Influence of surface waviness in the heat generation and thermal expansion of the touchdown bearing

Abstract

In an active magnetic bearings (AMBs) supported rotor system, the touchdown bearings have been proposed to support the rotor during an electromagnetic field shortage. The heat generation due to the high impact and collision of the rotor and touchdown bearing, in addition to the internal friction in the bearing, raises the temperature of the touchdown bearing. In this work, a numerical model is applied to simulate the rotor dropdown where the FE-model of the rotor is integrated with the dynamic and thermal model of the touchdown bearing. The rotor that is used as a case study is supported by a deep groove ball bearing and a pair of angular contact ball bearings installed in an X-configuration. The present study focuses on evaluating different orders of surface waviness in a pair of angular contact ball bearings. The equivalent electrical circuit model is implemented for computing the thermal behavior of the touchdown bearing. Results indicated that the dynamic friction coefficient between the rotor and inner race has a considerable impact on bounce height and the whirling motion of the rotor. Furthermore, for a certain amplitude of surface waviness, the effect of various orders of waviness is investigated and it has been found that surface waviness of the bearing alters the contact force and friction loss in the touchdown bearing. In addition, the effect of a higher amplitude of surface waviness on thermal expansion of the touchdown bearing is studied.