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Member

Join Date: Dec 2011
Posts: 6

Waterwheel Dimension

12/28/2011 12:24 PM

I am a student of engineering. My lecturer assigned me to produce a prototype of floating waterwheel river turbine that connected to a 3-phase permanent magnet generator. It is necessary for this generator to generate constant power of 500Watt to charge 12V battery. the water flow at constant speed of 2m/s. emf constant for generator I calculate is 0.06 V/rpm. Can anyone give me the formula for me to calculate the dimension (height, radius of waterwheel and width of the blade) of the waterwheel I need to built to get this amount of power.

Pathfinder Tags: Waterwheel Calculation
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#1

Re: Waterwheel Dimension

12/28/2011 12:31 PM

If you keep doing what you always did, you'll keep getting what you always got.

Why not take a shot at it and see what you come up with. No one's going to help you if you don't try to do it by yourself first, then report what you found and maybe someone will help/guide you.

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#2

Re: Waterwheel Dimension

12/28/2011 1:47 PM

the problem is, I don't have the formula for getting the dimension of the waterwheel. I have calculated other thing. It like a general assignment that we need to do our own research. I try to google the formula for waterwheel dimension but not found. Besides, this project is out of syllabus in class. I am a mechanical engineering student but I need to learn an electrical subject. So, if you guys know any formula regarding waterwheel dimension that will help me a lot.

I just try my luck here if there is anybody who have built a waterwheel before might have a formula for their dimension

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#10

Re: Waterwheel Dimension

01/10/2012 7:23 AM

OK. So do an energy balance. 500W on the wires is >500W from the fluid flow. Call the conversion efficiency 25%. The drop in height is known, so the volumetric flowrate can be calculated and so can the flux. The speed of the shaft must be available. Assume plug flow, and out drops the width - it's only arithmetic.

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#3

Re: Waterwheel Dimension

12/28/2011 2:09 PM

Try some of these

Do some research and let us know what you find.

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#4

Re: Waterwheel Dimension

12/28/2011 2:25 PM

Don't get hung up on the electrical part of this problem. Check out my reply in your identical thread.

(A repeated thread and a homework problem. I'm a little embarrassed now for the answer I gave.)

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#5

Re: Waterwheel Dimension

12/28/2011 6:34 PM

To charge a 12V battery, the generator must put out somewhat more than 12V. This will tell you how fast the generator must turn. The waterwheel blades will slip somewhat, maybe going about 2/3 as fast as the water passing by. This will allow you to estimate the wheel's diameter.

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#6

Re: Waterwheel Dimension

12/28/2011 11:29 PM

If you're going to post on this site, read the FAQ's. Don't post the same question in multiple forums-you lose creditability doing so.

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#7

Re: Waterwheel Dimension

12/29/2011 12:39 AM

In addition, you can compute the kinetic energy of area A x 2m of water per second. Guessing 50% efficiency, equate this to 1000 watts, and this will estimate the required blade area.

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#8

Re: Waterwheel Dimension

12/30/2011 7:38 AM

thanks for your guide. I have calculated the area of blade and I got 0.108m^2. However, if i am going to built it, what is the ratio of blade width and blade height. Besides that, is there any ratio for radius of waterwheel with the blade area?

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#9

Re: Waterwheel Dimension

01/02/2012 12:18 AM

1. Check Your calculation. Assuming 50% total efficiency(turbine, gear, generator), A should be about 0.25m^2

2. You can recalculate speed of water to h = head of water (difference of water level - before turbine and after turbine mV^2/2 = m x g x h). 2 m/s ==> h = 0.2m. Water falling from height = 0.2m will have 2m/s. Then go to websites with water turbines, to choose proper turbine, find rotation speed, and what gear You will need (may be).

But this is only for calculation. It is equivalent to case, when water in the pipe is flowing 2m/s, when there is no turbine. After mounting of turbine, turbine with 75% efficiency will slow water speed to about 1m/s, taking 75% of kinetic energy from water. From this 75% after gear and generator may be You will get electrical power equivalent to 50% of water energy.