Wind Energy

33 Experimental Researches of Characteristics of Windrotor Models 185
It is necessary to note also, that for all considered flow velocities the
hydrotray rotors with controlled blades have self-started, while rotors with
rigidly fixed blades must be spin upped, i.e., certain auxiliary torque M must
be applied on the windrotor model shaft. Only after that a rotor continued
rotation with constant revolution velocity.
The dependencies Cp on Z for windrotor models with 2, 3, and 4 blades are
presented in Fig. 33.1. It appeared, that the positional relationship of curves
Cp(Z) for windrotor models with various numbers of blades essentially differ
from that of similar curves for windrotor model with rigidly fixed blades.
For the last, increasing number of blades leads to a shift of the right part of
dome-shaped curve Cp(Z) to the left (i.e., reduces rapidity of a wheel), and
on the contrary happens for windrotor models with controlled blades. Here
the least high-speed has appeared for the rotor with 2 blades. The greatest
values of both the operating ratio of flow energy Cp and the coefficient of
windrotor torque Cm ware received just for the windrotor models with 3 and
4 blades.
The influence of the mechanism of windrotor blades control on the magnitude
of the torque gained by a windrotor is especially great. The graphs
Cm(Z) in Fig. 33.2 show that for both windrotor models with 3 and 4
Cp
0.15
0.1
0.05
model N1
4 bl.-fix.
3 bl.-fix.
2 bl.-fix.
4 bl.- cont.
3 bl.- cont.
2 bl.- cont.
0
1.0 1.5 2.0 Z 2.5 3.0 3.5
0.2
0.15
Cp
0.1
0.05
model N2
4 bl.-fix.
3 bl.-fix.
2 bl.-fix.
4 bl.- cont.
3 bl.- cont.
2 bl.- cont.
0
0.5 1.0 Z 1.5 2.0
Fig. 33.1. Dependencies of operation ratios of the flow energy Cp on coefficient of
specific speed Z (flow velocity in hydrotray V =0.6ms −1 )
Cm
0.125
0.1
0.075
0.05
0.025
model N1
4 bl.-fix.
3 bl.-fix.
2 bl.-fix.
4 bl.-cont.
3 bl.-cont.
2 bl.-cont.
0
1.0 1.5 2.0 Z 2.5 3.0 3.5
Cm
0.3
0.25
0.2
0.15
0.1
0.05
model N2
4 bl.-fix.
3 bl.-fix.
2 bl.-fix.
4 bl.-cont.
3 bl.-cont.
2 bl.-cont.
0
0.5 1.0 1.5 Z 2.0 2.5
Fig. 33.2. Dependences of coefficients of windrotor model torque Cm on coefficient
of specific speed Z (flow velocity in hydrotray V =0.6ms −1 )