On the Preliminary Design and Performance Prediction of Centrifugal Turbopumps—Part 1

A reduced order model for the preliminary design and performance prediction of radial turbopumps is illustrated. The model expresses the 3D, incompressible, inviscid, irrotational flow through helical blades with slow axial variations of their pitch and backsweep angles by superposing a 2D axial vorticity correction to a fully-guided forced-vortex flow with axisymmetric stagnation velocity in the meridional plane. Application of the relevant governing equations allows for the closed form definition of the impeller geometry and flowfield in terms of a reduced number of controlling parameters. Mass and momentum conservation are used for coupling the flow leaving the impeller with the 2D reduced order models of the flow in the diffuser and/or the volute, as well as for the evaluation of the mixing losses in the transfer between successive components of the machine. This information completes the geometric definition of the turbopump and determines its ideal noncavitating performance in accordance with the resulting flowfield. As a consequence of the neglect of viscous effects, the slip factor predicted by the present model exceeds those obtained from theoretical/ semi-empirical formulas reported in literature for centrifugal pumps, but correctly captures their trends.