Impeller Blade Unsteady Aerodynamic Response to Vaned Diffuser Potential Fields

Abstract

To predict the unsteady aerodynamic response of centrifugal compressor impeller blades to the potential field generated by the downstream vaned diffuser, a small perturbation model is developed that considers the number of impeller blades and diffuser vanes, the impeller blade backsweep angle, the impeller rotational speed, and the mass flow rate. The unsteady flow is analyzed in the impeller exit region and the vaneless diffuser space between the impeller and the diffuser leading edge radius, where the unsteady flow generated by the diffuser vane potential field is most significant. The unsteady flow perturbations are superimposed on an irrotational two-dimensional steady flow model, resulting in an analysis that is consistent with the small perturbation velocity potential equation. This model is then applied to a representative modern high speed impeller-vaned diffuser configuration.