Performance of novel air foil thrust bearings with taper-groove on surface of top foil

Abstract

To improve the load capacity of air foil thrust bearing, the micro taper-grooves on the surface of top foil was introduced and studied. A modified Reynolds equation considering the gas rarefaction effect was established, in which the Knudsen number was affected by the film thickness and pressure. A new bump stiffness model was built with the consideration of bump rounding, friction, and bending stiffness of foil. By considering the variation of gas film thickness, the load capacity, friction torque, and power loss of novel bearing with grooves were calculated by the finite difference method. Moreover, the effect law of groove parameters, groove shape and grooves number on the novel bearing performance was studied systematically. The results show that the predicted axial load capacity considering gas rarefaction effect is decreased slightly in smaller clearance and more consistent with the actual test data. The novel air foil thrust bearing with taper-groove can weaken the air end leakage and enhance the local dynamic pressure efficiently in the parallel portion of top foil, thus improving the static characteristics of bearing. For the novel air foil thrust bearing with taper-groove depth of 10 µm, the load capacity can be increased by about 13.33%, compared with traditional bearing. With the increments of taper-groove depth and length on top foil, the load capacity can be increased. However, the friction torque is decreased when there is a longer taper-groove in the circumferential direction. Meanwhile, the optimal groove width ratio is about 0.5, and the structure of multi-grooves is beneficial to the decreased friction torque. The validity of presented theoretical model has been verified by the literature data, and the results are expected to be helpful to bearing designers, researchers, and academicians concerned.