Author Topic: Pelton wheel and PM generator (Read 25596 times)

BurksFallsMan · « **on:** May 07, 2006, 02:54:52 PM »

I installed the Pelton wheel PM generator by the creek about a month ago. Water is plentiful (approx. 30 - 50 liters/sec. Now I get less than 100 watts and according to Nando should give close to 300 watts.

We thought the case being maybe too small could be restraining the runner, Yesterday tested it with the wheel free ( no cover) and DC amps to battery went from 5.2 to 5.7 or so.

So that is not the problem.

I look at several sites (old pictures) and seems the nozzle is kind of sharply pointed towards the center of the runner.

Anyone had any experiences adjusting the nozzles (I have 2 of 17 millimeters diameter)? ( I mean the angle or anything that can be slowing down the runner).

Following pictures may be fun to look at:

As usual, mounted in site utilizing my "Jury Rigged" method that is only "Temporary" for 10 o 20 years.

Man... I wish I could be having those "pizza"/bear gatherings that you guys have in some areas...... Need to move more people near this area!

Wilson. WFGonzalez2@cs.com

WXYZCIENCE · « **Reply #1 on:** May 07, 2006, 09:30:56 AM »

Air mixing with the water will cause losses in the nozzles. Does the water fall straight down from the runner? Pelton (impulse) turbines under ideal conditions can run as high as 80% efficiency. I see a pressure gauge on the line. What does it run at, valve open and what does it read closed. Your work looks good from this side. Joe

Infinity Steel · « **Reply #2 on:** May 07, 2006, 01:16:37 PM »

I'm no expert on these,but I can see a few things that bug me,from a practical aspect.

1. I'm not sure why you have an open center in the cups. Seems like you have a water blow by of about 50% built in that way. As well as previously mentioned,it's going to foam,decreasing the hydraulic pressure agaisnt what resistant torque you do have.

Think of air as making the water "spongy", as opposed to an even pressure.

An undershot flow that fills as much of the blade spaces against the housing as possible, is going to make the best use of your motive force-gravity. Consider changing the shape and apetures of your nozzle, to see what does that most efficiently. So coming in on a tangent from a 90% up orientation will offer the most force agaisnt your hub. The more of your circumfrence is trapping water before it exits,the better. One third of the total diameter is about max efficiency. Any more, and you begin suffering losses from gravitaional back pressure at the exhaust.
How much more practical head do you have upstream? The farther up your starting elevation into the pipe,the more pressure-balanced by hydraulic force losses from friction and connection turbulence in the pipe. Consider moving the intake farther upstream, if it has enough drop to make it worth it.

Infinity Steel · « **Reply #3 on:** May 07, 2006, 01:18:10 PM »

and I meant to say "circumfrence"' rather than "Radius"

hydrosun · « **Reply #4 on:** May 07, 2006, 02:20:05 PM »

I home made a few pelton systems. I usually had flexible hose or pvc pipe I could move to get the best angle to aim the nozzle. I can't tell from the pictures if your aim may be a little shallow and missing the buckets some of the time. It does look like you have a pretty small nozzle for the size of the buckets. Don Harris told me the small nozzles have too great a percentage of the water hitting the dividing angle and bouncing the wrong way. With small nozzles he would aim it to one side to curl back one side of the buckets.

I don't remember if you posted anything on the rpm of generator, if the rpm drops in half when hooked to the battery. Also how well match the strength of the magnets to the amount of water.? If there isn't any way to adjust the strength the generator is only efficient at one particular setting. So if designed for higher output it would slow it down too much to be at the correct speed to capture the energy of the water.

Just some ideas.

Chris

BurksFallsMan · « **Reply #5 on:** May 07, 2006, 02:26:35 PM »

Joe: There is no air in the water since I purge the lines and also when I look at the water jet coming out (with no wheel in the rig) it seems very solid, crystal clear and cylindrical for quite a few inches. Unless there is microscopic bubbles and I cannot see it.

Also allow me to correct your statement about efficiency. If I recall correctly, in one of the history statements about how Mr. Pelton became very successful was that he entered in a competition regulated by the mining industry (or a mining company) and he won because the others had 60 or 70% efficiency and his design was above 90%.

The quote can be found in the Internet, I do not recall where.

Thanks for you input.

Wilson

WXYZCIENCE · « **Reply #6 on:** May 07, 2006, 02:34:14 PM »

The design of the splitter type pelton wheel was patent in 1889 by, you guess, Lester Pelton. Water hitting the buckets is split and falls straight down losing it's potential energy into the wheel. In early designs the trapped water within the wheel created very poor efficiency. For the best efficiency the buckets should be moving at 1/2 the speed of the impinging water. Joe.

BurksFallsMan · « **Reply #7 on:** May 07, 2006, 02:45:56 PM »

Infinity Steel: Thanks for your input but you got me lost in several areas:

You said:

"An undershot flow that fills as much of the blade spaces against the housing as possible, is going to make the best use of your motive force-gravity. Consider changing the shape and apetures of your nozzle, to see what does that most efficiently. So coming in on a tangent from a 90% up orientation will offer the most force agaisnt your hub. The more of your circumfrence is trapping water before it exits,the better. One third of the total diameter is about max efficiency. Any more, and you begin suffering losses from gravitaional back pressure at the exhaust.

How much more practical head do you have upstream? The farther up your starting elevation into the pipe,the more pressure-balanced by hydraulic force losses from friction and connection turbulence in the pipe. Consider moving the intake farther upstream, if it has enough drop to make it worth it."

Can you elaborate and explain the undershot flow, and the spaces against the housing?

Also what does gravity has to do here? If anything, it would be practically nil considering the 21 feet of water head (approx 8.5 psig at the pelton).

I agree that ideally you want all the particles of water to "hit" as close as possibly to the circumference of the wheel, but practically there are "many particles" competing for that "spot". Some will hit a little lower. the idea I think it is to let the water change direction and in the process loose its kinetic energy.

I do not get the more pressure-balanced by hydraulic forces losses. Can you explain again?

Maybe a sketch with what you believe is the correct or a better setup will be easier to refer to.

Thanks, Wilson

WXYZCIENCE · « **Reply #8 on:** May 07, 2006, 02:49:43 PM »

I agree with your statement about Pelton's efficiency 90% with a 60% work load. If you can achieve that it would be wonderful, and a stream in your back yard is also helpful. Under real conditions and because of my work on steam turbines I tend to always estimate low. Joe.

Nando · « **Reply #9 on:** May 07, 2006, 05:15:23 PM »

Let me respond to the "open center in the cups".

Now this is the standard way of making the Pelton cups or spoons to allow the jet to hit the cup behind for a longer time as compared to the cups without the open center, it gives a better efficiency output.

The Nozzles diameter he has is about 1/3 of the cup diameter, corresponding to the low head he has, if higher head, then the Nozzle diameter may need to be reduced to keep the efficiency up.

He does not have any more room to increase his system head, it is optimum head.

He needs to put flexible 2 inches hoses to each nozzle to be able to aim them to maximum power, he should be getting around 250 + watts minimum and at the Pelton RPM the brushless generator is capable of produce around 400 watts.

I hope he listen to me, I have tried several times, he needs 2 inches hoses with clamps to allow Nozzle aiming with precision.

Nando

Countryboy · « **Reply #10 on:** May 07, 2006, 08:27:40 PM »

Water is plentiful (approx. 30 - 50 liters/sec.

A second? Or a minute?

30-50 liters/sec would yield 300 watts with one meter of head. 30-50 liters/sec is roughly 500-800 gallons per minute.

Peltons are generally for 15 meters of head, or more. If 30-50 liters/sec is accurate, you don't have enough head for a Pelton.

Another thing I noticed is that it appears the pipe feeding the upper nozzle rises. If your nozzle is higher than any part of the headstock, water is being fed to the nozzle by displacement. You want the nozzle to be the lowest point of the pipe.

If the upper nozzle is higher than any part of the headstock, you will get very little performance out of it. You might as well just be running the Pelton with one nozzle, that is on the bottom. (Which would explain why you are getting half the power you expected.)

Also, make sure there are no dips or sags in the headstock. Make sure the water is always running downhill. If the water in the pipe runs downhill, and then has to rise up over a hump, water flow is reduced to displacement flow.

Try turning off the upper nozzle, and see if you have any noticeable effect on performance. That will quickly tell you if your power problem is due the piping to the upper nozzle.

Countryboy · « **Reply #11 on:** May 07, 2006, 08:30:26 PM »

One other thought.

I believe Peltons with multiple nozzles are usually mounted laying horizontal. Since your's is vertical, that may cause you problems getting equal pressure at all nozzles.

domwild · « **Reply #12 on:** May 08, 2006, 12:22:29 AM »

Hi,

Interesting F&P setup. How have you rewired your F&P? Is this an 80S? What sort of electrickery to you have next to the F&P in the picture?

Many questions and so little time!

Slingshot · « **Reply #13 on:** May 08, 2006, 08:34:48 AM »

Slightly off the subject, but where did you get the wheel? Did you build it?

Flux · « **Reply #14 on:** May 08, 2006, 10:16:26 AM »

I see from a previous post that you have 21 ft head available.

Have you measured the head ( pressure gauge) at the entrance to the nozzle.

If the pressure is well up, you can use larger nozzles. I am not sure what your supply pipe can handle without serious loss of head but if you do have 20 ft head and are only making 100w then you can't be using much of your 50L/s.

The nozzles should aim at the divider in the buckets in towards the centre so the water does not pass through the cut out bit of the buckets, that is only to prevent the jet catching the buckets as they come into position.

It looks to me also that the jet is small for the buckets and I would also try moving the jet to one side to feed one bucket direct ( run it as a Turgo)

Do you have the means to alter the speed of the generator to match the nozzle velocity? if not you will not reach maximum power, the velocity is decided by the head and no playing with the nozzles will help if the alternator is too fast.

Very difficult to know what you really have in the way of head, flow and speed.

Flux

BurksFallsMan · « **Reply #15 on:** May 08, 2006, 08:27:32 PM »

CountryBoy:The creek has 30 to 50 liters/sec. (liters per second), but I am using a 4" sewage pipe since I do not need more than 8 to 12 liters per second with the nozzles I have.

The top pipe is going up a little bit but compared with 21 feet is practically zero difference.

The only thing that could happen is we develop a little bit of cavitation in the bend of the 2" pipe, but with 7 psig I do not believe is happening.

Thanks. Wilson

BurksFallsMan · « **Reply #16 on:** May 08, 2006, 08:32:31 PM »

domwild: I did not rewire the F&P, just split the winding to get approx 120 volts AC at approx 380 RPM. Nando knows what F&P I have, I do not.

The gizmo that you see with wires is my "jury rigged" connections on top of the plastic that houses the bearings for th F&P. Just sloppy.

BurksFallsMan · « **Reply #17 on:** May 08, 2006, 08:35:46 PM »

The wheel was courtesy of Nando, I just mounted the wheel and the rest of the monster. The buckets are professionally made. Nando may have more info>

Wilson

Countryboy · « **Reply #18 on:** May 08, 2006, 08:36:39 PM »

Hi Wilson,

You have half the head you should have if you want to run a Pelton. They like a minimum of 15 meters, or 45-50 feet.

Try a Banki instead of the Pelton.

It may not seem like much, but if the pipe goes upwards, water flow is reduced to displacement. To experiment, allow water to gravity flow downwards through a section of garden hose that is perfectly straight. Then, turn the bottom of the hose into a J - even though it doesn't seem like much of a bend, you will see a drastic reduction in flow.

hydrosun · « **Reply #19 on:** May 10, 2006, 07:46:23 PM »

I don't understand. You say you're running 8 to 12 liters per second. I translate that as 2 to 3 gallons second. Or 120 to 180 gallons per minute. Looking at a discharge table for nozzles I get about 90 gallons per minute for a one inch nozzle at 20 feet head. The one picture of the nozzle you're using show about a 1/4 inch opening. Did you cut off the end to make a larger opening? That would explain Nando's remark about the nozzle being 1/3 the size of the buckets. If that is the size of nozzle I take back my remark about aiming the nozzle to one side of the splitter. So the calculation is 120 gpm times 21 feet divided by 10 to get 240 watts at 50% efficiency. About the same that Nando calculates. How did you determine how to aim the nozzles? I think Harris looks through the nozzles before they are connected to piping to aim and then lock them in place. The other option is to have them flexible to be able to move the flow of water until the highest output is achieved and then locking them in place.

How long is the pipe and do you have a pressure gage in place? A restriction at the intake screen or a high point in the pipe with a pocket of air could cause a loss of pressure when the water is flowing. How did you determine the 21 feet of head? I sometime use a pressure gage to determine the head but know that not all gages are really accurate. A faulty gage could skew the numbers expected. I seem to remember that you had another set up with a banki turbine which put out about 100 watts. How much water did that setup use? Can you open up the nozzle more to add more water to the pelton? Or are you at the limit? At 120 gpm you'd lose almost a foot head in 100 feet of 4 inch pipe. 200 gpm would lose 2 feet head for 100 feet pipe. I 'll have to go back and see how long your pipe is.

Chris

crossk · « **Reply #20 on:** November 26, 2006, 03:27:45 AM »

Hey Nando,

Would you mind saying where the wheel came from? Thanks

Crossk

crossk · « **Reply #21 on:** November 26, 2006, 03:29:49 AM »

Hey Nando, would you mind saying where the wheel came from? thanks

Crossk

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Author Topic: Pelton wheel and PM generator (Read 25596 times)