The rotor power coefficient is regarded as the energy transformation efficiency. The
KR vertical-type wind turbine is designed to operate within 0.4 and 0.6 tip speed ratio
to achieve the highest rotor efficiency ever developed.
Principles of Jet-Wheel-Turbo Turbine
The incoming wind flow-rate should be equal to the outgoing flow-rate to satisfy
the mass conservation law if a control volume around a turbine is assumed. The
outgoing wind-speed distribution and its direction strongly determine the turbine
efficiency. As can be seen in Fig. 1, the upstream area (A
1
) is smaller than the rotor
area (A
2
) of the same stream tube due to the rotation of the rotor, thereby resulting in
unavailable wind energy upstream. The momentum transfer, which can be computed
by the difference of the upstream and downstream wind speeds, may be maximized
by reducing the wind speed (V
3
) in the wake.
Fig. 1 Stream tube passing the rotor plane
The inlet- and side-guide vanes of the KR turbine are designed to make the
streamlines as parallel to each other as possible (A
1
A
2
), and the rotor wake is
minimized by discharging the air through the upper and bottom openings of the
rotor
(7)
.
KR 1kW VAWT Model Specifications
The technical details of 1kW model are described in Table 1. The furling tail is
attached to the guide-vane system which is passively forced to rotate by the stabilizer.
Similarity of Incoming Flows to Turbine
To determine the deceleration ratio of the velocity in front of the turbine to the
free stream wind velocity, a numerical simulation was carried out for a turbulent flow
Summary :
1 Stream tube passing the rotor plane The inlet- and side-guide vanes of the KR turbine are designed to make the streamlines as parallel to each other as possible (A 1 A 2 ), and the rotor wake is minimized by discharging the air through the upper and bottom openings of the rotor (7) .
Tags :
turbine,rotor,wind,efficiency,upstream,stream,designed,energy,tube,outgoing,elocity,area,fig