An Experimental Study of Cavitation Erosion in a Propeller Fabricated Using Additive Manufacturing
Abstract
Cavitation on marine propellers has several adverse effects, including altered performance, loss of flow stability, increase in noise and material damage/erosion [1]. The latter is caused by repeated pitting of surfaces of propellers and hydraulic machines by collapsing bubbles, resulting in loss of material, altered shape, and eventual failure. Considerable effort has already been invested in understanding of resistance of different materials to cavitation erosion, with general consensus that the damage decrease with increasing material hardness. However, the recent rapid increase in applications of additive manufacturing (AM), the process involving use of data to deposit material, layer upon layer, to produce complex objects, raises questions on the resistance of these layered materials to cavitation erosion. This proposal focuses on cavitation erosion of a propeller manufactured using AM, followed by precision CNC machining to obtain the final geometry. It extends the scope a multi-institution project aimed at characterizing and modeling cavitation inception as well as the 3D flow and pressure field around a propeller, taking advantage of recent advances in flow measurement techniques. The ongoing experiments involve two acrylic propellers installed in a refractive index matched facility, to obtain an unobstructed optical access to the flow field, and an AM manufactured propeller made of 6061aluminum with an identical geometry, to test its response to high unsteady loading and its impact on cavitation inception. The proposed destructive tests will followthe initial experiments, which are not expected to involve erosion. To test the cavitation erosion of this propeller, it will be exposed to extensive cavitation, at cavitation indices well below the inception level, for prolonged periods. Erosion or material lossrates on the surfaces will be monitored and documented as a function of time and intensity of the cavitation events at different locations on the propeller surface. Since the resistance of the layered material to erosion is expected to vary with the alignment of layers relative to that of the surfaces exposed to cavitation, different parts of the 3D propeller could possibly have different sensitivities to cavitation erosion. Consequently, the erosion rates in the tip region will be documented separately from those occurring on the blade suction side, with particular attention being paid to effects of interface between layers on the material loss. Combined with the experiments characterizing the unsteady 3D flow and extent of cavitation around this propeller, the records of erosionwill provide unique record of the effect of flow mechanisms ad extent of cavitation on the erosion of AM based propellers. Approvedfor public release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 08, 2024
- Source ID
- N000142412408
Entities
People
- Joseph Katz
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy