Wind Energy

43 Aerodynamic Behaviour of a New Type of Slow-Running VAWT 239
Static torque coefficient
1.50
1.25
1.00
0.75
0.50
0.25
conventional rotor new rotor
0
0
−0.25
60 120 180 240 300 360
−0.50
Wind direction (˚)
Fig. 43.7. Torque on the optimised rotor (θ =90 ◦ ; β =45 ◦ ; e/d = 0.242; e ′ =0)
3.42e+01
2.82e+01
2.23e+01
1.63e+01
1.04e+01
4.39e+00
−1.57e+00
−7.53e+00
−1.35e+01
−1.95e+01
−2.54e+01
Fig. 43.8. Pressure contours (Pa) on the optimised rotor (θ =45 ◦ )
The choice of the three geometrical parameters e, e ′ and θ should be made
simultaneously not only to increase the aerodynamic efficiency but also to aim
an angular stability of the torque (future studies).
43.5 Conclusion
The flow around few conventional Savonius rotors has been modellised using
the CFD code Fluent v6.0. A geometry of an optimised rotor has been
proposed. Solutions have been presented to invent a new rotor, with higher
performances, by acting on the overlaps of the paddles and on their relative
inclination. This work must be continued, aiming a simultaneously research
of the optimum values of these geometrical parameters.
References
1. Wilson RE, Lissaman PBS. (1974) Applied Aerodynamics of wind power
machines. Research Appl. to Nat. Needs, GI-41840, Oregon State University
2. Menet JL, Valdès LC, Ménart B (2001) A comparative calculation of the wind
turbines capacities on the basis of the L–σ criterion. Ren. Eng. 22: 491–506