Optimization of Rotor Critical Speeds by Change of Features of Machine’s Bearings

The subject of this article is an analysis of the influence of changes of certain construction and operation parameters of slide bearings on the critical speeds and corresponding forms of vibrations of rotors supported in such bearings. An exemplary analysis has been made for a typical, average sized turbo-compressor train consisting of three rotors. It has been found that critical speeds of a rotor are most sensitive to the bearings clearance; less sensitive to the bearings length, and least sensitive to the oil mean temperature. Found relations permit to avoid an accidental search for a way to change the rotor critical speeds if there is such a necessity and when it is impossible to change the geometry of the rotor itself. The results of the analysis allow optimization of the process of detuning the machine from resonance.