Experimental research regarding the performance of small axial turbines

This paper continues research of the authors and presents some theoretical aspects regarding the maximum power extract from the wind turbines, the optimal incidence angle, the best twisting of the blade and experimental research done in the laboratory of Renewable Energy from the Hydraulics, Hydraulic Machineries and Environmental Engineering Department, on small axial turbines, with impeller of 500 mm and 2000 mm in 3 constructive variants: with 3, 4 and respectively 8 blades. These turbines can have applications both aerodynamic - wind turbines but also hydrodynamic.It was determined the provided power, the starting / braking torque of the impeller and the power coefficients for these three type of turbines. From the experimental research resulted that the best behavior had the small impeller of 500 mm, with four bladed with cp = 0.56, tested in water, than the 500 mm impeller with three blades having the power coefficient cp = 0.43, tested in air and the last impeller, with 2000 mm and 8 bladed, has about cp = 0.4, tested in air too. These experimental results are the basis of various aerodynamic and hydrodynamic applications and further research.