Improving the operating range using a centrifugal compressor with a tandem impeller

The centrifugal compressor is being utilized in both commercial and military applications; however, the compressor performance is limited by flow instability affecting the stable operating range. In this paper, a tandem-bladed impeller method is employed to achieve passive flow control to improve the stable operating range of a compressor without control costs or performance penalties. The results inspiringly indicate that the tandem impeller method can achieve a maximum operating range gain of 16.7%. The baseline compressor instability is induced by tip region flow deterioration, which results from tip leakage flow and low-momentum fluid radial transport. For a tandem impeller, the inducer suction side always has a higher trailing edge static pressure compared to the baseline impeller due to the exducer potential influence and the restriction of the Kutta-Joukowski condition, which weakens the radial transport of low-momentum fluid and constrains the leading-edge separation. As a result, the tandem-design compressor operates far from the impeller instability point. Further investigations show that the inducer pressure field varies with the clocking fraction lambda(s), which results in the change of the radial transport at the inducer suction side, finally affecting the flow stability. (C) 2019 Elsevier Masson SAS. All rights reserved.