Steam turbine generator

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jscarmozza
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Re: Steam turbine generator

Post by jscarmozza »

Thanks Bob, I'm going to try that. Correction on my previous posting, the wheels are 7/32" thick, not 7/16" thick. John
jscarmozza
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Re: Steam turbine generator

Post by jscarmozza »

I was very anxious to test the two wheels side by side, so I went to the local hobby shop and bought a little DC motor, made up a halfa--ed load center and proceeded to test the wheels. The load center didn't work, I had continuity on all of the bulbs but only one, sometimes two, would light then burn out. So I settled on just reading the DC voltage each wheel would generate. At 90 psi air pressure, Kimball's wheel generated 47 volts, at the same pressure the best the other wheel could generate was 35 volts. The testing concluded when Kimball's wheel came off of the motor shaft and ricocheted all over the shop, a quick press fit nylon adapter bushing doesn't cut it at those RPMs. I don't know if the performance would be different with steam, but Kimball's wheel seemed to be the better performer, it was also easier to make. I'm thinking that I'll use Kimball's wheel form when I make my generator. John
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Bob D.
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Re: Steam turbine generator

Post by Bob D. »

With just the voltmeter connected to the motor you essentially have a tach. There is miniumal torque load being applied. Basically your overcoming your losses.
So Kimball's design is giving more rpms and 47 volts vs less rpms and 35 volts. Volts will be pretty linear vs rpm.
Do you know the motor specs? Volts and amps? What were the bulbs? Need to know the volt, wattage or current specs.
If they are 6 volt you need at least 8 of them in series to divide up 48v.
You might not have enough motor to load up the turbine. If its a 12v motor it was spinning pretty fast!
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3/4" Hall Class 10 wheeler
3/4" Evans Caribou/Buffalo 2-8-0
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jscarmozza
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Re: Steam turbine generator

Post by jscarmozza »

Hi Bob, the only thing I know about the test apparatus is the bulbs were NPR12 flash light bulbs, which I think are 6 volt bulbs. The motor had no information, the salesman told me it was 12 volt, 10,000 rpm. I have no idea how fast I had it spinning, but I think it was pretty fast! John
John Hasler
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Re: Steam turbine generator

Post by John Hasler »

Bob D. writes:

> With just the voltmeter connected to the motor you essentially have a tach.
> There is miniumal torque load being applied. Basically your overcoming your losses.

If that's a typical hobby motor the frictional losses in the bearings and brushes are substantial. Without torque-speed curves for the two turbines you can't do more than guess, though.
Bob D.
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Joined: Thu Jun 21, 2012 10:43 pm
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Re: Steam turbine generator

Post by Bob D. »

The specs for PR12 bulb are 0.5 Amp, 5.95 Volt, 2.98 Watts,
Since you saw 47v you need 8 of these in series. Don't think you can get enough current to make them light though. Maybe try a couple of 28v indicator lamps.
3/4" Juliet II 0-4-0
3/4" Purinton Mogul "Pogo"
3/4" Hall Class 10 wheeler
3/4" Evans Caribou/Buffalo 2-8-0
3/4" Sweet Violet 0-4-0
3/4" Hunslet 4-6-0
3/4" Kozo A3. Delayed construction project

1 1/2" A5 Camelback 0-4-0
Wolfgang
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Re: Steam turbine generator

Post by Wolfgang »

I take it that the ultimate intent is to run the turbine off a steam boiler, whether a locomotive boiler where the turbine is merely an appliance as in my case, or a stand-alone plant with dedicated boiler.

That being the case the amount of steam available is quite restricted unless you have a largish model boiler.

While I have not carried out definitive measurements, I do have a qualitative idea on the steam consumption of those sceaming demons.

Before the first run at the track in the spring I steam my locomotive on a roller track in my yard, firing it with a 1 inch dia. propane torch. With the safeties blowing off I run the turbine at full power to supply the 3 LED at about 3 watts. After the safeties close it takes the full heating capacity of the torch (at 50 psig propane pressure) to maintain the steam pressure with only the turbine running!

Compare this with running at the track, perhaps hauling a few adult passengers. Under these conditions it is hardly noticeable whether the turbine is running or not. Indeed this was quite a surprise to me. Under these running conditions the locomotive might burn a model sized shovel of coal (large soup spoon heaped) every 3 minutes or so.

The moral of this tale is to encourage you to make up an air nozzle, and I suggest no more than 1/32 inch in diameter at the throat, and conduct a series of measurements whereby you note the air pressure, nozzle throat dia., voltage supplied to a load (light bulbs are ok), and the current supplied in amperes.

You will need these quantities to decide whether any changes you made improved the machine or not. Or, to decide whether one turbine wheel is better than the next, etc.

Now then, for a resistive load the power supplied in Watts = Volts x Amps. You can vary the load by adding or subtracting bulbs as needed. Use an automotive tail light bulb or brake light until you know the power you are dealing with. (Note that 746 watts = 1 horse power).

In my case I check the RPM as well with an oscilloscope connected across the generator output as this is really an alternator producing AC, and the oscilloscope measures the frequency of the output voltage. In my case this was about 10 000 Hertz (cycles per second) equating to a speed of 60 000 RPM.

Happy experimenting. w
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Dick_Morris
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Re: Steam turbine generator

Post by Dick_Morris »

I suspect that testing a turbine in the open air rather than in a housing wouldn't prove much. I also suspect that varying the form of the housing could make big differences in the output.

Don't I remember that incandescent bulbs change (increase?) their resistance substantially as they get hot?

What sized shafts and bearings do the Moseley generators use?

I've spent a couple of hours searching for my copy of the drawing for the Ulrich generator and still haven't found it.
John Hasler
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Re: Steam turbine generator

Post by John Hasler »

Dick_Morris writes:
> Don't I remember that incandescent bulbs change (increase?) their resistance substantially as they get hot?

Increase.

An AC motor such as a disk-drive spindle motor (one without the electronics built into the motor) would make a better dyno, but that would get you involved with polyphase AC, If you are going to use a DC motor try to find a ball-bearing one such as an Escap. I could send you one if you want.
Wolfgang
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Re: Steam turbine generator

Post by Wolfgang »

OOOPS, my post above should have read 1 000 Hertz = 60 000 RPM. Sorry.

As long as the set-up is the same for each test the housing will not invalidate the results of that test. w
Kimball McGinley
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Re: Steam turbine generator

Post by Kimball McGinley »

Hello Wolfgang; I like your Oscilloscope method and have done this myself, but each pole of the motor will create a pulse, so the detected frequency has to be divided by 3 or 5 or however many poles in your particular motor.
Wolfgang
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Re: Steam turbine generator

Post by Wolfgang »

Kimball McGinley wrote:Hello Wolfgang; I like your Oscilloscope method and have done this myself, but each pole of the motor will create a pulse, so the detected frequency has to be divided by 3 or 5 or however many poles in your particular motor.
Hi Kimball,

The wave form is definitely AC but certainly non-sinusoidal. More square-wavish with sloped rise and fall lines and a squiggly top and bottom. All very well defined. I'm not an electrical guy and could not design the stator and rotor to provide a pure sine wave...

However, the rotor is definitely 2-pole, and the stator has 4 coils in series; 2 coils diametrically, one wound on top of the other. Thus I conclude that the output is single phase and the measured frequency a function of the RPM. Looking at the field lamination pictured earlier may clarify things. w
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