Wind Energy

238 J.-L. Menet
3.42e+01
2.82e+01
2.23e+01
1.63e+01
1.04e+01
4.39e+00
−1.57e+00
−1.53e+00
−1.35e+01
−1.25e+01
−2.54e+01
Fig. 43.5. Pressure contours (Pa) on the optimised rotor (θ =90 ◦ )
Fig. 43.6. Static torque coefficient on the optimised rotor
is found to be equal to 0.242, whereas e ′ = 0. Even if it remains very instable,
the torque coefficient is notably raised compared with the conventional
Savonius rotor [4], with a general increasing of about 20%.
43.4.2 The New Rotor
In this preliminary work, the influence of the inclination angle β of the paddles
has been studied for only two values of the wind direction: θ =90 ◦ and θ =45 ◦ ,
that allows to determine an optimal value of the inclination angle: β =55 ◦ .
Optimum values of the overlaps giving highest values of the torque, have been
systematically researched, leading to: e/d = 0.242 and e ′ = 0. The static torque
is calculated as in Sect. 43.4.1. (Fig. 43.7). An example of the pressure contours
is presented in Fig. 43.8.
The result is encouraging, since the new rotor induces maximal values of
the static torque largely higher than those obtained on the conventional rotor,
even if it also introduces low and negative values of this torque, with a great
angular variation. Nevertheless, the mean value of the torque is increased:
Cm = 0.48, i.e. 60% more than for the conventional rotor.