Environmental Engineering Reference
In-Depth Information
13.1.1
Liquid Brakes
In 937, E. P. Culver from Princeton University,
conducted
research and experiments with hydraulic dynamometer also known
as water brake. He came up with a mechanical design and the
basic formula for water brake power:
3
5
P
=
k
*
v
*
d
, where
P
is the
power,
k
a factor depending on brake design,
v
the speed, and
d
the diameter of the rotor.
Water brakes are also used for purposes other than for
wind turbines. They are used in dynamometers, when measuring
efects of engines.
13.1.2
Water Brakes and Windmills
Throughout history there have occasionally been attempts to
develop wind turbines producing heat (hot water) instead of
electricity, the so-called water brake turbines. Water brakes
convert mechanical energy of the windmill into heat by friction in
the water. Water brake wind turbines can roughly be divided into
three groups:
() Do-it-yourself turbines
() Wind turbines constructed according to a design manual
(3) Industrially manufactured wind turbines
Water brake windmills are used to heat up buildings. They
are quite small with rotor diameters of maximum m may be
more. Windmills with water brakes operate according to the cube
power curve of the wind rotor as well as the rotor of the water
brake, which are the ideal operating conditions for both. They are
running with constant optimal tip-speed ratio.
When the maximum production is achieved, the efficiency
must be limited. This can be done either by letting the water brake
change its characteristics and overbrake. When this occurs, the
blades will stall. Another way to control the power is by letting
the blades pitch and the yield decreases.
The water brake windmill, with its power curve of three and
constant tip ratio, runs optimally on a much bigger wind range in
comparison with the simple stall regulated electricity-producing
Culver, E. P. (937)
Investigation of a Simple Form of Hydraulic Dynamometer
, in
Mechanical Energy, School of Engineering, Princeton University, p. 749.
Search WWH ::
Custom Search