Analysis Of Oil-air Lubrication Two-phase Flow And Thermal Characteristics Inside High Speed Rolling Bearing

Rolling bearings are the primary support of high-speed motorized spindles,oil-air lubrication is the main lubrication method of high-speed rolling bearing,effective lubrication is the fundamental guarantee for the stable running of motorized spindle and its bearing.Oilair convection heat transfer is the main heat dissipation way of bearing,it directly affects the transformation of bearing temperature;the distribution of oil-air two-phase flow in bearing cavity is related to the lubrication state of bearing.The oil-air two-phase flow forms lubricating oil film in the bearing cavity,it affects the bearing capacity to support external load and lifetime.Therefore,it is of great significance to study the distribution of oil-air two-phase flow in the bearing cavity,the convection heat transfer of oil-air,the temperature field and the motion characteristics of oil film.Based on elastohydrodynamic lubrication,bearing dynamics and computational fluid dynamics,the fluid calculation model of rolling bearing is establish,a transient numerical calculation of the two phase flow distribution,convection heat transfer and temperature of the bearing cavity are conducted,the results of numerical analysis are verified by relevant experimental.The flow velocity and the state of oil film is calculated,the influence of working conditions on the film state and the film flow velocity is analyzed.The main conclusions of this paper are as follows:(1)Oil supply,air supply pressure and rotating speed are the main factors affecting the distribution of oil-air in the bearing chamber,the oil volume fraction first increases and then decreases with the increase of oil supply and rotating speed,the increase of gas supply pressure is beneficial to the distribution of oil phase.The flow velocity of oil-air,temperature difference between oil-air and bearing cavity wall surface are important factors affecting convection heat transfer,the convection heat transfer coefficient of oil-air first increases by 18.3% and then decreases by 10.1% with the increase of oil supply,appropriate amount of lubrication oil is conducive to heat absorption of wall surface.The increase of air supply pressure and rotating speed directly accelerates the flow of oil-air,thus enhance the convection heat transfer of oilair.(2)The temperature of the bearing inner ring is higher than that of the outer ring,and the temperature in the contact area is higher than that in the non-contact area,the temperature near the oil-air inlet is low.Lubrication oil is beneficial to heat dissipation and lubrication of bearing chamber,moderate increase in oil supply can reduce the bearing temperature rise.The air supply pressure directly affects the convection heat transfer of oil-air,when the air supply pressure is between 0.2Mpa and 0.45 Mpa,increase of air supply pressure can continuously reduce the temperature rise of bearing chamber.Heat production is a higher order function of rotational speed,the larger the speed,the higher the temperature rise of the bearing.Appropriately increasing the amount of oil and air imports will reduce the temperature rise by 22.5% and make the distribution more uniform the change of axial load directly affects the spin heat of the rolling body and then changes the temperature rise of the bearing.(3)The air supply pressure is related to the velocity of oil-air two-phase flow and the air flow rate,the increase of air supply pressure is beneficial to the formation of oil film.The oil film thickness first increases and then reduces with the rise of oil supply,excessive lubricating oil will increase the temperature of the bearing chamber and affect the oil film,effect of oil supply on oil film state is basically similar to that of rotating speed.The velocity of oil film is mainly affected by its own gravity and air shear force,the increase of oil supply,an increase of air pressure and rotation speed leads to the increase of oil film with air interface shear force,air supply pressure,oil supply and rotation speed will let the oil film velocity increase.