STABILITY OF ROTORS SUPPORTED IN GAS-BEARINGS WITH BUSHES MOUNTED IN AIR RINGS

When during the operation of rotors supported in gas bearings their ro tational velocity reaches a sufficiently high value, the loss of stead y-state stability occurs. This instability is caused by the loss of da mping properties of the gas film, which leads to self-excited vibratio ns. These vibrations are the basic obstacle to a widespread applicatio n of gas bearings. The phenomenon of self-excited vibrations can be av oided by introducing an elastic supporting structure between the beari ng bushes and the casing, characterised by properly selected stiffness and damping coefficients. In practice such a structure can have the f orm of an externally pressurised gas ring. In this paper we demonstrat e, on the basis of selected examples, which ranges of the values of st iffness and damping coefficients of the gas ring make it possible to r etain steady-state stability at practically any rotational velocity of the rotor. We also show a design of the ring structure, especially of its feeding system, which ensures the required values of stiffness an d damping coefficients (with regard to the stability). Our investigati ons have been carried out by means of a numerical simulation method wi th the use of a mathematical model of the gas bearing, verified alread y many times.