| Foil bearing supported by elastic surface is one self-acting hydrodynamical bearing. Comapred with traditional rigid surface gas bearing, the structure of foil bearing is more complexiable. However, being the foil's elastic feature, foil bearing has many outstanding advantages such as self-adaptive ability, high speed, withstand high tempature, lower friction loss and well rotating stability, et al. Foil bearing has important valuable application and vast potential for future development in those fields including cryogenics, refrigeration, avigation, aerospce engineering and defence-related science and technology, in developed countries( such as American), foil bearing has been successfully applied in F-16, F-18, B-1B, B-2, SAAB-2000 and boeing 777, et al. In past several decades, lubrication of foil bearing is mainly focused on air or gas, liquid-oxygen or liquid-nitrogen, and so foil properties, foil manufacturing and processing and foil surface coating become the critical problems. And also these critical technologies hinder the foil bearing development and application. According to above reasons, oil lubricated foil bearing was firstly presented in order to decrease the difficulties of material, manufacturing processing and coating. In theoritical analysis, the characteristics of oil lubricated foil beaing studied are compared with that of air/gas lubricated foil bearing. In the end, the special oil lubricated multileaf foil bearing-rotor system test-bed is designed and established, and a series of experiments have been done.Based on air film chickness model, Finite Deference Method (FDM) and Newton-Raphson iterative Method are both applied to solve the coupled air film thickness and the Reynolds pressure govening equation. The solution programm is verified by the published data of experiment and relevant reference. The distribution rules of air film thickness and pressure are compared between foil bearing and triditonal rigid bearing, it indicates that air foil bearing has higher load carrying capacity and stability than rigid bearing. And more, the static characteristics of both air lubricated bump foil bearing and multileaf foil bearing are discussed including the influence of bearing number Ax, eccentricity and L/D on static performance, the relation between bearing number Ax and friction torque, the distribution features of air film thickness and pressure. The influences of foil compliant number and foil predeformation on static performance are specially studied, it shows that it is effective to improve the load capacity and stability by the way of increase foil predeformation. According to the condition of half-Sommerfeld, oil film thickness model is build and coupled with the oil pressure Reynolds equation. The static characteristics of oil lubricated bump foil bearing and multileaf foil bearing are analyized, and contrsted with that of air foil bearings. More over, the influence of inlet oil pressure on performance is also studied. It indicates that oil lubricated foil bearing has higher load capacity and stability, and the inlet oil pressure can influence the static performance of foil bearing in a way.Based on small perturbation method, the film thickness, pressure and foil deformation displacement are expanded as Taylor series in terms of a small displacement and a small velocity at the equilibrium position, five equations which are related to the diferential pressure and film thickness are achieved. In terms of the balance relation among pressure, foil deformation and film thickness, another five diferential equations are built. The 8 stiffness and damping coefficients can be solved by coupling above 10 equations. The hydrodynamical stiffness and damping coefficients of oil lubricated foil bearing are firstly analyzed and compared with corresponding air lubricated foil bearing. The influence factors on hydrodynamical coefficients include eccentricity, bearing number Ax, L/D and foil deformation, even more, the influence of inlet oil pressure is also discussed. The results show that oil lubricated foil bearing can provide a more higher stiffness coefficients than that of air lubricated ones. And the higher inlet oil pressure also can improve the load capacity of foil bearing. In sum, the thought of oil lubricated foil bearing is possible for improving the performance of load and stability.The practical rotor-bearing system model is built and the elements and nodes are ploted respectively. The stiffness coefficients of oil multileaf foil bearing coming from the last perturbation method solution are substituted into the frequency equation achieved by Finite Element Method(FEM), and the values of theoritical critical speeds are solved. The Newmark method are used to analyzed the hydrodynamics of rotor-bearing system. It shows that the unbalance mass of both thrust plate and turbine will influence the rotating stability greatly, and that the vibration amplitude is greater in nondrive end than that of drive end, howerve, it is contrary when high speed. Oil lubricated multileaf foil bearing has good rotating stability at high speed.A special multileaf foil bearing-rotor system test-bed is designed and built, including oil lubrication system, driven turbine system, rotor, foil and bearing design, et al. Tests include critical speed experiment, speedup and coastdown both in low speed and high speed ranges, the influence of different radial clearance on rotating stability. The higherst rotating speed achived is more than 100kr/min. The experimental results proved that the idea of oil lubricated multileaf foil bearing can greatly decrease the requirements of foil features, foil manufacturing process and foil coating technology. Otherwise, oil lubricated multileaf foil bearing can also realize high speed with the common foil material of beryllium bronze, and has the well start-stop performance, the adaptive ability of speedup and coastdown, the ability of against impact and vibration. Being the lower foil surface friction and abrasion, it is more effective to prolong the foil operation life.
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