| Tilting tile dynamic pressure gas bearing is composed of multiple tiles.Because each tile can freely tilt and swing,it can self-adjust,so it has good stability.Tilting pad dynamic pressure gas bearing has been widely used in low temperature machinery and high speed rotating machinery because of its high speed,good stability,low energy consumption,small friction and other excellent properties.With the development trend of modern machinery miniaturization,the demand for bearing miniaturization is increasing day by day.Especially with the development of MEMS,micro machinery has ushered in a new era of development.As a key support component in MEMS,micro-gas bearing has also been greatly developed.The research on the static characteristics of gas bearing under small clearance becomes particularly important for the design and calculation of gas bearing.Based on this situation,this paper takes the micro tilting pad dynamic pressure gas bearing as the research object to analyze the performance of micro tilting pad dynamic pressure gas bearing under small clearance.In this paper,the general form of Reynolds equation in Cartesian coordinate system is derived firstly with the micro tilting pad dynamic pressure gas bearing as the research object.A simple derivation process of boundary slip velocity is introduced.Two slip models are used to derive the airflow velocity under the modified slip model.Based on this,the steady-state dimensionless static Reynolds equations for different models are derived.Considering the influence of slip effect,the Reynolds equation for tilting pad dynamic pressure gas bearing under slip effect is established by using the first-order slip and Wu’s new slip velocity correction term.The finite difference method combined with Newton iterative method was used to calculate the dimensionless gas film pressure,bearing capacity,friction coefficient and mass flow rate of the miniature tilting shoe dynamic pressure gas bearing under continuous model,first-order slip model and Wu’s new slip model.The calculation results of static performance under three models were compared and analyzed,and the rule changes of static performance under different models were summarized,which provided a reference for the design optimization of miniature tilting pad dynamic pressure gas bearing.Under different given parameters,the Reynolds equation is solved based on three different models.The results show that the bearing capacity of the miniature tilting pad dynamic pressure gas bearing is directly proportional to the compression coefficient and deviation ratio.The friction coefficient is positively proportional to the eccentricity,compression coefficient and preload coefficient.The mass flow rate and eccentricity are inversely proportional to the friction coefficient.The sliding velocity at the boundary decreases the bearing capacity,film pressure and friction coefficient,and increases the mass flow rate of the miniature tilting pad bearing.But the slip effect has little effect on the friction coefficient.With the increase of eccentricity,the effect of slip on bearing capacity increases.In terms of bearing capacity,film pressure and friction coefficient,the results of Wu’s new slip model are the smallest,followed by the first-order slip model and the continuous model.On the contrary,the mass flow of the continuous model is less than that of the two slip models.Based on the calculation results of three models,the influence of flow factor on the performance of micro tilting pad hydrodynamic gas bearing is analyzed.The results show that the friction coefficient and mass flow of the micro tilting pad hydrodynamic gas bearing are between the first order slip model and Wu’s new slip model.Considering the above,based on the fact that slip effect exists objectively,Wu’s new slip model is used to calculate the static performance characteristics of tilting pad hydrodynamic gas bearing with small clearance,and the data obtained is more accurate. |
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