Author Topic: 5kw Poncelet Wheel Project  (Read 72809 times)

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skid

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Re: 5kw Poncelet Wheel Project
« Reply #243 on: December 02, 2017, 07:46:54 PM »
Could torque from the waterflow be twisting on the bearing, creating excessive side loads?

The bearing loading from the wheel is evenly balanced, plus the bearings are quite large for the application. The axial loading is minimal, while the radial load is low and low speed. The inboard bearing does have a higher load imposed by the belts, but compared to the generator bearing which so far has had no issues, is at least twice the size. The generator bearing is a single deep groove ball bearing while the waterwheel bearing is a double spherical roller bearing. From Wikepedia - Most spherical roller bearings are designed with two rows of rollers, allowing them to take very heavy radial loads and heavy axial loads.

Good to hear.
And you've backed off the belt tension, too, I guess?

Belt tension is what I would consider to be minimal considering the high torque generated by the wheel. I've always had it on the loose side so when the wheel was shuddering I thought it was belt slippage.

Before the wheel was always speeding up and slowing down, now it is running at a steady but noticeably slower rpm. The inverter is now allowing it to load up properly now it appears. I'll keep a close eye on it for now...

hiker

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Re: 5kw Poncelet Wheel Project
« Reply #244 on: December 02, 2017, 08:38:43 PM »
With all that high torque...you could speed things up a bit...?
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skid

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Re: 5kw Poncelet Wheel Project
« Reply #245 on: December 02, 2017, 09:02:09 PM »
With all that high torque...you could speed things up a bit...?

I don't think it would make any difference power-wise. The inverter loads it down to make max generation. To make more power I need to create more blade area. I'm looking into that.

One thing I've noticed is that there is a bit of inefficiency from blade slap from the back of the blades hitting the water. It sounds like a bass drum. I'm looking into extending the blades another 2 feet in diameter, and widening the blades as well. I mentioned to my CAD buddy to see if the blade extensions can be shaped in a V as well to create even more surface area and to reduce blade slap as well.

george65

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Re: 5kw Poncelet Wheel Project
« Reply #246 on: December 03, 2017, 03:02:20 AM »

There is a lot written about belt tension but a mate who worked in industrial power transmission had a rule with it..... Only has to be tight enough not to slip and if it's obviously too tight, you need more belts so you can have them relatively slack.

Always worked for me. I don't like tight belts because of the loads and friction they impose. When pulleys and belts are in good nick and under stressed for the job, you can run them relatively loose and they still transmit the power fine.

MattM

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Re: 5kw Poncelet Wheel Project
« Reply #247 on: December 03, 2017, 05:39:49 PM »
I know this is counter-intuitive, but what if you traded out the rigid buckets for flexible bands?  Kind of a mudflap supported on the sides.  As it strikes into the water it gives, but as it submerges in deeper water shifts pressure to the backside.  It should be much quieter.

george65

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Re: 5kw Poncelet Wheel Project
« Reply #248 on: December 04, 2017, 04:09:38 AM »

No doubt it's been done and there is data somewhere but the above suggestion gives me a thought....

What if the blades were hinged or pivoted?

They would enter the water on the thin edge, push back on stops when the water is driving them  but would probably pivot and pull out the water more cleanly instead of trying to lift it at an angle as they withdraw.  I don't think it would be quieter, probably clank and even squeak a bit  but possibly reduce some of the drag as the blade would I think lift out the water on it's edge rather than having water running off the back as resistance.

Wonder what such a wheel is called and how it is efficiency wise?

Mary B

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Re: 5kw Poncelet Wheel Project
« Reply #249 on: December 04, 2017, 04:11:26 PM »
More moving parts = more points of failure... KISS principle comes to mind...

keithturtle

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Re: 5kw Poncelet Wheel Project
« Reply #250 on: December 05, 2017, 12:55:50 AM »
I thought extending the inner lip of the bucket inward with a curl, more like the Poncelet design, to capture more of the energy.  Once the flow  "hits the wall" the  velocity will play a bigger role

Maybe.

Thanks for sharing the saga

Turtle
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skid

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Re: 5kw Poncelet Wheel Project
« Reply #251 on: December 05, 2017, 02:03:02 PM »
I thought extending the inner lip of the bucket inward with a curl, more like the Poncelet design, to capture more of the energy.  Once the flow  "hits the wall" the  velocity will play a bigger role

Longer blades extending out further will do the same thing I'm hoping. If after adding longer blades and water still pours out the middle of the wheel I will seal the blades off as there is definitely lost energy there.

I was carefully analyzing the wheel's operation yesterday and noticed that the blade slap is actually the water hitting the front of the blade, not the rear. Sounds like the bass drum in a teenagers car stereo. My neighbor says he can hear it when he is near the river.

keithturtle

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Re: 5kw Poncelet Wheel Project
« Reply #252 on: December 05, 2017, 08:10:42 PM »
My neighbor says he can hear it when he is near the river.

That's not a good omen.  Maybe you'll be successful where others have failed in the acoustic dampening arena

https://www.enoisecontrol.com/noise-canceling/

At least it is rythmic, should make it easier

Approach it with earnestness

Turtle
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MattM

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Re: 5kw Poncelet Wheel Project
« Reply #253 on: December 05, 2017, 09:41:33 PM »
You can only grab so much energy.  The issue doesn't sound like how much energy, but rather what happens to the excess energy.  It sounds like you displace so much water it is audibly significant.  No matter how the bucket is shaped the laws of physics prevents any improvements to capturing the energy.  I'm thinking you want a solution that allows that other 33% you cannot capture to quietly continue downstream.  You want the rig to move with the flow displacing a minimal amount of water.  My intuition leans toward allowing 33% of the water to pass through undisturbed.

joestue

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Re: 5kw Poncelet Wheel Project
« Reply #254 on: December 05, 2017, 11:41:00 PM »
can you make the buckets helical?

MattM

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Re: 5kw Poncelet Wheel Project
« Reply #255 on: December 06, 2017, 04:59:31 AM »
That would be like a massive redesign.  He's put a ton of effort into this thing and it's more or less an exercise in aesthetics.  I was thinking less buckets or sideways, but again a major change.  His new lip might actually bite the water quieter.  How would somebody manufacture a helical prop to fit his rig?
« Last Edit: December 06, 2017, 05:36:18 AM by MattM »

joestue

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Re: 5kw Poncelet Wheel Project
« Reply #256 on: December 06, 2017, 11:17:02 AM »
Doesnt have to be a true helix.

Mary B

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Re: 5kw Poncelet Wheel Project
« Reply #257 on: December 06, 2017, 04:52:07 PM »
K.I.S.S. !!!

Minor bucket mods yes, major redesign? That could take a year or more.

SparWeb

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Re: 5kw Poncelet Wheel Project
« Reply #258 on: December 06, 2017, 06:50:02 PM »
Gotta take Mary's side here.  Skid is already doing well already.  No sense being greedy.
A functional energy-producing system is more important than tweaks that might (or might not!) improve its performance.

Skid, if you want to chase the noise and splashing problem any more, might I suggest something like a go-pro camera attached to a spoke pointed at the paddles.  Then you would see the whole water immersion process from the paddle's perspective and know for sure what's causing the slap, and if you should do anything about it.
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MattM

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Re: 5kw Poncelet Wheel Project
« Reply #259 on: December 06, 2017, 06:56:48 PM »
Parachutes with a hole in the apex are more stable than fully enclosed parasols.  They form a targeted amount of drag rather than attempting a full stop of the air.  I wonder if the solution is allowing water to pass through easier as the paddle strikes the top edge of the water.

Frank S

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Re: 5kw Poncelet Wheel Project
« Reply #260 on: December 08, 2017, 08:09:10 PM »
Almost sounds like a cavitation splash
https://www.youtube.com/watch?v=OPfjoAQxvcQ
 just adding an inner shield may do some to quieten the blades at the same time improve output
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clockmanFRA

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Re: 5kw Poncelet Wheel Project
« Reply #261 on: December 09, 2017, 09:25:20 AM »
I thought this might help.

Pics of a local undershot wheel, this stopped working in 1960. But being in France nothing gets moved about much.

Everything is possible, just give me time.

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