Numerical studies on application of blended blade and endwall technique on transonic centrifugal compressor

With the continuous improvement of pressure ratio and efficiency in centrifugal compressors, the aerodynamic load is increased significantly. Some unnoticed tiny structures are found having notable influence on centrifugal compressor performance, for example, corners profile between the end walls and the blades. Aiming at this problem, the present paper mainly focuses on the applicability of Blended Blade and EndWall (BBEW) design on the transonic centrifugal compressor. Firstly the Krain transonic impeller is chosen and the predicted flow field is compared with detailed measurement data using commercial CFD code Numeca. The results show that the overall performances are consistent and the details of flow fields are captured accurately. Then a series of uniform value fillets along streamwise are implemented to the hub of transonic centrifugal impeller. The numerical tests show that the aerodynamic performance is deteriorated with the augment of fillets radius, but it seems that adding fillet to the hub of splitter blade can brought positive and negative returns at the same time. Next, as a preliminary original work, a kind of simple Blended Blade and EndWall (BBEW) design which adapt variable radius distribution fillets along streamwise are implemented to the hub of the impeller. Through designing different configurations, the authors find that the performances of some impellers designed by BBEW can be not only higher than impellers with uniform value fillets, but higher than original impeller slightly. In addition, some results are presented on the comparison of flow field structures in different impellers.