Performance assessment of lift-based turbine for small-scale power generation in water pipelines using OpenFOAM

In-pipe water turbines have begun to gain interest for harvesting power on a small scale from pipe networks. However, few studies have addressed the feasibility of installing spherical lift-based helical-bladed turbines in a water supply network. Points such as the pressure drop and generated power remain unexplored. In this study, a three-dimensional numerical model, based on OpenFOAM, is used to investigate the performance of the spherical lift-based helical-bladed in-pipe water turbine. The study aims to evaluate how the geometric properties of this turbine affect its performance in terms of power and efficiency, and the hydraulics of pipe flow in terms of pressure drop. The study considers a turbine of diameter 600 mm, with the following geometric properties: number of helical blades 3, 4 and 5; blade chord length 10%, 15% and 20% of turbine diameter D; blade helicity 0 degrees, 60 degrees and 120 degrees; and pitch angle -6 degrees, -3 degrees, 0 degrees and 3 degrees. These parameters are analyzed at tip speed ratios (TSRs) of 2, 3 and 4. The results show that the five-blade turbine yields a power of 1300 W, while the three-blade turbine yields only 870 W, at an optimum TSR of 3. A change in the chord length of 50% (from 0.10D to 0.15D) increases the turbine power by 88.4% and efficiency by 40% for the same TSR. A further change to 0.20D gives no significant improvement in efficiency or power output. An increase in the helical angle from 0 degrees to 120 degrees results in a 22.8% reduction in turbine power. The turbine achieves the maximum power output of 1350 W at zero pitch angle, with a corresponding efficiency of 27%. The maximum head loss observed is 1.6 m, which represents 2.7% of the total head in the pipe. Solidity has a more pronounced effect on head losses than helicity and pitch angle.