Advanced Wind Turbine Program Next Generation Turbine ... - NREL

Power Production [kW
1,500
1,000
500
0
Steady Winds
9% Turbulence
0 5 10 15 20 25 30
Wind Speed [m/s]
Figure 37. Predicted Power Performance for the EMD1.5/77 Turbine
4.2 EMD1.5/77 Component Designs
4.2.1 EMD Gearbox Modification
To maintain the rotor tip speed at the baseline value of 73.8 m/s when operating at rated power,
the gear ratio was increased to 78.25:1 rpm. The gearbox supplier analyzed the gearbox and determined
that the change could be effected by modifying the third stage only. The first stage
gear can accommodate the increased ultimate loads.
4.2.2 EMD 37-m Rotor Blade Design and Testing
Several approaches to designing the 37-m blades were considered, including adding material to
either or both of the root and the tip of the GE34a blade. GE finally decided to choose the approach
motivated by energy capture and add all of the 3.25 m of new blade to the tip. The contour
is exactly the same as that of the GE34a blade out to the 30.95-m spanwise location. Details
of the blade geometry are shown in Figure 38. The GE37a blade employs another innovative
feature: blade curvature. During the concept studies (see Section 2.3) it was noted that one alternative
to blade coning is the use of blade curvature, that is, gradually curving the blade out of the
rotor plane. For the GE37a blade, such curvature is only employed at the tip of the blade in order
to provide a small amount of additional tower clearance. This is needed because of the extra
length of the blade. The blade still employs 1.3° of forward precone in the root.
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