DEVELOPMENT OF SMALL WIND TURBINE USING CURVED-PLATE BLADED ROTOR -PERFORMANCE AND VISUALIZATION OF AIR FLOW USING PIV ANALYSIS

Abstract

The  authors  have  developed  a  simplified  curved-plate  blade  of  high  power  coefficient  for  small  wind  turbine depending on the design concept of the “Appropriate Technology (AT)”. In this study, the shapes of blade are the tapered type, the straight type and the inversely tapered type and the diameter of all experimental model is 600[mm], number of blades is 5, thickness of plate is 2[mm]. The bent angles of these three types of the blades are 10, 20 and 30[deg] respectively. Blades pitch angle can be changed manually at 0, 5, 10 15, 20 and 25[deg]. In the experiment of all rotors, the wind speed in the wind tunnel is set at 10[m/s] and the torque and the corresponding to rotational speed was measured by gradually increasing the load. From the results of the experiment, the power coefficient Cp and the tip speed ratio λ were calculated to obtain the power characteristics for different blade types. In these result, the maximum power coefficient for tapered type is Cpmax=0.278 when bent angle is 30[deg] and blade pitch angle is 10[deg]. Thus, straight  type is Cpmax=0.303  when  bent  angle  is 30[deg] and blade pitch angle  is 15[deg]. And inversely tapered type is Cpmax=0.338 when bent angle is 30[deg] and blade pitch angle is 15[deg]. The most efficient model was inversely tapered type. Moreover, to clarify the details of air flow around the each rotor for the maximum power coefficient,  the  authors conducted  through  visualization  test using  the  smoke oil,  high-speed  camera  and vector analysis using the P.I.V. system. From the visualization test and P.I.V. analysis, it was clarified that the wind speed of inflow around tip of tapered type is about 7.5[m/s], on the other hand, inversely tapered type is about 8.0[m/s]. From these results, it could presume that the latter type is more effectively converting the air flow into the shaft power than that of the former type.

Key words: Curved plate blade, coefficient of power (Cp), tip speed ratio, bending and pitch angle, P.I.V. system