Читать книгу Wind Energy Handbook - Michael Barton Graham - Страница 102

Another parameter that affects the power output is the pitch setting angle of the blades β_s. Blade designs almost always involve twist, but the blade can be set at the root with an overall pitch angle. The effects of a few degrees of pitch are shown in Figure 3.58.

Figure 3.56 Effect on extracted power of rotational speed.

Figure 3.57 Effect on extracted power of rotational speed at low wind speeds.

Figure 3.58 Effect on extracted power of blade pitch set angle.

Small changes in pitch setting angle can have a dramatic effect on the power output. Positive pitch angle settings increase the design pitch angle and so decrease the angle of attack. Conversely, negative pitch angle settings increase the angle of attack and may cause stalling to occur, as shown in Figure 3.58. A turbine rotor designed to operate optimally at a given set of wind conditions can be suited to other conditions by appropriate adjustments of blade pitch angle and rotational speed.