Page 45 - Fluid Power Engineering

Basics of W ind Energy and Power 23

FIGURE 2-10 Vertical
axis wind turbine. r
The height of blade
is h and diameter of
rotation is 2r = d.
h

Assume a jet of water with speed v 0 strikes blades of Pelton wheel
rotor as shown in Figure 2-11. Assuming a frictionless surface on the
blade, the output speed of water will remain v 0 .
According to Newton’s second law, the force required to change
the momentum is:

F = ˙m (−v 0 − (+v 0 )) =−2˙mv 0 (2-39)
where ˙m is the mass of water that hits a stationary blade every second.
Because the blade is moving, the speed of water relative to the blade

ν 0 ν 0

Water jet

Center of rotation
Pelton Wheel
blade
ω

u
FIGURE 2-11 Illustration of a Pelton wheel hydrorotor.