The synthetic jet, located at the shroud and close to the blade leading edge, is used to control the flow in a typical centrifugal impeller. The effects of the synthetic jet control and the interaction with the tip leakage flow are mainly investigated at the near-stall working point of impeller using the unsteady numerical analysis. The results indicate that, the effect of the synthetic jet with a small injection angle (15deg) is better when the excitation position is located over the main blade leading edge. However, the synthetic jet with a large injection angle (90deg) obtains a better result when the excitation position is located at the downstream of main blade leading edge. The synthetic jet with a larger velocity amplitude has a more remarkable effect on deflecting the main flow/tip leakage flow interface to the downstream direction. With typical parameters, the synthetic jet increases the circumferentially averaged streamwise location of the main flow/tip leakage flow interface by 12.5% compared with the case without a synthetic jet. The interaction between the tip leakage flow and synthetic jet makes the tip leakage flow out of the tip clearance with larger streamwise momentum, which is favorable to restrain the tip leakage flow to spill out the leading edge. Besides, the periodic blade loading drop is deflected to downstream direction and the flow fluctuation near the leading edge decrease significantly with the presence of synthetic jet.

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