A Generalised Mixed Flow Pump Model for Waterjets Simulation

Abstract: In the paper a generalized performance map for mixed flow pumps currently in use in waterjet propulsors is proposed. It is derived from the observation of a number of performance maps of typical waterjet pumps, and from fluid-dynamic and similitude principles of the hydraulic machines. The mixed flow pump map here proposed, showing constant speed and efficiency curves in the volumetric flow-head plan, is presented in non dimensional form, in order to generalize its application field to pumps characterized by very different dimensions and performance. The paper presents also a suitable technique aimed to take into consideration the cavitation effects in the evaluation of the pump performance, and therefore also of the waterjet performance. As application example, the proposed generalized pump performance map was employed in a simulation code developed for the dynamic performance evaluation of a gas turbine-waterjet propulsion system for a fast trimaran ferry, already presented in a previous paper. The calculation results of the simulations are compared with data provided by the waterjet manufacturer.