1. wiLh its geometry as designated in Fig. 3. This consists of an upstream ramp, or tapered portion, foll.awed by a flat section. In rigid thrust bearings the ramp portion is usually of the order of 70-807: of the total bearing arc 5. With CETR's the parameter b that denotes the fraction of pad angle occupied by the ramp is usually much smaller, of the order of 0.5 or less. Likewise the optimum ratio (hl/hZ) = hi, or the slope of the ramp, which in rigid pads is around 2.2, is in CFTB'S much higher. Figure 4 shows the shapes of the two-dimensional film thickness and pressure profile typical of compliant foil thrust bearing. The basket-like shape of the film thickness generates some ambiguity as to the value of hmin. We see from Fig. 4 that the absolute hmin. occurs at the sides of the pad, at r = R1, r = R2, and at the end of the pad, 8 = 6. These segments of hmin. occupy a vanishingly small part of the pad area, whereas most of rhe pad has a film thickness determined by the floor of the deflectcd surface of the flat portion. We thus arrive at the notion of a "nominal film thickness", hx, ai; shown in Fig. 2. 'This ! i ill bu the quantity that will figure in the subsequent evaluations of the performance of the bearing.
2. U 1 1812 8,065,390