Author Topic: hydro experiment (Read 7747 times)

windspeed · « **on:** March 29, 2009, 08:55:23 PM »

our group in the west of Ireland have started to build a low head banki

we have .5 mtr of head and flow 33 ltr per sec average

we are building the prototype from ply and pipe slotted in a holding disc with a full backing disc 9" dia ..this is backed by a 6" saw blade ..........see pics

the axle is a 16 mm threaded bar with 2 ebay pillow block bearings either side

next task is the mounting frame which will be bolted onto the 3ft high x 6ft wide wooden dam

then the nozzle any ideas or constructive criticism is appreciated

Windspeed

12AX7 · « **Reply #1 on:** March 29, 2009, 03:39:53 PM »

Hello..

I've nothing solid to base this on but.. wouldn't opening the sides give the water a easier way of flowing "out" of your wheel? Other wise a lot of it's energy be spent "throwing" the water out of it?

Sometime in the future I hope to build and install a waterwheel/paddle wheel in a river, looking forward to your progress!

Mark

ax7

Phssthpok · « **Reply #2 on:** March 29, 2009, 07:24:13 PM »

Banki Turbines are designed to extract power from the water TWICE as it passes through the 'barrel'.

http://en.wikipedia.org/wiki/File:Banki.svg

scottsAI · « **Reply #3 on:** March 29, 2009, 08:03:00 PM »

Windspeed,

Nice work!

From my readings, the two most common errors in building a Banki are:

Blades need to have a knife edge, maybe not knife sharp. No square edges. Helps the water flow around the blades better. Hard to tell from pictures, looks thin or already had an edge.

Nozzle must have a water feed Much larger than the nozzle area. Very important full head pressure exist just before the nozzle opening. The job of the nozzle is to convert potential energy to kinetic energy (speed up the water to squirt out).

Turbine is a low power unit, after testing, you plan to replace the plywood?

Consider PCV pipe, should go together easily.

Consider smaller dia. With your head maybe 6 inches dia. would do?

Have fun,

Scott.

Jon Miller · « **Reply #4 on:** March 30, 2009, 03:20:33 AM »

Hi there,

Whats the plan for the larger blower i can see in the second picture, i have one and would like to know if any one has had good results?

Regards

thirteen · « **Reply #5 on:** March 30, 2009, 09:04:26 AM »

seal the plywood good it will love to absorbe your water then split. I don't know if you are in a cold climate, I was thinking of freezing water. But it is fine for your experiment. Maybe you could experiment by using air to test it. You could check the spec. on the bearings. If you have one that can use a light oil or light duty grease the drag will be less on your bearings. They are more $$$ but they do make plastic bearings that use little maintenance. You can get a grease gun extention hose that fits the bearing housing where the grease zert is. It may keep you dry or make it easier to service. Where the fins are you might put a band around them so they won't slide out. Just some ideas

Flux · « **Reply #6 on:** March 30, 2009, 11:07:39 AM »

Yes Scott I agree, that is a fair sized rotor and will need a huge feed to supply a nozzle of that width even if it only spans one blade. If there is any significant head I doubt that the blades would support the force on them.

Flux

pepa · « **Reply #7 on:** March 30, 2009, 11:07:40 AM »

jon m check dan b's old projects file, i seen a write up on one a while back with pictures. pepa

windspeed · « **Reply #8 on:** March 30, 2009, 01:48:46 PM »

Scott

thanks for your comments

sharpening the edge is next, probably should have done it before assembly

I will post photo of the nozzle soon the depth of it will be ajustable by either a slidng or pivoting metal sheet

the ply is temporary but we intend to stand the turbine on end in varnish starting with a thinned down mix and another thicker mix after

do you mean pvc pipe for the vanes......... I don't think at 17" it would be strong enough as Flux said

I agree a small diameter would be a better match

Jon no plan at this time, open to suggestions

yes Thirteen that is a good idea I hope it won't be a problem as we glued the outside supporting disc to the inner one where the vanes came through and I expect the varnish will soak in around the arcs which we cut for the vanes

the bearing have a little drag but will do for now

I would be disapointed if it didn't produce 75 watts

thanks again

Windspeed

hiker · « **Reply #9 on:** March 31, 2009, 01:15:13 AM »

check this out.............

http://www.otherpower.com/otherpower_hydro.html

scottsAI · « **Reply #10 on:** March 31, 2009, 05:28:05 PM »

Windspeed,

PVC for everything, forces for 200w should be within its capability.

If worried, add a middle disk to stabilize it. PVC is cheap and easy to work.

Force of the water is along the whole blade, not just the center.

33l/s is a lot of water, 0.5m head not much pressure.

Nozzle thicker than couple blades spacing is OK.

Have fun,

Scott.

windspeed · « **Reply #11 on:** April 01, 2009, 02:27:45 AM »

Hi Scott

probably be fine with a central support disc if it would not interfere with flow

from what would you make the discs and how would you attach the pvc.

do you think the pvc would become brittle in sun

do you think it could make 200 watts

Windspeed

scottsAI · « **Reply #12 on:** April 01, 2009, 02:37:40 PM »

Windspeed,

If your serious about PVC, tell me the dimensions of the Banki, materials your considering using and I will figure out the forces, should be able to tell if OK.

200w is your target? What are the potential power numbers from the water flow?

Center Disk

Disk in center on the inside edges of blades should stiffen it up without interfering with water flow. You know to keep the center area clear (no shaft) Disk is aligned with water flow, should not be blocking any serious amount assuming you even needed it.

Use a cover over the turbine to block UV.

Have fun,

Scott.

windspeed · « **Reply #13 on:** April 02, 2009, 01:01:26 PM »

Hi Scott

if you look at the pictures on this page the water doesn't touch the axle

I was banking on this

http://www.ossberger.de/cms/en/hydro/the-ossberger-turbine/

As for the demensions....the turbine is 17" wide and 9" dia ..any smaller would be difficult to fabricate even though I think it would be better

the flow could be over 60 ltrs per sec

and the head could rise to over .75 mtrs

Windspeed

scottsAI · « **Reply #14 on:** April 02, 2009, 08:12:53 PM »

Windspeed,

Considering the volume of water, 9 inch dia seems reasonable.

Smaller dia only gets you a higher rotational speed.

Using this power calculator:

http://www.reuk.co.uk/Calculation-of-Hydro-Power.htm

Power = 441w assuming: 0.75m and 60l/s, the force you must deal with.

Not the power you will get out, With 20l/s 75w looks possible.

Force on blades:

Assumptions RPM = 250, seems a middle of the road RPM.

From: http://en.wikiversity.org/wiki/Torque_and_angular_acceleration

Power = Torque * angular speed = Torque * 2pi * RPM / 60

Torque = 60 * 441 / (2pi * 250) = 16.8 Nm (Please check my math).

We know Torque is Force times distance lever.

Now divide by Banki's radius to get Force in N placed on the blades!

Divide by length to get force per unit area. (Not needed)

Torque = Force * Radius

Force = 16.8Nm / 0.1143m = 147.4 N.

Since I know English system 33.14 lbs force over the length of the blades.

Using PVC you might consider center support? What do you think?

I would cut a blade and put 16lbs on the center with ends supported, look at the deflection, if your OK with it then go with it! The water may be on more than one blade at a time, so stack how ever many blades to do the test.

Using 20l/s don't think center support is needed using PVC blades.

Have fun,

Scott.

windspeed · « **Reply #15 on:** April 03, 2009, 09:55:46 AM »

Scott

Did you look at the Ossenberger site do you think we will be able to keep the water away from the axle

Windspeed

scottsAI · « **Reply #16 on:** April 03, 2009, 03:27:11 PM »

Windspeed,

Ossenberger interesting web.

Several Banki design guides show similar water flow path, some say water flows through the center and not to use center shaft. Must depend on two things, how thick the water flow is and the angle of the blades?

If the flow is one blade wide, you may be OK, several wide some water must pass through the center?

Any chance you can test the water flow through your turbine?

Nice thing about Banki, is a 1 inch nozzle should work the same as a full length nozzle.

Have fun,

Scott.

windspeed · « **Reply #17 on:** April 04, 2009, 01:43:21 PM »

We will be installing the turbine in the river tomorrow ...checking flow at the nozzle

and through the turbine

any ideas on a generator for this 50 to 200 watts expected

Thanks

Windspeed

spinningmagnets · « **Reply #18 on:** April 04, 2009, 05:34:09 PM »

What voltage do you hope for?

Much will depend on RPM's and torque. If you have enough torque, you might consider a cheap and easy experiment by adding the toothed timing belt and 2:1 pulleys from a wrecked car.

"If" the higher RPM's help, it may mean having to use a smaller gen (less amps produced?) but the higher voltage from the higher RPM's may make it worthwhile in spite of added complexity and fiction.

Before steam, many of industries used a wide breastshot wheel with high torque (DuPont). If your Banki experiment works well, but "almost" has enough torque to spin a 2:1 ratio gear-up, do you have enough flow to make it wider?

Just an idea...

windspeed · « **Reply #19 on:** April 05, 2009, 03:19:41 AM »

we are aiming for 24 v

I am trying to steer clear of gearing for now....... at times the flow would be ok for a geared output but I could see it not even starting to produce at average flow and below... not sure about making it wider yet ......I don't know how much water will actually flow through the wheel

how could I measure torque on this.

thanks

Windspeed

spinningmagnets · « **Reply #20 on:** April 05, 2009, 10:18:13 AM »

I have not owned a hydro syatem yet, so don't spend any money or time based on anything I say, but I very much desire a hydro-site for my retirement, so I am following your posts closely for my "hydro file".

Whether you are making a PMA from scratch or adapting a PMM, once you apply a load to your Banki, it may slow down a bit, which throws off your voltage generated calculations. Then you would have to use a smaller load (smaller gen?) or a wider wheel to add torque. Of course, only if you had enough flow to work on the extra width of the blades.

If I understand correctly, low battery charging can be as high as 10% over pack voltage, so for a 24V pack you are aiming for about 28 volts? Apply "some" small friction load to the output shaft, and then measure RPM's, then you can find or make a PMA to make 28 volts at that RPM.

A large water wheel has a rim speed of about 80% of the water flow speed, but if your Banki has the flow choked down to create a "jet" effect (like a Pelton?) I couldn't guess how it would effect RPM's, or even RPM's under load.

If your gen is too small, you are missing out on Watts that are just flowing through you fingers, but too big and it will bog down the water turbine and drop RPM's and voltage output. The turbine should use 80% of your water flow, and the gen should be sized as big as possible, but not so big as to bog down and slow the turbine.

The wonderful thing about hydro is that once you get it dialled in, the output can be fairly steady 24 hours/day. You can even increase or divert flow to affect RPM's/Volts, such as an equalizing charge or lowering input amps as you near a full battery.

Don't be concerned about using wood. You may end up making several changes to the diameter and width before you are satisfied. If it works well, you can make a better non-wood final version before the first freeze. The wood parts can be a pattern for you.

If this works out well, you might size one Banki for minimum annual flows. Then you might have a second or third one to take advantage of the heavy spring flows with snow-melt and rain.

Best of luck!

windspeed · « **Reply #21 on:** April 05, 2009, 02:45:20 PM »

We installed the turbine today without the generator

We found our nozzle was not adjustable enough so back to the drawing board

so we ran it without the nozzle.... guesing the rpm to be 150 but good torque

no actual measurements here either

cosidering a 2 or 3 to 1 geared drive.... low rpm but good torque

maybe a cordless drill with gears would be a good match

I think 60% of the water was going through the turbine

maybe the nozzle correctly set up would feed more water through the blades directing it towards the centre of the turbine instead of tangentaly and loosing it behind it

(this is a verticle feed )

not sure yet but this could possibly be made wider maybe 20"

"If your gen is too small, you are missing out on Watts that are just flowing through you fingers, but too big and it will bog down the water turbine and drop RPM's and voltage output. The turbine should use 80% of your water flow, and the gen should be sized as big as possible, but not so big as to bog down and slow the turbine."

I think I could I put resistance in the line to prevent bogging down

and get near to 80% of water flow

"The wonderful thing about hydro is that once you get it dialled in, the output can be fairly steady 24 hours/day. You can even increase or divert flow to affect RPM's/Volts, such as an equalizing charge or lowering input amps as you near a full battery."

She will be running at max 24/7

"Don't be concerned about using wood. You may end up making several changes to the diameter and width before you are satisfied. If it works well, you can make a better non-wood final version before the first freeze. The wood parts can be a pattern for you."

no freeze here..steel or pvc would be our next materials of choice

if this works out well, you might size one Banki for minimum annual flows. Then you might have a second or third one to take advantage of the heavy spring flows with snow-melt and rain

just rain

thanks for your comments

News:

Author Topic: hydro experiment (Read 7747 times)