Light and short arc rubs in rotating machines: Experimental tests and modelling

• Published in: Mechanical systems and signal processing Vol. 23; no. 7; pp. 2205 - 2227
• Main Authors: Pennacchi, P., Bachschmid, N., Tanzi, E.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2009; Elsevier
• Subjects: Applied sciences; Drives; Exact sciences and technology; Experimental tests; Fundamental areas of phenomenology (including applications); Machine components; Measurement and testing methods; Mechanical engineering. Machine design; Modelling; Physics; Rotordynamics; Rub; Seals and gaskets; Shafts, couplings, clutches, brakes; Solid mechanics; Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Rotordynamics; Modelling; Experimental tests; Rub; Measuring machine; Rotating machine; Turbine rotor; Compressor; Mechanical clearance; Rotary seal; Experimental study; Modeling; Pump; Shaft; Signal processing; Non linear effect
• ISSN: 0888-3270; 1096-1216
• DOI: 10.1016/j.ymssp.2009.03.008

Rotor-to-stator rub is a non-linear phenomenon which has been analyzed many times in rotordynamics literature, but very often these studies are devoted simply to highlight non-linearities, using very simple rotors, rather than to present reliable models. However, rotor-to-stator rub is actually one of the most common faults during the operation of rotating machinery. The frequency of its occurrence is increasing due to the trend of reducing the radial clearance between the seal and the rotor in modern turbine units, pumps and compressors in order to increase efficiency. Often the rub occurs between rotor and seals and the analysis of the phenomenon cannot set aside the consideration of the different relative stiffness. This paper presents some experimental results obtained by means of a test rig in which rub conditions of real machines are reproduced. In particular short arc rubs are considered and the shaft is stiffer than the obstacle. Then a model, suitable to be employed for real rotating machinery, is presented and the simulations obtained are compared with the experimental results. The model is able to reproduce the behaviour of the test rig.