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Forum Index : Windmills : savonius gap ratio

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mechamz
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Joined: 29/06/2008
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Posts: 11
Posted: 05:07am 17 Sep 2008
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there is a support beam in the centre of the turbine blades, and the diameter is 2cm. the bucket gap width is 6cm, the diameter of turbine is 44cm, and the height of the turbine blade is 80cm.

when calculating the "gap width ratio, s/d", do I need to take the diameter of the support beam into consideration?

so my gap width ratio = (bucket gap width,s - diameter of support beam) / diameter of turbine ??

or just ignore the diameter of the support beam?

thanks

looking for low rpm alternator
I'm looking for an alternator(low rpm) pm me please
 
Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669
Posted: 09:30am 17 Sep 2008
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G'day mechamz,
I recall this information is redily available on sites that appear near the start of Googles response to a search on 'savonious'. I don't have the site bookmarked so would need to find it again. It's easy to find so I won't do it as I feel something that easy and basic is your job.

Happy hunting.
was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
 
mechamz
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Joined: 29/06/2008
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Posts: 11
Posted: 02:02pm 17 Sep 2008
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  Gill said   G'day mechamz,
I recall this information is redily available on sites that appear near the start of Googles response to a search on 'savonious'. I don't have the site bookmarked so would need to find it again. It's easy to find so I won't do it as I feel something that easy and basic is your job.

Happy hunting.


Hi,

Thanks. I have did a lot of research on that..
But I'm wondering do I need to consider the diameter of the beam??
I'm looking for an alternator(low rpm) pm me please
 
grub
Senior Member

Joined: 27/11/2007
Location: Australia
Posts: 169
Posted: 09:28pm 17 Sep 2008
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I remember reading that the overlap is 29% but the support tube needs to be accounted for (added to the overlap). The person who reached the 29% did so by setting his rotor up on a vehicle and driving at a set speed, then adjusted the gap and retested. Not sure where I found this info but it stuck in my memory.
 
Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5117
Posted: 11:18pm 17 Sep 2008
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I do think the beam diameter needs to be taken into account. There is a lot of air that wants to move through that gap, so any obstacle will reduce the designs efficiency.
I would try to use the smallest diameter beam I could, or get rid of it all together. Could you use 4 smaller beams, one at each edge of each shell?

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ
 
windlight
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Joined: 03/03/2007
Location: Australia
Posts: 331
Posted: 11:51pm 17 Sep 2008
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The beam represents an orifice to the air flow, as the air encounters the beam the air is compressed and the velocity increases, as the air leaves it expands and slows.

As with any orofice it does presesnt as a restriction but without doing the maths I would guess you need to allow 10% of the beam diamiter.

A link if it works, not straightforward but....
http:http://www.trident.on.ca/orifice-air-

allanEdited by windlight 2008-09-19
"I like this place and willingly could waste my time in it" - (Act II, Scene IV).
 
mechamz
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Posted: 03:43pm 18 Sep 2008
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  windlight said   The beam represents an orifice to the air flow, as the air encounters the beam the air is compressed and the velocity increases, as the air leaves it expands and slows.

As with any orofice it does presesnt as a restriction but without doing the maths I would guess you need to allow 10% of the beam diamiter.

A link if it works, not straightforward but....
http:http://www.trident.on.ca/orifice-air-

allan


the link is not working
I'm looking for an alternator(low rpm) pm me please
 
windlight
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Joined: 03/03/2007
Location: Australia
Posts: 331
Posted: 10:53am 19 Sep 2008
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OK google "air flow through orifice", you will have to multiply the information up to your dimensions but it will give you an idea.

allan
"I like this place and willingly could waste my time in it" - (Act II, Scene IV).
 
Jarbar
Senior Member

Joined: 03/02/2008
Location: Australia
Posts: 225
Posted: 09:03am 20 Sep 2008
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Mechamz,
This site may shed some light as well.

http://www.aeromech.usyd.edu.au/aero/introvisc/node6.html#no de9

Jarbar
"Creativity is detirmined by the way you hold your tounge".My Father
"Your generation will have to correct the problems made by mine".My Grandfather.
 
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