APPLICATION OF NANOSTRUCTURED LAYER TO IMPROVE THE ENERGY EFFICIENCY IN HYDRAULIC PISTON PUMP

The mechanical power losses in a hydraulic pump come from the friction between parts in relative motion. The need to provide, especially at low rotational speed, hydrodynamic lift, causes power losses, in terms of volumetric and mechanical efficiency, due to the contrasting need to increase leakage to provide lubrication and to keep a minimum clearance in meatus to limit the volumetric losses. The application of special surface treatments have been exploited in pioneering works in the past, trying different surface finishing or adding ceramic or heterogeneous metallic layers. The potential of structured coatings at nanoscale, with superhydrophobic and oleophobic characteristics, has never been exploited. This paper shows the experimental results obtained using a nano-coating (developed by ISTEC-C.N.R.) to reduce the friction losses, in order to improve the overall efficiency map of an axial piston pump. This paper shows the functional performance of the nano-coated slippers surface using a dedicated test rig developed at IMAMOTER-C.N.R., able to ensure hydrostatic working condition during the mutual rotation between the slippers and the swash plate. A comparison between experimental results from the nano-coated and the not functionalized surfaces shows clearly that more than 30% of friction reduction can be achieved using the proposed nano-coating methodology.