A comparative study of the dynamic stability of a rotor supported by an air-bearing and an air-ring bearing

DYNAMIC STABILITY OF AIR-BEARING AND AIR RING BEARING

Abstract

An exploration to justify the need for an air-ring around an air-bearing is done by comparing the dynamic stability plots of a rotor supported by air-bearings with and without an air-ring. Air-bearing with air-ring or air-ring bearing (ARB) has pocketed feed-holes. The air-bearing without air-ring has plain feed-holes and it is referred to as air-bearing with a direct feeding system (ABDFS). A linearized free-vibration model rotor-bearing is used to analyze the dynamic stability. The dynamic coefficients of ABDFS and ARB are affected by whirl frequency due to the fluid compressibility effects. The stability threshold speed of the rotor air-ring bearing system (RARBS) is increased well above the threshold speed of the rotor air-bearing with a direct feeding system (RABDFS). The rotor critical mass of RARBS is smaller than that of RABDFS. The air-ring of ARB can prevent self-excited vibration in lightly loaded rotor-bearing systems.