Research On Modeling Method Of Two-phase Flow Field And Rotor System Of Sliding Bearing Based On Fluent

Sliding bearing has been widely used in industry because of its good performance of vibration absorption,noise reduction and high reliability.In the actual operation environment,the bearings are sometimes in the lubrication of non pure oil because of the poor sealing or insufficient oil supply.Whether the bubbles are mixed with oil from outside or the cavitation produced by cavitation effect,the sliding bearings are in the dynamic lubrication state of the oil-gas two-phase flow.The dynamic characteristics of oil film flow field can be changed by bubble diffusion movement and generation of cavitation,even those affect the stability of the rotor system further,eventually lead to collision and friction failure.The lubrication of oil-gas two-phase flow in sliding bearings is studied as flow.The relation between external factors and motion of air phase is analyzed,and then the influence of air phase change on the dynamic properties of bearing oil film flow field is summarized.Not only the characteristics of the stability of the sliding bearing in two-phase lubrication are supplemented,but also a possible option for troubleshooting.At present,the domestic oil and gas lubrication research is relatively less,therefore establish a dynamic model of sliding bearing oil-gas two-phase flow under a specific condition is of great significance.Firstly,the theory of hydrodynamic lubrication,the principle of cavitation and the theory of bubble dynamics are introduced.The Reynolds equation is derived according to the simplified conditions.An oil film observation system for simulating sliding bearings having a bubble in flow filed is designed and constructed.The image of bubbles and cavitation in the oil film flow field is recorded by high-speed camera,and the law is analyzed.The results show the effectiveness of the simulation made in Fluent.The oil film flow field model of oil gas two-phase flow was established in Fluent,effects on the bubble shape and flow capacity coursed by the bubble volume,bubble location,bearing width diameter ratio,rotational speed and eccentricity is analyzed;The effects of cavitation pressure,medium viscosity,aspect ratio,rotating speed and eccentricity on cavitation and bearing capacity of flow field are analyzed.The difference between two kinds of two-phase flow and pure oil flow field model is compared.The simulation results show that the average bearing capacity of the oil film with bubbles is lower than that of pure oil,and the bearing capacity of the oil film with cavitation is also lower than that of the pure oil,but higher than that of the half cycle oil film.When the bubbles enter the positive pressure zone of the bearing,the bearing capacity decreases,and the bearing capacity increases when leaving the negative pressure zone.The influence of the wall speed on the oil film flow field is analyzed,the flow field speed is added to the outer surface of the oil film,and a rotor dynamics model is established to solve the dynamic oil film flow field.Through the UDF custom program and the dynamic mesh model,the influence of the bubble and cavitation on the trajectory of the axle center is calculated.When the cavitation occurs,the oil film bearing capacity appears transient disturbance,and then stabilizes,and the oil film bearing capacity value is equal to the gravity value.The model has the advantages of simple setting and fast calculation.