Numerical and experimental investigation to unsteady IGV-impeller-diffuser interaction

The unsteady IGV-impeller-diffuser interaction in a centrifugal compressor is investigated numerically and experimentally under at different IGV prewhirl angle; and the mechanism of unsteady IGV-impeller-diffuser interaction is explored. Results show that the maximum unsteadiness appears at the interface between impeller and vaned diffuser. When the IGV prewhirl occurs, the basic frequency of the unsteady flow in the vaneless diffuser is demonstrated as the blade passing frequency of the impeller or the half; when the stagger angle of the diffuser is increased, the basic frequency is dominated by the half of the blade passing frequency. The turbulence intensity and unsteady intensity increase toward the hub, and tend violently when IGV prewhirl angle of 60° matches with the diffuser stagger angle of 17°.