Smart optimization algorithms to enhance an axial turbine performance for wave energy conversion

Abstract

One of the potential options for usage in wave energy conversion systems of the oscillating water column (OWC) type is the Wells turbine. Because of its relatively small output power and limited operating range, the cost of producing power increases, so the Wells turbine can only be used in a few ocean locations. Early deterioration of the turbine's performance resulted from the early turbine stall, which limits the power produced and the operating range because it does not operate in stall conditions. The current work aims to increase the Wells turbine's output power and operating range through a new turbine design. This design aims to integrate variable tip clearance design and casing groove design. A response surface optimization technique based on computational fluid dynamics (CFD) is used to determine the optimum dimensions of the new design. The present study utilized the toolbox for response surface optimization of the ANSYS software. Five geometrical parameters for the new turbine design were used as inputs for the optimization approach. At a flow coefficient of 0.250, the optimization technique sought to optimize the Wells turbine's torque coefficient (CT). The Wells turbine's average and maximum torque coefficients are improved by 39.13% and 74.32%, respectively. Compared to the typical design, the optimized design expands the operating range (OR) of the Wells turbine by 33.33%. The torque coefficient and efficiency of the enhanced Wells turbine increase by 82.97% and 71.64%, respectively, at a flow coefficient of 0.250. The torque coefficient modification factor of the enhanced Wells turbine is increased by 94.78% compared to the typical turbine. Based on a detailed flow analysis, the optimal new design reduces the axial flow velocities near the suction side on most of the blade span, which delays the flow's separation toward the trailing edge, which delays the inception of the enhanced turbine stall.