A Novel Weldless Foils-Case Attachment for Gas Foil Bearings

Gas Foil Bearings (GFB) have a wide field of applications, from air cycle machines to microturbomachinery. A GFB basically consists of a foil (top foil) that lies over a corrugated foil (bump foil) that acts as a compliant spring. The rotation of the shaft introduces the fluid into the bearing and the pressure generated into the gap between the shaft and the top foil supports the rotor. The foils are attached to the case in a fixed point; usually they are welded to the bearing case. In addition to being rather cumbersome to build, this welded union is a potential point of failure. This work presents a new proposal of foils and case union. Foils are not welded to the case; they are placed or slid into a groove which avoids the strain concentration. This also permits the replacement of any foil in case of damage and to change the bump foil to modify the load capacity or the rotordynamic coefficients if required. The proposed assembly is experimentally tested by measuring its static stiffness in different radial directions of the fixed point. Results for static stiffness are presented and discussed.