Design, Development and Testing of Water-Lubricated Ceramic Journal Bearing

Strong shear force developed in the fluid film as the water-lubricated hybrid bearing operates at high speeds. Thus the phenomena of shaft expanding outward and bearing contracting inward happened due to the increasing temperature of the fluid film caused by the friction heat. So the bearing clearance decreases on account of the thermal deformation of the shaft and the bearing. Seriously, there will be a risk of seizure accident when the speed gets higher. Friction heat may be weakened by adopting low viscosity lubricant and thermal deformation may be reduced by adopting low expansion coefficient materials. Such as the ceramic’s expansion coefficient is 3–5 times smaller than that of typical journal bearing material like tin bronze. Thus, a ceramic journal bearing was developed in this paper to weaken the thermal influence on the bearing clearance. For improving the temperature rise of the journal bearing, a water-lubricated ceramic hydrodynamic-hydrostatic hybrid bearing test rig was designed firstly. Considering expansion coefficient and thermal conductivity effects, the simulation method was used to study the variation of bearing clearance with the speed and the original bearing clearance. Then, the water-lubricated ceramic hydrodynamic-hydrostatic hybrid bearing test rig was developed to verify the temperature characteristics at different speeds. Results indicate that the relative error of the tested temperature results and simulation results was below 10% at different speeds. Lastly, the evolution of bearing clearance with speed and the original bearing clearance was studied through FEM. The advantages of ceramic material were more obvious with the increase of the rotation speed when exceeds 8000rpm.