Shrouded centrifugal pumps are widely used in industrial applications such as process machines, and they can suffer from rotordynamic instability. Eccentric shrouded impellers induce non-axisymmetric flow fields which, in turn, lead to rotordynamic forces. Therefore, a new analytical flow model for shrouded pump impellers (which considers non-axisymmetric flow fields in the upstream inlet duct, shrouded impeller, and downstream) has been developed using an actuator disk approach. The model can predict impeller rotordynamic stiffness values from pump geometry and operating conditions. When compared to the available pump test data [1], the new model’s predicted stiffness coefficients agree well with the measured data. The new model’s predictions show the strong influence of the non-axisymmetric shroud inlet flow on the rotordynamic stiffness forces. The shroud inlet flow non-axisymmetry, in turn, results from the non-axisymmetric flows upstream of and inside the impeller blade passage induced by impeller eccentricity.

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