Numerical analysis of cavitation hydrodynamics at different Kaplan runner solidity

The power developed by turbine is mainly affected by the runner design (including blade profile and runner solidity) and its rotational speed. However, the solidity of runner greatly affects the hydraulic efficiency as well as the cavitation performance of the turbine. Thus, the most crucial aspect of hydraulic turbine design is to ensure efficient and cavitation-free operation. The objective of proposed work is to analyze the effect of runner solidity on cavitation characteristics and hydrodynamic parameters to obtain the optimal number of runner blades for Kaplan turbine. The computational efficiency and value of critical cavitation factor at the rated operating condition are also compared with experimental results for validation and found to bear the close comparison. The critical analysis of various flow parameters for cavitating and non-cavitating analysis is also presented. The values of critical cavitation factor are found to be 0.58, 0.39, 0.26 and 0.18 for 3, 4, 5 and 6 number of runner blades, respectively. It is found that the critical cavitation factor decreases as the runner solidity increases. In addition to this, the effect of runner solidity on the location of cavitation is also investigated. The proposed work is very realistic and suited for the actual site conditions.