Optimization of the Inlet Velocity Profile in a Conical Diffuser

Past numerical and experimental research has shown that the draft tube inlet velocity has a critical importance in the hydropower plants performance. However, there is a lack of information in terms of flow parameters and in particular of swirl distribution. With regards to the overall performance of a turbine, the optimization of the inlet velocity profile constitutes a new approach to control the inlet flow conditions to yield better draft tube and turbine performance. Numerical optimization methods have been successfully used for a variety of design problems. However, the optimization of boundary conditions in hydraulic turbines is a new challenge. Thus a detailed research of the optimization methodology is the aim of this paper. Three different vortex equations to represent the inlet velocity profile are applied to a cone diffuser and the behavior of the objective function is analyzed. A discussion concerning the development of a flow structure caused by the inlet swirl parameters is included.