Design of a Test Setup for the Characterization of the Dynamic Transfer Matrix of Cavitating Inducers

Abstract

The paper describes a reduced-order analytical model for the characterization of the dynamic transfer matrix of complex test setups including cavitating pumps. The model, even if based on several simplifying assumptions (quasi 1-dimensional flow, small oscillations, incompressible working fluid, quasi-static response of all the components of the system), is able of providing good indications about the order of magnitude of the expected pressure and flow rate oscillations in the system under given flow conditions and, more in general, about the experiment design. The model has been applied to Alta’s Cavitating Pump Rotordynamic Test Facility with the custom-designed DAPAMITO3 axial inducer, in order to start the design process of an experiment for the characterization of the inducer dynamic matrix. It has been found that a good mechanism for providing an external excitation to the facility can be represented by a device able of mechanically vibrating the water tank in a vertical direction, while the most suitable way for obtaining the second linearly independent test configuration, needed for the experimental characterization of the cavitating pump dynamic matrix, is represented by a variation of the suction line inertance. Finally, it has been shown that it is possible to measure the flow rate oscillations in the suction and discharge lines by means of the difference between the measurements taken by two pressure transducers, placed at two different sections of the relevant pipe line.