Steady air injection flow control for increasing the surge margin of radial flow compressor

Steady air injection upstream of the leading edge was used to increase the surge margin of a centrifugal compressor. To reveal the mechanism, steady numerical simulations were performed on a high pressure ratio centrifugal compressor rotor operated with a rotor tip speed of 586 m/s. Eight different injection yaw angle with four different injection mass flow was performed to determine the configuration that provide the best results for the compression system studied in this work. The injection angle, α, was fifteen degree and the injectors were placed at short distance (ten percent of the inlet tip radius upstream of the compressor face) to achieve maximum control over the leading edge flow by varying individual injection parameters. The results show that at design speed (n=50000 r/min) with injection flow rate more than 2% of the main flow rate and yaw angle between 20° and 30°, the mass flow rate at stall decreases for approximately 8%. But with higher injection rate, other compressor parameters were affected such as compressor efficiency and compressor total pressure ratio.