Internal recirculation channel application in centrifugal compressors

Centrifugal compressors with high pressure ratio used in gas turbines often have a small range of stable operation region, which has a negative impact on their operation. One of the contemporary arrangements aiming to extend its stable operation regimes is to use specially shaped air flow by-pass channels (Internal Re-Circulation (IRC) systems) located at the compressor inlet. The paper is focused on the evaluation of different shapes of the IRC in terms of air flow and losses in these channels, including the velocity distribution in front of the inducer. Evaluation is based on the results of experiments with IRC physical models and calculations in CFD programs.