Abstract:
A theoretical investigation of aerodynamic performance
and design is carried out for vertical-axis straight-bladed
Darrieus wind turbines. Aerodynamic performance is performed
with blades of cambered;cross-section while design is conducted
with blades of symmetric cross-section. For the aerodynamic
analysis multiple streamtube theory and cascade theory are applied.
In order to choose the lift and drag coef.ficients for the
cambered blade profile, concept of thi@airfoil theory has been
applied.
A cascade principle ( Similar to that used in turbomachines)
with blades of cambered cross-section is applied for the performance
prediction of a vertical-axis straight~bladed Darrieus
wind turbine. By using the blades of cambered cross-section, the
lift force increases in the upwind side and decreases in the
downwind side in comparison to those for a turbine with symmetric
blade cross-section. As a result higher power is produced in
upwind side and lower power is produced in downwind side for a
turbine with cambered blade cross-section in comparison to those
for turbine with symmetric blade cross-s.ection •.However the
net power production is positive thereby making the higher efficiency.
The calculated results of. cambered blade cross-section
are compared with those of symmetric blade cross-section.
A design of a straight-bladed Darrieus. wind turbine with
blades of symmetric cross-section is performed. The design is
done at variable turbine speed condition. In order to mini mize the blade stress and with a view to use the low cost
material for blade manufacture the blade support.type
is considered to be overhanged type. It is observed from the
design analysis that this design with overhanged support
reduces the blade stress remarkably.
