The Influence on the Meridional Impeller Shape on the Energy-Transfer in Centrifugal Compressors Free

Three radial flow impellers were tested having an elliptic blade shape and identical blade geometry at inlet and exit but different shapes of the meridional contours. The compressor maps with pressure ratios up to 2.9:1 are compared using time-dependent measurements of the static pressure at the shroud and of the flow angles closely downstream of the impeller. From these measurements, the influence of impeller shap on the jet-and-wake flow is discussed. It is shown that with increasing impeller length, the wake zone at the suction side of the blades can be only partially influenced and friction losses become dominant with respect to compressor performance. A smooth curvature of the meridional cross section of the impeller channel leads to a better jet-wake ratio at impeller exit. Accordingly, the performance characteristic shows higher values especially when the mass flow is increased.