Influence of Number of Blades on Performance and Internal Flow of High Head Contra-Rotating Small Hydroturbine

抄録

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 a small hydroturbine suitable for low flow rate and high head, we propose 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 number of blades of the hydroturbine composed of these rotors as a first step of this research, and investigate performance by numerical analysis. As a result, it clarifies that the head of the front rotor is lowered due to the slip of the flow, and it has been confirmed that increasing the number of blades can suppress the slip of flow and improve the turbine head and the shaft power. Also, it clarifies that the shaft power of the rear rotor was almost unchanged even if the number of blades is changed, and that the meridional plane shape has a greater effect on the performance than the number of blades.