Simulation Study On The Effect Of Gas Molecular Interface Sliding On The Bearing Capacity And Sealing Characteristics Of Micro Bearings

In micro scale gas lubrication,the gas molecular interface slip effect will obviously change the pressure distribution along the gas flow direction and the velocity distribution along the gas film thickness direction on the micro scale,thus affecting the change of physical quantities such as the gas film bearing capacity and flow rate on the macro scale.With the development of gas bearing microminiaturization,the K nudsen number of lubricating gas film begins to enter the transition region.The traditional first-order slip and second-order slip boundary conditions with fixed slip coefficient can not accurately describe the gas flow in this case.In order to further study the effec t of gas molecular interface sliding on the bearing capacity and sealing characteristics of micro bearing,a new boundary condition of sliding is introduced to modify the flow control equation,which is suitable for any Knudsen number.The numerical simulation of the static characteristics of gas film is carried out for the step plate,plane spiral groove and its derivative model.The accuracy of the numerical method is verified by comparing with the numerical results of previous scholars.By comparing the calculation results under different slip boundary conditions,the results show that the boundary conditions such as the first-order slip after the gas film Knudsen number enters the transition zone obviously overestimate the gas film pressure value and the transport capacity of the gas medium compared with the new slip.As the gas film K nudsen number continues to increase,the relative deviation between the parameters further increases.When the step plate model reaches the maximum bearing capacity under the new sliding boundary under the same environment Knudsen number,it needs to provide greater moving speed compared with the first-order sliding.The deviation of bearing capacity between different sliding boundaries in the spiral groove model decreases with the increase of bearing speed.On the basis of the traditional plane spiral groove structure,the space spiral surface is filled with the spiral groove area,and a new type of gas bearing with variable height inclined groove of composite spiral boundary is obtained.Compared with the traditional bearing structure,the bearing capacity of the new bearing structure calculated at a relatively low bearing speed is significantly improved.