The effect of blade depth ratio on the performance of in-stream water wheels

Abstract

The power characteristics of an in-stream water wheel were measured experimentally to explore the influence of the blade depth ratio. The blade depth ratio has a significant effect on the performance of in-stream water wheels, but its influence has been overlooked throughout the literature. It was determined that the blade depth ratio has a greater impact on the power production than the number of blades at all tip-speed ratios. However, the variation between the maximum and minimum available power is greater at high blade depth ratios, so it is important to understand the relationship between the blade depth ratio and tip-speed ratio. Analysis of velocity triangles determined that at the inlet and outlet, the turbine blade contributes negatively to net torque. This effect is increased at higher blade depth ratios. It was also determined that the peak dry coefficient of power is linearly proportional to the blade submergence ratio, which is a measure of the total submerged blade area. This investigation progresses research in this area by highlighting an overlooked parameter and experimentally determining its influence on power characteristics.