A turbine with flow diverter comprises a support frame adapted to be anchored to a fixed or movable structure, an impeller rotatably mounted about a rotation axis to the support frame and having a front inlet section for receiving the flow and adapted to move continuously upon the rotation produced by the flow between a pushing position and an advancing position in correspondence of the front section, a main flow diverter adapted to be anchored to the support frame and having a peripheral wall adapted to at least partially blind the front section with respect to the flow auxiliary diverter extending from a first section facing one or more blades in the advancing position to a second section facing one or more blades in pushing position. The auxiliary diverter comprises curvilinear conduits in reciprocal side by side position along a radial direction.