Design and Investigations of a Three Dimensionally Twisted Diffuser for Centrifugal Compressors

For a 90-deg centrifugal compressor impeller with an extremely distorted exit flow distribution a vaned diffuser has been designed. The maximum flow angle difference across the diffuser width at the entrance is 29 deg. In order to match the vane inlet angle to this flow angle distribution the diffuser vanes are three dimensionally twisted. The map of the compressor with the twisted diffuser is compared with those using a commonly designed cambered vane diffuser and a straight channel diffuser. On the basis of detailed flow field measurements directly before and behind the diffuser and of the static pressure distribution along the diffuser, the performance of the twisted diffuser is discussed.