MODELLING AND ANALYSIS OF ROTATING SYSTEMS WITH GAS FOIL BEARINGS UNDER TRANSIENT OPERATING CONDITIONS

摘要

Gas foil bearings are on the cutting edge of bearing systems that spread worldwide. Although it is a common practice to apply such systems to high-speed fluid-flow machinery, their modelling and analysis still pose a number of problems. This article describes the methodology used to assess dynamic properties of a rotor-bearings system supported by foil bearings. Particularly close attention has been paid to the system operation in a transitional state during which a gaseous lubricating film is formed. The conception for the description of the rotor support characteristics was implemented in a computer program that is still under development. The approach that has been taken makes it possible to analyse the system properties throughout a whole range of rotational speeds. Another approach used in the past enabled for analyses of the dynamic performance of rotors, but only on the condition that bearing operation is correct (i.e. only fluid friction in bearing is present). The new model allows for much broader analyses of bearings operation, as confirmed by the obtained results. The article discusses exemplary results of analyses and shows a way one can assess the dynamic properties of rotating machinery equipped with foil bearings even when analysed under transient operating conditions.