Numerical Simulation On Performance Of Hydrostatic Turntable System's Oil Film

Heavy, large, high-speed, precision, automation, multi-function machine tools with large size, heavy, high precision properties is the trends of industries. It has higher requirements on its structure, the environment and control systems. The oil film's performance in fluid lubrication technology will directly affect the reliability of operation, life and economic indicators.A 3-D model of hydrostatic turntable was set up to simulate the flow of oil film. Laminar flow model and the finite volume method are selected in the simulation by using FLUENT software and CFD theory. Influences of viscosity, temperature– viscosity relationship, pressure - viscosity relationship, round oil chamber's geometry feature et al on oil film's performance were investigated. The difference between Newtonian fluid and non-Newtonian fluid was also compared. Results are in the following:(1) Influences of lubricant oil's viscosity on hydrostatic bearing capacity and stiffness of the system were studied. It can be obtained in the conditions of other factors being constant that carrying capacity and stiffness of hydrostatic bearing system are increased with the augment of oil viscosity, meanwhile, oil cavity temperature also increased.(2) Temperature's effect considering the temperature - viscosity characteristics on carrying capacity and stiffness of hydrostatic bearing system was calculated. It is shown that the temperature - viscosity characteristics has great influence on the oil chamber's carrying capacity, stiffness and temperature rise. It should not be ignored that the environmental temperature and the heat generated by friction's influence on oil's viscosity in the numerical simulation and engineering design.(3) Pressure's influence considering the pressure - viscosity characteristics on the carrying capacity and stiffness of hydrostatic bearing system was calculated. It is presented that the pressure - viscosity characteristics can change the oil chamber's carrying capacity and stiffness. Especially in overload and high-pressure conditions, the pressure - viscosity characteristics should not be ignored.(4) The geometric characteristics of the circular cavity's influence on the performance of hydrostatic bearing system were analyzed. It is found that the carrying capacity of the oil chamber can be increased by decreasing film thickness and the depth of the oil chamber, or increasing the width of oil chamber's oil seal edges and diameter of oil chamber. However, the turntable will have poor stability when the depth of the oil chamber is smaller. Therefore, carrying capacity, stiffness and stability should be taken into account in choosing the circular oil cavity's geometry. (5) The Newtonian fluid and non-Newtonian fluid's performance were compared under different speed conditions. It is given that, with the high shear rate conditions, the Newtonian fluid and non-Newtonian fluid have different behaviors. In addition, the oil with high viscosity or the characteristic of shear thickening has a good performance in the high-speed conditions.In the whole, Effects of temperature - viscosity and pressure - viscosity relationship are significant, and should not be ignored in hydrostatic support system's research and design. Capacity of oil chamber and the oil film stiffness could be increased by changing the geometry characteristics of the oil chamber so as to remove the lubricant selection limitations. Meanwhile, the rheological property should be considered to ensure the film's performance in choosing the oil. Results on the hydrostatic bearing system have important guiding significance on oil cavity geometry's design and the choice of lubricant oil.