The Wells turbine is a low-pressure
air turbine that rotates continuously in one direction independent of the direction of the air flow. Its blades feature a symmetrical
airfoil
An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine.
...
with its plane of symmetry in the
plane of rotation
In geometry, a plane of rotation is an abstract object used to describe or visualize rotations in space. In three dimensions it is an alternative to the axis of rotation, but unlike the axis of rotation it can be used in other dimensions, such as ...
and perpendicular to the air stream.
It was developed for use in
Oscillating Water Column
Oscillating water columns (OWCs) are a type of wave energy converter that harness energy from the oscillation of the seawater inside a chamber or hollow caused by the action of waves. OWCs have shown promise as a renewable energy source with low e ...
wave power
Wave power is the capture of energy of wind waves to do useful work – for example, electricity generation, water desalination, or pumping water. A machine that exploits wave power is a wave energy converter (WEC).
Waves are generated by wind p ...
plants, in which a rising and falling water surface moving in an air compression chamber produces an oscillating air current. The use of this bidirectional turbine avoids the need to rectify the air stream by delicate and expensive
check valve
A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.
Check valves are two-port valves, meaning they have t ...
systems.
Its efficiency is lower than that of a turbine with constant air stream direction and asymmetric airfoil. One reason for the lower efficiency is that symmetric airfoils have a higher
drag coefficient
In fluid dynamics, the drag coefficient (commonly denoted as: c_\mathrm, c_x or c_) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equ ...
than asymmetric ones, even under optimal conditions. Also, in the Wells turbine, the symmetric airfoil runs partly under high
angle of attack
In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
(i.e., low blade speed / air speed ratio), which occurs during the air velocity maxima of the oscillating flow. A high angle of attack causes a condition known as "
stall" in which the airfoil loses lift. The efficiency of the Wells turbine in oscillating flow reaches values between 0.4 and 0.7.
The Wells turbine was developed by Prof.
Alan Arthur Wells
Alan Arthur Wells (1 May 1924 – 8 November 2005) was a British structural engineer.
Early life
He was born in Goff's Oak, Hertfordshire to Arthur John Wells, a British Oxygen Company engineer and educated at the City of London School as a day ...
of
Queen's University Belfast
, mottoeng = For so much, what shall we give back?
, top_free_label =
, top_free =
, top_free_label1 =
, top_free1 =
, top_free_label2 =
, top_free2 =
, established =
, closed =
, type = Public research university
, parent = ...
in the late 1970s.
Annotation
Another solution of the problem of stream direction independent turbine is the
Darrieus wind turbine
The Darrieus wind turbine is a type of vertical axis wind turbine (VAWT) used to generate electricity from wind energy. The turbine consists of a number of curved aerofoil blades mounted on a rotating shaft or framework. The curvature of the bla ...
(Darrieus rotor).
See also
*
Siadar Wave Energy Project
The Siadar Wave Power Station (also known as Siadar Wave Energy Project or SWEP) was a proposed 4 MW wave farm off the shore of Siadar Bay, in Lewis, Scotland. The £30 million project, was to be built by Wavegen, received Scottish ...
*
Yoshio Masuda Yoshio Masuda (died 2009) was a former Japanese naval commander, regarded as the father of modern wave power technology. Among other devices, the now used principle of Oscillating Water Column is regarded as his invention. It was initially used for ...
Hanna Wave Energy Turbinefree 3D design to print your own
External links
{{Commons category, Wells turbines
Animation showing OWC wave power plant"
Queen's University Belfast
Mechanical engineering
Turbines
Power station technology
Renewable energy technology
Water power
Electrical generators