The effect of oil pressure and temperature on barrel film thickness and barrel dynamics of an axial piston pump

Efficiency improvement in piston pumps and motors is a major task in pump development. Just a small improvement in efficiency can have a significant financial impact, particularly on large manufacturing plants employing many large-power pumps. According to the bibliography, effort has been concentrated in studding slipper swash plate leakage, forces, torques and slipper dynamics, but less attention has been given to the understanding the barrel dynamics and the inherent clearance between the barrel and the port plate. This paper clarifies the understanding of the complex barrel dynamics, pointing out how barrel-port plate film thickness depends on oil pressure and temperature. The paper demonstrates that mixed lubrication exist between the barrel face and the port plate under some of the conditions studied, proving that elastic metal to metal forces play an important role when studding barrel dynamics. According to the authors, more effort should be considered into properly designing the barrel sliding surface since both volumetric and mechanical efficiencies are very much dependent on this design. Fluid used hydraulic oil ISO 32.