Study On Thermo-Hydrodynamic Lubrication Properties Of Marine Thrust Bearings

Overload is one of main reasons causing marine thrust bearing failure, which leads to temperature increase and fracture of lubricating oil film, and results in pad surface wear and failure of the thrust bearings. In order to improve lubricating performance of marine thrust bearings, thermo-hydrodynamic lubrication properties of marine thrust bearings was investigated theoretically.First, mathematical model of thermo-hydrodynamic lubrication for marine thrust bearing was established, including Reynolds equation, energy equation, film thickness equation and thermo-viscosity equation. Pressure and temperature conditions were discussed, and bearing parameters, load capacity and frictional torque were defined. Finite difference method to solve the mathematical model was introduced.Then, isothermal properties of thrust bearings with plane-shaped pads were numerically analyzed. Numerical results illustrated that both load capacity and frictional torque decreases quickly with increasing oil film thickness. Increasing pad inclining angle leads to significant increase of load capacity but obvious decrease of frictional torque. While, load capacity as well as frictional torque increases greatly with increase of rotational speed.Further, investigation of thermo-hydrodynamic lubrication performance of thrust bearings was carried out with consideration of thermo-viscosity effect. Influence of film thickness, pad inclining angle and rotational speed on temperature distribution and pressure distribution as well as load capacity and frictional torque was numerically analyzed. Numerical results showed that oil film temperature increases gradually in the shear direction and reaches peak value at about outlet, which leads to decrease of bearing load capacity. General trend is that smaller film thickness, littler pad inclining angle and higher rotational speed produce a higher increase of film temperature, while load capacity is increased obviously at smaller thickness, higher rotational speed and larger pad inclining angle.Finally, influence of pad shapes was numerically analyzed in order to improve bearing thermo-hydrodynamic lubrication performance. Oil film pressure and temperature distributions were obtained for six different kind of pad shapes including plane shape, cylinder shape, transverse bend shape, anti-transverse bend shape, spherical shape and saddle shape. Influence of film thickness, pad inclining angle and rotational speed on maximum film temperature and load capacity was numerically analyzed. Numerical results show that pad face shape has a significant influence on load capacity and film temperature. Compared to the plane shape, the cylinder shape presents better lubricating performance with smaller temperature increase and larger load capacity, while the transverse bend shape leads to worse lubricating performance with larger temperature increase and lower load capacity.Based on analysis of thermo-hydrodynamic lubrication properties of thrust bearings, method of pad shapes was presented. The research work was helpful in perfecting design for engineering applications of the marine thrust bearing.