Wells turbine: Difference between revisions

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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 with its plane of symmetry in the plane of rotation and perpendicular to the air stream.

It was developed for use in Oscillating Water Column wave power 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 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 than asymmetric ones, even under optimal conditions. Also, in the Wells turbine, the symmetric airfoil runs partly under high angle of attack (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 of Queen's University Belfast in the late 1970s.

Annotation

Another solution of the problem of stream direction independent turbine is the Darrieus wind turbine (Darrieus rotor).

External links

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+{{Use dmy dates|date=April 2022}}
-[[Image:Wells turbine en.svg|thumb]]
+[[Image:Wells_turbine_de.svg|thumbnail|Wells-Turbine<br />1 pipe wall <br />2 Axis<br />3 Hub<br />4 Turbine blade<br />5 Resulting force vector<br />6 direction of rotation<br />7 air flow (can also be in the other direction)]]
-The '''Wells turbine''' is a low-pressure [[Wind turbine|air turbine]] that cannot rotate continuously in one direction in spite of the direction of the air flow. Its blades feature a symmetrical [[airfoil]] with its plane of symmetry in the [[plane of rotation]] and perpendicular to the air stream and the resulting aerodynamic force equaling zero or negative zero.
+The '''Wells turbine''' is a low-pressure [[Wind turbine|air turbine]] that rotates continuously in one direction independent of the direction of the air flow. Its blades feature a symmetrical [[airfoil]] with its plane of symmetry in the [[plane of rotation]] and perpendicular to the air stream.
-Unlike air, water is essentially incompressible...so what follows is horse shit and fairy dust:
 It was developed for use in [[Oscillating Water Column]] [[wave power]] 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]] 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]] than asymmetric ones, even under optimal conditions. Also, in the Wells turbine, the symmetric airfoil is used with a high [[angle of attack]] (i.e., low blade speed / air speed ratio), as it occurs during air velocity maxima in volatile flow. A high angle of attack causes a condition known as "[[Stall (flight)|stall]]" in which the airfoil loses lift. The efficiency of the Wells turbine in oscillating flow reaches values between 0.4 and 0.7.
+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]] than asymmetric ones, even under optimal conditions. Also, in the Wells turbine, the symmetric airfoil runs partly under high [[angle of attack]] (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 (flight)|stall]]" in which the airfoil loses lift. The efficiency of the Wells turbine in oscillating flow reaches values between 0.4 and 0.7.
-This simple but ingenious device was developed by Prof. [[Alan Arthur Wells]] of [[Queen's University Belfast]] in the late 1970s.
+The Wells turbine was developed by Prof. [[Alan Arthur Wells]] of [[Queen's University Belfast]] in the late 1970s.
 == Annotation ==
 Another solution of the problem of stream direction independent turbine is the [[Darrieus wind turbine]] (Darrieus rotor).
 ==See also==
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 == External links ==
-{{Commons|Category:Wells turbines|Wells turbines}}
+{{Commons category|Wells turbines}}
 * [http://www.archipelago.co.uk/our-work/wave-power-animation Animation showing OWC wave power plant"]
 * [http://www.overunity.com/13578/oscillating-water-column/msg363717/#msg363717]
 [[Category:Queen's University Belfast]]
 [[Category:Mechanical engineering]]