Added mass moment of inertia of centrifugal dredge pump impellers

During the design of dredge pumps and drivelines, a torsional vibration analysis is performed in order to determine the critical frequencies of the system. The analysis requires information about the centrifugal pump impeller mass moment of inertia. For the impeller itself this geometrical property can be determined very accurately, but the influence of the surrounding fluid on the impeller's mass moment of inertia is much less easy to determine. This paper addresses the influence of fluid on the mass moment of inertia of a centrifugal dredge pump impeller, that is, the added mass moment of inertia. It describes the design of a test set-up for measuring the added mass moment of inertia of scale model impellers. Then a series of experiments is conducted in which the impeller geometry is varied. The parameters of influence are the impeller width ratio, the ratio between the suction diameter and impeller diameter, the number of blades and the blade shape. Analysis of the data provides insight into the importance of the added mass moment of inertia to the dynamics of the pump. Furthermore, the data provide a base for an engineering formula for the added mass moment of inertia of centrifugal pump impellers.