Performance Prediction of a Micro Francis Turbine Including Off-Design Conditions Using Commercial Cfd Code

Low-head micro-hydro systems for energy production have drawn greater attention worldwide because of oil crises and new advances in their design and efficiencies. Due to availability of huge hydro potential in North Eastern region, Govt. of India has taken a greater initiative to harness the available potential of pico to small hydropower resources. It is desirable that the hydro turbines to be put into operation over this region would run efficiently even under different flow situations. To fulfill this requirement, it is essential to test and validate the optimal conditions and the hydrodynamic behaviour of the system through rigorous laboratory testing in conforming to available flow conditions prevailing at site.

As this is still a new area for development, to make the design and testing cost effective and time efficient, attempts are made to predict the turbine behaviour through numerical simulations. This paper highlights typical numerical experimentations in commensurate with an existing turbine that is installed and functional in our laboratory. The present study investigates the capability and consistency of steady state CFD simulation following Realizable k-e model in the context of performance prediction of micro Francis turbine. The performance characteristics of a micro Francis turbine have been obtained from laboratory experiments by covering a wide range of operating conditions including off-design conditions. CFD analysis on the entire turbine domain is also performed. The experimental and CFD outcomes are converted into unit quantities and compared accordingly to establish the zone for maximum efficiency. The results show good agreement in terms of efficiency, prediction of the maximum efficiency zone and other performance parameters of the turbine. In conclusion, CFD can be employed as an alternative means for designing and development of new types of turbines most effectively.