Research On The Elastohydrodynamic Lubrication Mechanism And Characteristics Of The Gas Foil Beraing With Texture Surface

The hydrodynamic gas foil bearing is widely studied because of its many outstanding advantages such as low friction,high adaptivity,pol ution free,high precision turning,long operating life,shock resistance and high stability.It is especially suitable for the machinery with high speed and light load.So it has a broad prospect of development and application in the key field.But there are many disadvantages in the hydrodynamic gas foil beraing.The friction exsiting between the foil and journal in the starting procedure of the foil bearing will make the foil structure be easy to wear and damage before the takeoff of the rotor.The surface texture technology provides a new way to improve the stiffness and load capacity of the foil bearing,decrease the wear of the foil and increase the damping of the system.However,there are many scientific problems needing to solve to apply the surface texture technology to gas foil bearing such as the undefined machanism of the surface texture in improving the tribological properties,the difference between the flow characteristics in the surface texture and the large scale flow characteristics in the bearing.To solve these problems,this dissertation uses the generalized Renolds equation based on the linearized Boltzman equation as the pressure control equation and estabilish the analytic model of surface texture gas foil bearing.First,this dissertation solves the static-state generalized Renolds equation with the Newton-Raphson iteration and finite difference method to abtain the caculation method of the surface texture gas foil bearing static characteristic.Then,solve the generalized Renolds equation with the perturbation method and finite difference method to get the caculation method of dynamic characteristics.All of this lays the theoretical foundation of the full text.Under the condition of rigid surface and flexble surface,the dissertation discusses the influence of surface texture by analyzing the dimensionless gas film pressure distribution and the dimensionless gas film thickness distribution..Then analyze the influence of surface texture on static characteristics under different rotate speed,number of surface textuer,depth of surface texture and eccentricity ratio.On the base of static characteristics,analyze the influence of the surface texture on the dynamic characteristics in the different four parameters by studying the whirl frequency.The results shows that the surface texture can improve the static and dynamic characteristic of gas bearing with rigid surface or flexble surface under certain parameters conditions.This dissertation applies the gas foil bearing with surface texture to the turbopump rotor system.According to the reaction force,it caculates the dynamic coefficients of the bearing.Then the finite element model of texture surface bearing-rotor system is established to analyze the critical speed and the unbalance response.The results show that the turbopump rotor needs to go through two critical speeds before reaches the working speed and there are no critical speeds near the working speed.The unbalance response amplitude of the turbopump rotor system is small.This dissertation makes a preliminary study on the application of the surface texture technology in hydrodynamic gas foil bearing.