| Porous aerostatic bearing has widely used in precision machinery,because of its small friction coefficient,large bearing capacity,simple structure,good rigidity and damping properties.Porous aerostatic bearing is an external air supply bearing and there are many tiny pores inside the porous material.When air pass through porous materials,porous aerostatic bearing can form a high pressure film on the surface to suspend the weight.Gas flow model of Porous aerostatic bearing is complicated,because the external supply pressure,the structure parameter of bearings,machining technology plays an important role in it;At present,the application of porous aerostatic bearing in low speed and heavy load is studied,but there are few studies about porous aerostatic bearing in high speed.Therefore,in this thesis,the static theoretical model of porous bearing is established,and the influence of different factors on bearing performance is explored;A high speed rotor system supported by tilting pad porous bearing is designed and its vibration characteristics are studied.The main studies of this paper are as follows:(1)Based on Darcy's law and mass conservation equation,a theoretical model of static gas flow in a porous hydrostatic thrust bearing is established,then the boundary conditions are given and the model is solved.The effects of porous materials with different permeability and thickness of porous materials on the static performance of bearing gas mass flow,bearing capacity and stiffness were investigated;the correctness of the theoretical model is verified by comparing the design experiment with the theory.(2)High speed rotor system supported by tilting pad porous static gas bearing is designed.Two rotor shafts are designed for the study of rigid and flexible shafts.After calculating the dynamic stiffness and damping coefficient of tilting pad porous bearing,the rotor dynamics of the designed rotor system is simulated with XLrotor,and the critical speed,stability and amplitude magnification factor of the system are analyzed in order to the design can meet the design requirements and the rotation performance is good.(3)Tilting pad porous hydrostatic bearings with curved surface radians of 60 °and 75 °was designed,then the rotor system performance was studied.The bearing with 60 °curved curve is not very effective on shaft suspension,and the bearing with 75 °curved curve has better suspension effect than the bearing with 60 °curved curve.The experimental results show that the amplitude of the rotor system is small,but there are many the high frequency in test. |
PDF Full Text Request