Numerical analysis of slipper bearing's film shape in axial piston pump using genetic algorithms

The film shape of slipper bearing has a great influence on its lubrication characteristics in axial piston pumps. In order to calculate the slipper lubrication characteristics correctly, the film shape should be obtained precisely. Firstly, considering the slipper overturn phenomenon, the film shape was described by using non-uniform gap, and the lubrication equation of the slipper was established and solved by the Gauss-Seidel relaxation method to obtain its pressure field. Then an optimization problem, which consists of two decision variables, one objective function, two equality constraints and two inequality constrains, was deduced for the film shape. The two equality constraints are based on the simplified normal force balance equation and flow rate continuity equation, which were obtained with equilibrium analysis of force on the slipper by considering the relation between the film shape and a corresponding pressure field. The two inequality constrains, the slipper tilt angle and azimuth angle were involved. Finally, the Niche Genetic Algorithm was applied to solve this problem. The results showed that this method is really robust and can achieve the optimum solution faster with a higher accuracy, and can get a steady 3D film shape of a slipper precisely. The method has provided a theoretical base for correct prediction of slipper lubrication characteristic and slipper bearing design.