Stall mitigation and performance enhancement in axial-flow air turbines using a hybrid passive–active flow control strategy

Harvesting maximum energy from axial turbines remains a significant challenge, particularly under stall conditions. Wells turbine, commonly used as self-rectifying axial turbine in wave energy conversion (WEC) systems, is limited by a narrow operating range, low power output, and reduced aerodynamic performance. To address these issues, passive, active, and hybrid flow control strategies are numerically investigated using steady Reynolds-Averaged Navier–Stokes (RANS)-based computational fluid dynamics (CFD) simulations to mitigate flow separation and enhance performance. A leading-edge micro-cylinder is used as a passive flow control device, while a dielectric barrier discharge (DBD) plasma actuator is employed for active control. The hybrid configuration combines both techniques, with the micro-cylinder positioned near the leading edge at a distance of 3.38% of the chord length and the plasma actuator mounted on the blade surface at 13.2% of the chord length. A comprehensive comparison is conducted among passive, active, and hybrid flow control strategies. The results indicate that the hybrid approach more effectively delays flow separation, improves flow attachment, and enhances turbine performance compared to the individual methods, thereby offering a promising solution for extending the operational range of these turbines. The results indicate that the hybrid flow control strategy increases the peak and average power coefficients by 105% and 103%, respectively, compared to the baseline turbine, and extends the stable operating range by 44.4%.