Influence of meridional plane shape on performance and internal flow of high head contra-rotating small hydroturbine

It is requested that the hydroturbine be a small size and have high performance. Therefore, we adopted contra-rotating rotors, which can be expected to achieve radial compactification and high performance. However, a conventional contra-rotating rotor was composed of two axial flow rotors, so it had a specification suitable for high flow rate and low head. In order to achieve small hydroturbine suitable for low flow rate and high head, we propose a new type of contra-rotating rotors, which are composed of a hybrid rotor and a centrifugal rotor. In the present paper, we focus on the meridional plane shape at the connection between the front rotor and the rear rotor of the hydroturbine composed of these rotors as a first step of this research, and investigate performance by the numerical analysis. As a result, we clarified that the relationship between the performance and internal flow when the blade width at the connection between the front rotor and the rear rotor changed.