PIV And Numerical Study On Flow Characteristics In Oil Cavity Of Hydrostatic Bearing Turntable

Due to using hydrostatic bearing technology, hydrostatic turntable system hasgood bearing performance, small friction, good seismic performance, long life andgood stability. It is increasingly applied to the modern machine tool and becomes thecore component. Bearing capacity and film stiffness of the oil cavity in the hydrostaticturntable directly affect the machining accuracy and stability of the CNC machinetools and need further research.Particle image velocimetry (PIV) experiments and numerical simulation（Computer fluid dynamics, CFD）are used to study the flow characteristics in the oilcavity of the hydrostatic turntable system of high-end CNC machine tools. The effectof the inlet Reynolds number, oil cavity geometry factors and turntable movementspeed on the flow characteristics, pressure distribution, carrying capacity and filmstiffness of the oil cavity is analyzed. It provides theoretical guidance for improvingmachining accuracy and stability of high-end CNC machine tools.The main works and results of this paper include:(1) The effects of the inlet Reynolds number on the flow field structures andbearing capacity of the oil cavity in static conditions is studying. According to theflow similarity criteria, a transparent experimental model is designed and processed.PIV experiments and CFD simulation are carried out to study the flow field structureand carrying capacity in the cavity as the inlet Reynolds number increases from0to2100. The results show that primary vortex, second vortex and third vortex exist in theflow field. The inlet Reynolds number has a significant effect on the vortex number,size and location. With the increases of the inlet Reynolds number, the vortex numberincreases from1to3, vortex size increases, the position of the vortex center movesoutward along the radial direction, the bearing capacity of the oil cavity increases.(2) The effects of the oil cavity geometry factors on the flow field structures andbearing capacity of the oil cavity in static conditions is studying. The flow fieldstructure and carrying capacity in the cavity are studied at different clearance heightand cavity depth by using PIV experiments and numerical simulations. Therelationship between clearance height, cavity depth and vortex size is analyzed andthe pressure and shear stress distribution on the bearing surface are also gained. Theresults show that clearance height and cavity depth have an important impact on theflow field structure. As clearance height increases, the vortex number and wall shear stress remain unchanged, but the vortex size increases, the pressure decreases. Ascavity depth increases, the vortex number decreases, vortex size increases, theposition of the vortex center moves outward along the radial direction, pressure andshear stress on the bearing surface keep constant.(3) The effects of the inlet Reynolds number, bearing surface velocity and oilcavity geometry factors on the flow field structures and bearing capacity of the oilcavity in dynamic conditions is studying. The flow field structure and pressuredistribution in the cavity are studied by using numerical simulations by changing theinlet Reynolds number, bearing surface velocity and oil cavity geometry factors.Theinfluence of different external factors on the bearing and stability performance of theoil cavity is obtained. The results show that the inlet Reynolds number and bearingsurface velocity have great effect on the flow field structure. Four three-dimensionalvortices and four flow sates exist in the cavity recess under dynamic conditions. Theoil cavity geometry factors have a great influence on the flow field structure andbearing capacity.