Computational and experimental performance analysis of a runner for gravitational water vortex power plant

Abstract

Energy generation through water is one of the most economic sources of power. On the other hand, isolated and rural communities can both benefit from using micro-hydropower to power their homes. The gravitational water vortex power plant (GWVPP) has recently attracted interest due to its low initial investment, straightforward design, simple maintenance requirements, and low head requirements. However, the technology suffers a low performance caused by unoptimised parameters of its crucial components, such as the GWVPP runner. This study presents the results of numerical simulation and experimental approaches for the GWVPP runner. To understand how each factor affected the efficiency of GWVPP runner, four parameters (hub-blade angle, speed, runner profile, and number of blades) were examined. The (custom) design tool of Design-Optimal Expert was used to create twenty-four (24) experimental runs. Commercial Computational Fluid Dynamics (CFD) software, specifically Ansys CFX, was employed to simulate these runs and assess the system's efficiency. R2 values of 0.9507 and 0.9603 for flat and curved profiles indicate a better model fitting to actual data. Additionally, the numerical analysis led to a 3.65% improvement in the efficiency of the curved blade profile runner, while the flat runner profile's efficiency increased by 1.69% compared to non-optimized scenarios. The validation process revealed that the comparison between the numerical investigation and experimental results demonstrated a promising agreement, further supporting the accuracy of the numerical analysis. The experimental finding depicts that the efficiency was 9.84 - 25.35%, torque was 0.08 – 0.23 Nm, and the output power was 2.96 – 7.33 W. Furthermore, the results portray the numerical efficiency to be slightly greater by 0.54% than the experimental efficiency, presumably because the frictional forces were not incorporated in the numerical analysis. Additionally, the exergy analysis of the system revealed a value of 43.58%. The power error range was between 0.1 and 0.5 W, with a low variation in the data points. The torque error range was relatively lower than the power error range, ranging from 0.01 to 0.03 Nm, and the torque measurements showed a low variation in the data points. The efficiency error range was generally low, with most errors falling within the 1.3-3.1% range. Therefore, the GWVPP runner efficiency can be improved significantly through numerical analysis and experimental studies. Also, based on the above results, the GWVPP runner and GWVPP system are recommended for energy generation in low-head and flowrate water sources.