An Integrated Finite Element and adams Modeling Approach for Analyzing Rotor-Bearing Housing Systems

Abstract

This article introduces a new modeling approach aimed at examining how the performance of a rotor-bearing housing system is influenced by the flexibility of the rotor and support structures. The system is composed of a flexible rotor and rolling element bearings (REBs) positioned within flexible housings. The dynamics of the REBs were simulated using a previously developed adams dynamic bearing model (DBM) using the discrete element method (DEM) in the msc adams environment. To achieve an integrated rotor-bearing housing system model, the adams bearing model was coupled through a set of interface points using component mode synthesis (CMS) for the rotor and housing model. The bearing outer races were discretized into multiple nodes to compute the force and deformation at the bearing housing conformal contact as well as to minimize the computational requirements associated with the conformal contact problems. The integrated model was then utilized to investigate the effects of rotor flexibility in the bearing rotor system and the effect of bearing clearance and housing clearance on bearing dynamics. Previously developed Pressure Mapping Test Rig (PMTR) and Spherical Roller Bearing Test Rig (SRBTR) were used to validate the results and assumptions made in this study. The model developed demonstrated that the flexibility of the rotor has a significant effect on bearing element motion and dynamics. The results also indicate that depending on the bearing type, the shaft deflection can induce a moment within the bearing that is not readily available from elementary theory. The results show that the flexible housing undergoes deformations that create ovality in the bearing housing, thus affecting bearing dynamics. The model was also used to investigate bearing performance in a miniature wind turbine main shaft, utilizing a combination of spherical roller bearing (SRB) and cylindrical roller bearing (CRB) adams models. Results suggest that the axial-to-radial load ratio should be less than the tangent of the SRB contact angle to avoid premature failure due to rollers sliding in the SRB as well as detrimental parallel misalignment in the CRB.