Optimizing hydrodynamic thrust bearings of Mitchell type

Abstract

In turbine systems (steam turbines, as well as cen� trifugal and axial compressors), considerable energy is consumed in overcoming friction in the thrust (axial) slip bearing. Therefore, optimal design of thrust slip bearings entails minimizing the power losses in fric� tion, with simultaneous gain in reliability. We see from the Hersey–Stribeck diagram (Fig. 1) that the minimum frictional losses fmin correspond to minimum gap hmin between the moving surfaces such that their microprojections are not in contact (point 1) [1–3]. In that case, however, operation of the slip bearing is not reliable, since even small increase in the load may result in semiliquid friction, with sharp increase in the heat liberation and destruction of the working surfaces. Therefore, the minimum permissi� ble working gap [hmin] must exceed the critical value hcr by some value corresponding to working point 2 in the diagram; point 2 is to the right of point 1, which cor� responds to fmin. The permissible minimum working gap is assumed to be proportional to the critical value