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homebrew hydro update: coanda water intake - Page 5

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Posted by z on February 25, 2009, 6:35 am

well for the price its well worth playing around.  I can always use them
for something.  Might be just the thing for when I'm restricting usage as
summer comes on.  I'm jazzed to see how they work.

Well I do have a very crap PSI gauge so who knows.  I think its about 100
feet elevation from the pond and about 400 feet of pipe. With a bigger
pipe I can move more water, maybe add a third jet.

As you know i've been winging this thing from the start.  Just using that
estimater program from canada which shows almost a doubling of potential
energy from 1.5 inches to 2 inches.


Posted by Bob F on February 26, 2009, 3:40 am
z wrote:

Do you have a reading for pressure under zero flow. The difference between that
and your operating pressure reading would give you a good idea of your losses.
If there is little difference, the larger pipe won't help much at the flow rate
you are operating.

Posted by harry on February 24, 2009, 8:23 pm
The thread is probably British Standard Pipe thread. If it's 3/4"
diameter overall, it will be 1/2" BSP.  If you can't get a
corresponding thread  locally  just soft solder a local copper fitting
over the thread. File a bit off  the thread if neccesary.

The valve you want is a needle valve.

Posted by Johnny B Good on February 24, 2009, 10:47 pm
 The message

====big snip===

 The description is rather meagre, failing to mention their major
benefit in flow control in a pelton turbine where the last thing you
need is an ability to dump the water from your penstock as fast as the
pipework will allow.

 The needle valve is ideal for metering the mass of water being
delivered to the pelton runner without significantly altering the
velocity of the water jet. It does this by varying the effective cross
sectional area of the exit nozzle.

 Generally, with a pelton wheel driven generator, you want control of
the drive torque without undue variation of speed in order to adjust for
variations in load at a constant voltage.

 Broadly speaking, a doubling of demanded current from the generator
will require a doubling of applied torque which you want to achieve by
doubling the mass of water flowing per unit of time at a fixed water jet
velocity. The needle valve approximates to this ideal characteristic far
better than any other control valve.

 Throttling the flow upstream of a fixed sized orifice jet introduces
unwanted speed variations in the water jet, causing reduced operational
efficiency with conventional PM alternator/ pelton runner turbine
setups. Although it is possible to mitigate the losses in such a scheme
(use of variable speed water jets) by using switching voltage converter
circuitry, the efficiency will still suffer some compromise, despite the
additional complexity.

 If you want to get the most out of a micro hydroelectric pelton wheel
based genset, you'll have to employ needle jet valve control in the

Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

Posted by harry on February 24, 2009, 8:38 pm
You might find this interesting also:-

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