Evaluation of shaft forces in a vertical canned motor through local hydraulic loss analysis

Abstract

In order to improve the stability and the lifespan of rotating components in a canned motor of a centrifugal pump, a local hydraulic loss analysis has been performed based on detailed flow field analysis by Reynolds-averaged Navier–Stokes–based re-normalization group k-ε turbulence model simulation. An energy balance equation was applied to analyze the local hydraulic loss distribution. The stator flow channel in the motor was modeled as a porous medium, by utilizing the Ergun equation. Due to the complex structure and the velocity gradient in the complicated flow field, a strong circulation flow exists in the thrust bearing outer ring. Moreover, circumferentially asymmetric Taylor vortices in the vicinity of the hydrodynamic bearing and unsymmetrical Taylor vortices in the transitional region after the thrust bearing were predicted. Dean vortices in the distributary pipes are also captured. These complex vortices are accompanied with high dissipations. A strong increase in hydraulic losses are observed in the corresponding canned motor parts (x/x max = (0.03, 0.23), (0.87, 1)). Moreover, a strong increase in the radial force and the axial force are predicted in the relative parts of canned motor ( x/x max = (0.84, 0.97), x/x max = (0.24, 0.17), (0.84, 0.97), respectively).