Centrifugal Compressor Map Prediction Based on Geometrical Parameters with Invariant Coefficients

In the present work, a new methodology for predicting the performance of centrifugal compressors is developed. The proposed method differs from existing methods found in literature by gathering principal losses in three parameters: two constants and one variable, which is a function of the compressor wheel geometrical characteristics. As those parameters are constants for a given centrifugal compressor, there is no need for additional corrective parameters in order to obtain coherent results. Indeed, the proposed methodology does not depend on the choice of the slip factor correlation for the prediction of the correct pressure ratio. However, the choice of slip factor influences the efficiency computation. The prediction of the compressor maps for two full stage centrifugal compressors is presented and they show good agreement while compared with manufacturer’s data obtained from gas stand measurements. In addition, a method to obtain the surge line based on this methodology is proposed and validated with good accuracy while compared with experimental and manufacturer’s data. A correction of the surge line parameter is proposed for ported shroud configurations. A final evaluation of the methodology using two well-documented Eckardt’s impellers with higher mass flow rates is presented showing a good prediction for back-sweep angle impellers and lower agreement with radial exit impellers.