Performance Analysis of Wells Turbine With Radiused Blade Tip

A Wells turbine is an axial flow reaction turbine, which consists of a symmetrical airfoil at 90° stagger. It is commonly used as a power take-off device in the oscillating water column. This turbine is prone to stall at higher flow coefficients and have narrow operating range. There are several parameters, which influence the stall characteristics of the turbine, one of them is the tip leakage flow. Radiused blade tip was shown to suppress separation bubble and mitigate internal gap loss. In this study, the aerodynamic characteristics of Wells turbine with radiused blade tip were investigated. The numerical analysis was done by solving three-dimensional steady Reynolds-averaged Navier-Stokes equation with k-ω SST turbulence model. The turbine with blade profile NACA 0015 was taken as the reference blade, and the numerical results were validated with the experimental data. Radiused tip blades with different fillet radius were analysed and they showed similar performance. They improved the operating range and peak torque coefficient by 25% and 37% respectively. The fluid dynamics behind the performance augmentation was also analyzed and reported.