CFD based design of a 4.3MW Francis turbine for improved performance at design and off-design conditions

Hydraulic turbines are designed for the available head and flow rate of the hydroelectric power plant. Design point usually gives the best efficiency. However, when the turbine is used at off-design conditions where the flow rate and head change mostly because of seasonal fluctuations, efficiency significantly reduces. Therefore, the objective of hydraulic turbine design is not only satisfying the power requirements and maximum efficiency at the design point, but also improved characteristics at off-design conditions. In this work, a 4.3 MW Francis turbine is designed with the help of Computational fluid dynamics. All turbine components are designed separately, and then full turbine analyses are performed to confirm the design. Once an efficient design is obtained for the design head and flow rate, CFD simulations for off-design conditions are performed to confirm the high efficiency of the turbine at these flow rate-head combinations. The efficiency of the designed turbine is in the range of 90 to 92 % for a wide range of head and flow rates.