Experimental study on hydrodynamic performances of naval propellers to adopt new additive manufacturing processes

In the past few years, a new generation of additive manufacturing (AM) techniques has rapidly become available due to the expiration of some AM patents which allowed significant cost reductions. This article explores some available techniques fostering products innovation in experimental laboratories for the development of naval propulsion, where high costs represent an important limitation for both basic research and industrial testing, by identifying significant knowledge and variables and by providing reliable and accurate data to support designers and researchers. The propeller INSEAN E779a case study was taken into account and fabricated by direct metal laser sintering in AlSi10Mg aluminium alloy and by fused deposition modeling in acrylonitrile-butadiene-styrene, and UltraT polymeric materials. The study of printing parameters, flexural tests, differential scanning calorimetry and thermogravimetric analysis, allowed to optimize the printing process conditions. A reverse engineering system, Faro-CAM2, and the iterative closest point algorithm of the geomagic control software were used to analyse deviations from the printed propeller and the CAD nominal model. The atomic force microscopy test allowed to assess the morphological features and surface roughness of printed propellers. Towing Tank tests were carried out and the hydrodynamic performance comparison was analysed in terms of torque and drag. The results of this study show differences between the benchmark and AM propellers, as a function of the advance coefficient J, the morphological characteristics and the materials. However this study also shows a substantial adequacy of AM propellers in most studies carried out in Towing Tank.