki
4、nd of instabilities in rotor-bearing systems. It also reviews developments of analysis methods for the continuous and multi-degrees-ol freedom systems that allowed practicing engineers to apply these methods to real turbomachineries.The paper also summaries work on dynamic balancing of rotors, vibra
5、tion based cond帀oning monitoring, and recent trends in the area of rotor dynamics.Dr R Tiuwi 仮iunriFiZcmct in)Introduction A rotor is a body suspended through a set of cylindrical hinges or bearings that allow it to rotate freely about an axis fixed in space- Engineering components concerned with th
6、e subject of rotor dynamics are rotors in machines, especially of turbines, generators motors compressors, blowers and the like. The parts of the machine that do not rotate are referred to with general definition of stator. Rotors of machines have, while in operation, a great deal of rotational ener
7、gy, and a small amount of vibrational energy.Dr R TiujriiniIntroductio n It is very evident from the fact that a relatively small turbine propels a huge aircraft.The purpose of rotor dynamics as a subject is to keep the vibrationai energy as small as possible. In operation rotors undergoes the bendi
8、ng, axial and torsional vibrations.一?History of rotor dynamicsfrom Rakine (1869) to Jeffcott (1919) Rotor dynamics has a remarkable history of developments, largely due to the interplay between its theory and its practice, Rotor dynamics has been driven more by its practice than by its theory. This
9、statement is particularly rele/ant to the early history of rotor dynamics Research on rotor dynamics spans at least 14 decades of history.Dr R Tiuwi (ftiuariwiitjiefikK iniSingle Mass Rotor Models乞=487心A flrxihk rotor mounted on rigid bearingsA rigid rot(r mounted on flexible ben ringsF=F sindXAn c(
10、|uivnknt single degree orrrecdomprinmass systemDr TiuMiini Rankine (1869) performed the first analysis of a spinning shaft He chose a two-degrees-of-freedom model consisted of a rigid mass whirling in a orbit, with an elastic spring acting in the radial diection. He predicted that beyond a certain s
11、pin speed ： the shaft is considerably bent and whirls around in this bent form： He defined this certain speed as the whirling speed of the shaft. In fact, it can be shown that beyond this whirling speed the radial defection of Rankine*s model increases without limit.Rankhic rulvr mvdvl dcjrcv rrtrdo
12、tii H|rin|t-ntMwS roht model) Today, this speed would be called the threshold speed for divergent instability However, Rankine did add the term whirling to the rotor d 师$国血敝watKuia砒.Krrc hixl) di味mm of the iiNMirl Rankme s neglect of Coriolis acceleration led to erroneous conclusions that confused e
13、ngineers for one-half century. Whirling refers to the movement of the center of mass of the rotor in a plane perpendicular to the shaft.A critical speed occurs when the excitation frequency (e.g.t the spin speed of unbalnced shaft) coincides with a natural frequency： and can lead to excessive vibrat
14、ion amplitudes3=% =Dr R Tiuwi mhMrieiiy in)A Jcffcott (or Laval) rotor model in general whirling motionDr R Tiuwi mhMrieiiy in) The turbine built by Parsons in 1884 (Parsons, 1948) operated at speeds of around 18.000 rpm. which was fifty times faster than the existing reciprocating engineIn 1883 Swe
15、dish engineer de Laval developed a single-stage steam impulse turbine (named after him) for marine applications and succeeded in its operation at 42,000 rpm He aimed at the self-centering of the disc above the critical speed, a phenomenon which he intuitively recognized He first used a rigid rotorf but latter used a flexible rotor and showed that it was possible to operate above critical speed by operating at a rotational speed about seven times the critical speed (Stodola, 1924).Dr R TiuMini It thus became recognized that a shaft has several critical speeds
