Hydraulic Behavior and Performance of Breastshot Water Wheels for Different Numbers of Blades

Abstract

Thanks to their efficiency and simplicity of contruction, breastshot water wheels represent an attractive low head hydropower converter. In this work, a breastshot wheel is investigated by numerical simulations, and the results are validated with experimental tests. The average discrepancy between the numerical shaft torque and the experimental torque is lower than 5%. The numerical model is then used to investigate the performance and the hydraulic behavior of the wheel for different numbers of blades (16, 32, 48, and 64 blades) and at different hydraulic conditions. The increase in efficiency from 16 blades to the optimal blades number ranges between 12 to 16% in function of the hydraulic conditions. Empirical laws are also reported to quantify the improvement in efficiency with the blades number. These laws can support the design process of similar breastshot water wheels. The optimal blades number for this kind of wheel is identified in 48.