Running Performance of a Squeeze Film Air Bearing with Flexure Pivot Tilting Pad

Abstract

A novel flexure pivot tilting pad squeeze film air bearing (FPTP-SFAB) based on near-field acoustic levitation (NFAL) for a rotor is proposed in this article. The most important advantage of this structure is the suitability of the bearing for high-speed and light load conditions because the FPTP can adapt well to squeeze action during operation. The rotating orbit of the rotor can be adjusted according to the machining conditions. A theoretical model is employed to analyze the running characteristics of the rotor by using the coupled NFAL and FPTP model. Experiments were conducted to investigate the running performance of the rotor–bearing system. Moreover, the effects of input voltage, rotational speed, eccentricity ratio, radial clearance, vibration amplitude, and installation method on bearing performance were analyzed. Numerical and experimental results show that a rotor supported by the FPTP-SFAB with a reasonable input excitation magnitude can effectively adjust the rotating orbit of the rotor and inhibit the divergence of the rotor vibration amplitude, thus improving the stability of the rotor–bearing system under complicated and alternating machining conditions.

Keywords:

• Squeeze film lubrication
• near-field acoustic levitation
• gas journal bearing
• rotor–bearing system

Appendix

The mode shape of the bearing for one pad is illustrated in Fig. A.1, which are dimensionless results. The input voltage (peak-to-peak value) and resonant frequency are 200 V and 49.1 kHz, respectively. The position of the test location measured along the pad is indicated in Fig. 3. Nodes 1 and 2 are on the test line but have different positions (nodes 1 and 2 are at the midpoint and at the end of the test line, respectively). Hollow pentagons represent calculation results from finite element analysis (FEA), red marks indicate experimental data, and the solid line represents a fitted curve based on the FEA results. Figure A.1 clearly shows that the mode shape is symmetrically distributed along the circumferential direction, and the maximum value is obtained at both ends of the pad. Study results show good agreement between the actual measured value and the FEA results.

Figure A.1. Mode shape of the bearing for one pad.

Additional information

Funding

This work was supported by the National Key R&D Program of China (2018YFB2000100), the National Natural Science Foundation of China (51875185, 51705140), and the Foundation of Hunan Province (2018JJ1006).