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Impulse Steam Turbine
By WXYZCIENCE, Section Mechanical Posted on Thu Mar 1st, 2007 at 05:25:09 AM MST
Next Model #8

These are the first pictures of my new Stream Turbine. The new model is eight inches in diameter and is cut from 3/8" plate stainless steel 308. My tests on a 4" impulse steam last year were very good. I achieved 100 watts at 40 psi of steam.

Stainless steel is very hard to machine and this rough cut has over thirty hours into the blades and hub. There are sixty teeth on the rotor and a ring will cover the teeth producing channels for the steam. A close up shows the channels for the steam input. The channel narrows as it reaches the center compressing the expanding steam and transferring the energy into the rotor. The reduction in the velocity of the steam is about half.

The blades were cut on my lathe using a 4 3/4" bimetal circle cutter. Pictured here is the 4" turbine blade being cut last year.

Eight inches is the maximum that I could cut on my indexer. The depth of cut was 1/4" and the bimetal cutter cut 120 cuts and remained sharp. This last picture is to compare the two units.

I want to design an alternator for this unit after initial rpm test are done on the rotor which I expect to operate at around 12000 rpm. I have estimated 500 watts from this unit and 80000 btu of co-generated heat. This unit gets it's steam from a coil tube boiler that I will post pictures of later. The boiler will be fired with wood and be around 3BHP (Boiler Horse Power) The waste steam will be condensed and the heat will be used to heat a green house. Hopefully this year.
Joseph.

Impulse Steam Turbine | 25 comments (25 topical, 0 editorial)

Re: Impulse Steam Turbine (3.00 / 0) (#1)
by nanotech (darrin(dot)moore(at)gmail(dot)com) on Wed Feb 28th, 2007 at 11:25:10 PM MST
(User Info)

WOW!! All I can say is wow!!

Some heavy duty craftsmanship there.

12,000 RPM? Heh, going to need one hell of a reduction gear I think!! And 80,000 BTU of heat is going to heat one BIG greenhouse!! ;)
__________________________________________
My ship finally came in, but it was the Kobayashi Maru!

Re: Impulse Steam Turbine (3.00 / 0) (#10)
by Ungrounded Lightning Rod on Fri Mar 2nd, 2007 at 12:37:13 PM MST
(User Info)

Naw. Instead it's going to enable a very SMALL alternator. B-)

A two-pole will be 200 Hz, a 4-pole 400 Hz (convenient for surplus transformers and electronics B-) ), and so on. The high RPM can be traded for small rotor size, weaker magnetic field, or higher volts-per turn (which means more power per unit current and can be traded for fewer turns of thicker wire if you want a low voltage).

Sweet.

[ Parent ]

Micro ORC Steam Turbine (3.00 / 0) (#25)
by spinningmagnets (velmis1450bc(at)aol(dot)com) on Tue Sep 9th, 2008 at 07:19:05 PM MST
(User Info)

There's an increasing use of Organic-Rankine-Cycle (ORC) which is a steam tubine that uses Freon or some similar substance that boils at a lower temp than pressurized water.

There are increasing protests against new coal and nuclear plants. Since ORC can use geo-thermal or solar heat, the political benefits may far outweigh the drawbacks.

"...The organic Rankine cycle designed for the U.S. Department of Energy's Small Communities Project by Barber-Nichols Engineering is designed to be placed at the focus of a single solar parabolic dish concentrator.

It is designed to produce 26 kW of shaft power with a peak operating temperature of 400ºC (752ºF). The working fluid here is toluene.

In order to enhance the efficiency of such a small system, the turbine, pump, and alternator are incorporated on the same shaft as pictured. This concept also eliminates a dynamic shaft seal, enhancing its service life.

This single-stage, axial-flow turbine spins at 60,000 rpm and has a mean blade diameter of 12.5 cm (5 inches). This engine has a thermal efficiency of 24 percent which is 45 percent of the ideal Carnot efficiency..."

http://www.powerfromthesun.net/chapter12/Chapter12new.htm

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#2)
by ruddycrazy on Thu Mar 1st, 2007 at 01:19:24 AM MST
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Hiya Joe,
Eh mate here's question for ya how would a crown wheel off a worm drive go with steam? being brass/bronze it will be impervious to water and with sealed deep groove ball bearing speed wouldn't be a problem. It's just as I overhaul industrial gearbox's I come across then all the time and have been wondering ever since I saw your first one. I have some 0.011" carbide drill so I could make some hardened nozzles for the jets but I'd like a second opnion before I start.

Cheers Bryan :{)

Re: Impulse Steam Turbine (3.00 / 0) (#5)
by WXYZCIENCE on Thu Mar 1st, 2007 at 02:47:42 PM MST
(User Info)

Brian, I have seen the bronze gears that you are talking about. Your blade pitch would be very high. You need to mount the disk on a suitable arbor and test it with 100 lbs of air pressure through a test nozzle. It might make a fair reaction type turbine blade. Because the channels are symmetrical you will lose a lot of power. Steam expands as it leaves the nozzle.

You must either compress the steam through the channel or change it's direction to remove the energy stored in the steam. I have had good success using the impulse method for a single stage turbines.

Thanks for your interest. Joseph

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#3)
by scottsAI (user name at eml dot cc) on Thu Mar 1st, 2007 at 11:47:52 AM MST
(User Info)

Hello WXYZCIENCE,

Tesla Boundary Layer Turbine
Have you looked into:
http://phoenixnavigation.com/ptbc/ptbcproducts.htm
Another link:
http://www.stanford.edu/~hydrobay/lookat/tt.html

Use one for the steam another smaller one to pump up the condensate back into boiler. On one shaft.

Nice work on your current turbine.
I have never built the Tesla turbine, only read about it.
Anybody built one?
Have fun,
Scott..

Re: Impulse Steam Turbine (3.00 / 0) (#12)
by Ungrounded Lightning Rod on Fri Mar 2nd, 2007 at 07:32:45 PM MST
(User Info)

I've thought about using a tesla turbine/compressor/alternator/startup-motor on a shaft with a parabolic trough solar concentrator and a pipe-in-pipe heat exchanger for a solar-powered gas-turbine system. The high RPM would make for a very small motor/genny.

With a trough it would not be as efficient as with a point-focus with tracking system, where the higher temperature of the hot end means the carnot cycle penalty is far lower. But virtually all the waste heat is still available for capture as water or building heating, and a single moving part is hard to beat.

But I'm not sure how efficient a practical tesla turbine is. (Too much inefficiency and you don't have anything left after pressurizing the input air.) Meanwhile, balance and long-life bearings for its hysterical speed (without continuous lubrication and lubricant spills into the working fluid) might be problematic.

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#14)
by scottsAI (user name at eml dot cc) on Sat Mar 3rd, 2007 at 09:10:13 AM MST
(User Info)

Hello Ungrounded Lightning Rod,

The whole claim to fame is the efficiency.
One Tesla turbine has many stages built in one turbine blade.
As the gas enters at the outer edge of the disk, imparting energy to the disk, continues expanding as it rotates to the center and exits.

The final rotational speed will be dependent on the dia of the turbine.
So make it bigger! I had a turbo charger in my car, claims of 150k RPM and higher. Lasted for years.

What WXYZCIENCE has made is a single stage turbine. (Nice job)
The turbine I used in the military had many stages to recover more of the energy.

I was hoping to find someone that has built a Tesla turbine, I have read quite a bit about it.
Have fun,
Scott.

[ Parent ]

Tube Boiler (3.00 / 0) (#4)
by WXYZCIENCE on Thu Mar 1st, 2007 at 02:22:27 PM MST
(User Info)

Eighty feet of 3/4 inch pipe are coiled to form the guts to the steam generator.

The tubes will be mounted into an old automotive propane tank next month.
Joseph.

Re: Tube Boiler (3.00 / 0) (#7)
by SparWeb (sparweb at ANTISPAM_hotmail_com) on Thu Mar 1st, 2007 at 11:22:45 PM MST
(User Info)

16" coil of 3/4" steel pipe - schedule 80! You found that coil as a unit right? Is that coil an oil-field left-over?

If you "invented" something to coil up that tube, I am very curious to know about that! It would take some serious torque for a machine to do that, even heated up! Does it have some advantage over, for example, schedule 20 copper pipe, that may not be obvious? The copper would transfer heat more efficiently.

About the steam impeller: Were you constrained to use the size of cutter you did? A smaller diameter of cutter might have allowed a less-sharp apex in the throat of the vanes. Of course, it looks like it will work well the way it is!

Your inventions are fun to see. Thanks.
Steven Fahey
[ Parent ]

Re: Tube Boiler (3.00 / 0) (#8)
by WXYZCIENCE on Fri Mar 2nd, 2007 at 01:25:01 AM MST
(User Info)

Steven, the coils are made from 21' lengths of pipe then welded together. The machine we built coils up to 1" easily. Have not tried any larger. We do not heat the pipe. After a coil is made it is then backed off one turn to remove the spring force. It then slides of of the form easily. Steel holds the heat longer and I can control the steam better. If the unit runs dry there is no ill effect to the steel coil. Unlike copper you get too much copper oxide inside the coils. Most copper tube boilers that are gas fired have shut downs to stop flashing. Wood fired can't be shut down that fast.
On my 4" unit I used a 3-3/4" cutter. On this 8" unit I used a 4-3/4" cutter.
Joseph.

[ Parent ]

Re: Tube Boiler (3.00 / 0) (#23)
by jht1057 (jht1057(at)yahoo(dot)com) on Tue Apr 24th, 2007 at 06:36:49 AM MST
(User Info)

To say I am impressed is so lacking, What your doing is freaking awsome!!

I play with live steam train engines on a scale of 1" = 1' , Pullman engines are a tube coil design and you are right copper is not the material. I would be really interested in the method and tooling you are using to do your 1" steel coils. Could you post or send some information on your coil roller??

I found this looking for impeller designs, there seems to be a need for small to scale generators for lighting on the steam engines I build.

Jim

"Should you allow someone to tell you it can't be done, it won't be"
[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#6)
by willib (willibur at comcast dot net) on Thu Mar 1st, 2007 at 08:15:56 PM MST
(User Info) http://www.njwind.com/webcam.html#

At 12000 rpm you wont need many turns per coil ,thats for sure.
maybe three or four? ten at the outside..
it might be hard keeping the mags in place , or balanced ?
which type of alt are you planning for this? RACA ? Axial
are you planning any speed reduction.

Nice work on the turbine,the plates line up perfectly..
so many questions , so little time. :)
Carpe Ventum (seize the wind)

Re: Impulse Steam Turbine (3.00 / 0) (#9)
by WXYZCIENCE on Fri Mar 2nd, 2007 at 01:34:21 AM MST
(User Info)

Willib, I am going to try an axial six pole three phase unit. It will have to be very well balanced because I want to run it at very high rpm. I will post pictures of the alternator soon.
Joseph.

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#11)
by ghurd on Fri Mar 2nd, 2007 at 05:24:07 PM MST
(User Info)

The local dudes won't hardly drill a hoile for me. :-(

Re: Impulse Steam Turbine (3.00 / 0) (#13)
by blimpyway on Sat Mar 3rd, 2007 at 04:45:06 AM MST
(User Info)

Hi WXYZCIENCE,

How much steam per minute at 40psi the 4" turbine needed to make 100 watts?

Thanks,
Cezar

Re: Impulse Steam Turbine (3.00 / 0) (#15)
by WXYZCIENCE on Sat Mar 3rd, 2007 at 08:26:24 PM MST
(User Info)

Cezar, through a 1/4" nozzle the boiler will hold a steady 40psi. I have not got an exact figure of lbs per minute. With the new tube boiler I should get better figures of steam volume.
Joseph.

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#16)
by blimpyway on Fri Mar 9th, 2007 at 01:34:17 PM MST
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Thanks Joseph,

Still I'm a little confused here http://www.fieldlines.com/story/2006/4/22/201245/472#7
you say the nozzle is 1/16 inch, not 1/4, which is 16 times smaller.

Here are my semi-random thoughts.. not sure they-re very acurate:

At a rough aproximation, to keep steam exiting through a 1/16 inch at 40psi would need 2000-3000 watts of heat, yielding (at 100 watts mechanical) 3-5% thermal efficiency. The 1/4 inch nozzle would require 16 times more heat to produce 100 watts.

------

Have you considered just adding more steam (using the big boiler & several nozzles) to the small (4") wheel and double its RPM?

------

By using a condenser the nozzle speed and efficiency should increase significantly.
Instead of expanding 2.5-3 times, the steam could expand more than 10 times.
A condenser creates vacuum so it also decreases a lot the aerodynamic friction loss at such high RPM.

------

I think increasing the turbine's peripheric velocity will improve efficiency too.
A 10cm wheel running at 12000 rpm has a top velocity of ~60 m/sec.
At 40psi the expanding steam reaches 900-1000m/sec.
Spinning the turbine closer to half the steam exit velocity should extract more mechanical power from it.

Turn it as fast as it doesnt breaks.

Regards,
cezar

Re: Impulse Steam Turbine (3.00 / 0) (#17)
by WXYZCIENCE on Fri Mar 9th, 2007 at 02:05:25 PM MST
(User Info)

cezar, you are correct about the amount of heat required to produce that amount of steam. My first boiler can be fired over 60000 btu. I don't like to run the boilers that hot. This next boiler will be able to give me more steam but I will have to wait and see how good it will actually work.
At 40psi the expanding steam reaches 900-1000m/sec.
This is interesting I will have to research more.
If I were an engineer, probably would have quit long time ago.Thanks for you input
Joseph.

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#18)
by blimpyway on Fri Mar 9th, 2007 at 05:17:27 PM MST
(User Info)

Seek for more info about the Gustav de Laval impulse turbine, it is one of the oldest steam turbine designs, single stage impulse turbine, much like yours.

I found a very poor drawing on 3rd page into this document: http://files.asme.org/ASMEORG/Communities/History/Landmarks/5527.pdf

What is interesting it ran at 20000-30000 RPM, and having larger diameters, then its "tip speed" was much higher than in your tests.
It had multiple nozzles and the cross section of the channels between blades was constant, so the steam flows through it at constant pressure.

You should also see the choked nozzles Laval invented for its turbine, their design was used in later rocket engine nozzles: http://en.wikipedia.org/wiki/De_Laval_nozzle

At that page is also a formula to compute the steam's (or any other gas) exit velocity through a de Laval nozzle. (I made a rough estimation, I was not using this formula)

-------
At its time the de Laval turbine was considered having low efficiency, but part of this should be blamed on its unusually high rpm, and the gears used to reduce it at useable values for the epoch's generators.

------

In this range of low power and very high rpm you may try to use a brushless electric motor designed for high speed propellers or impellers for large model airplanes.

-------

cezar

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#19)
by blimpyway on Fri Mar 9th, 2007 at 05:40:31 PM MST
(User Info)

Using the above mentioned formula, the steam at 2.8 bar (40 psi) and 150 degrees celsius (302 fahrenheit) would exit at 600 meters/second in normal atmosphere (15psi).
This is a Laval nozzle output speed.

That means the best blade speed for the impulse turbine is aprox. 300 meters/second (or 60000 rpm for the 4" rotor)

However, We dont really know what your actual nozzle speed was.
--------

cezar

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#20)
by Brian H on Mon Mar 12th, 2007 at 03:39:22 PM MST
(User Info)

Very interesting project! Can't wait to see how it turns out! Conventional wisdom says that steam turbines are not cost-efficient on a small scale, due to high temps/pressures and especially "dryness" (lack of water droplets) of the steam required to get high efficiencies from them. You are going against the grain, which is sometimes how great leaps are made!
During my 4 years as a mechanical operator in a US Navy nuclear reactor, I operated a few different types of high pressure steam turbines. Only one was single stage. It was very low RPM (for a steam turbine) as it was directly coupled to a fairly large centrifugal pump (no reduction gears). The design looked much like "the crown wheel off a worm gear" as ruddycrazy described. In conjunction with that shape of turbine wheel, the casing has a similar spiral groove cut in approx. 180 degrees of it's shell, such that it caused the steam to spiral round and round, striking the turbine wheel multiple times before exiting the case to be condensed.
I see a few obstacles standing in your way to making this a successful venture.
First, and foremost, removing any entrained water droplets from the steam, no matter how small. Your steam needs to be 100% water vapor(well at least 99%), with no entrained droplets. Conventional steam plants accomplish this by means of superheat. Superheating (heating above saturation temperature) ensures that no "carryover" of water droplets makes it's way into the turbine. The main reason for this is the extreme velocity that steam leaves the nozzles. Any entrained water droplets will act just like tiny bits of sand at that high velocity, and will impinge on your vanes, and quickly erode your turbine wheel, no matter what it's made of. Absent superheat, you will need a very good moisture separator between your boiler and your turbine. Some type of cyclonic, or chevron arrangement (or possibly a combination).
Second, you stated earlier that you achieved 100 watts from a smaller version, and I don't doubt you, but I'd be very interested to know what was your energy INPUT to achieve 100 watts OUTPUT? Maybe this doesn't matter, maybe you are making all this steam anyway, to heat your greenhouse, and/or other things, and you are not so concerned with efficiency of your turbine, but just need to generate some electricity "off-grid" which is fine for you. But I am very interested in efficiencies myself, as I don't have an abundance of steam at my disposal, and want to generate my electricity as efficiently as possible. And conventional wisdom says that reciprocating steam engines are much more efficient on a small scale, so that is what I have been looking at. But maybe you are onto something here, and I hope you are!
I wish you good luck in this, you are obviously a very skilled machinist, and have put a lot of time and effort into it, and it looks like you are well on your way! I hope that my modest experience with steam and steam turbines has added to the discussion, and will be looking forward to your progress!
Best Regards,
BrianH
"Remember, I'm pullin' for ya'! We're all in this together!" - Red Green
[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#21)
by blimpyway on Tue Mar 13th, 2007 at 08:43:14 AM MST
(User Info)

He states somewhere he used a 60000 btu boiler at 1/4 its capacity. That means 17/4 kw, or aprox. 4.5 kwatt to heat the steam. 100watts out electrical makes an overall 2.2% efficiency, but I think there is much room for improvement.

I would not be so picky about efficiency as long as I can put enough into batteries. Winter heating needs a lot of thermal kwh, and 5-10% might be enough to suply a good slice of the electricity needs during winter.

cezar

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#22)
by WXYZCIENCE on Tue Mar 13th, 2007 at 09:46:42 PM MST
(User Info)

cezar, September 2006 the winter started here in northern Alberta. March 13th 2007 the winter is still going strong. Co-generation in a workable form is where we are headed. Thanks for your interest. We are also working on other smaller steam projects that will teach us what not to do. Having more fun in the doing.
Joseph.

[ Parent ]

Re: Impulse Steam Turbine (3.00 / 0) (#24)
by spinningmagnets (velmis1450bc(at)aol(dot)com) on Sun Jul 15th, 2007 at 06:41:46 PM MST
(User Info)

Dear WXYZCIENCE, Great project! If you have ready access to plenty of wood (or anything else that burns!) you can get electricity when there's no sun, wind, or water flow. You're probably already going to be using what I'm about to suggest, but just in case...

Definitely use a heat exchanger from the boiler exhaust or condensing steam to pre-warm the feed water to ~200F. The less interior boiler heat that is used to warm the (I'm guessing) 60F cistern water, the more boiler heat will go into the steam vapor. This will give the steam more power and make it dryer, and the leftover water will still be ~130F, plenty warm for a radiant floor heat system.

Definitely use synthetic lube oil. I don't recall what type, but a little steam always got into it, and we used a spinning cylinder to separate the water from the oil. -Ron

"how many psychiatrists does it take to change a lightbulb"?

"only one,...but the bulb has to WANT to change"

Impulse Steam Turbine | 25 comments (25 topical, 0 editorial)

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