Steam turbine generator

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dusty
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Re: Steam turbine generator

Post by dusty » Tue Sep 14, 2021 7:46 pm

Steamer Al wrote:
Tue Sep 14, 2021 2:33 pm
Also interesting to note that some of the compressor blades in modern high bypass turbofan engines on airliners are investment cast. Although I'm sure its an alloy we could only dream of getting ahold of!

https://www.foundrymag.com/molds-cores/ ... ine-blades
The blades discussed in the linked article are used in the HOT section of the engine, not the compressor. And it's not so much the alloy their made of (typically close to a standard INCONEL) that makes them so strong and heat resistant, but more the internal design and manufacturing process. As the linked article describes, after the blades are cast, they're placed into a vacuum chamber where they're induction heated to near melting, then allowed to cool very slowly which allows the metal blade to form into a single crystal, which is far more heat resistant then a standard casting. Also notice the many small holes in the blade being held; modern hot section turbine blades are cooled by routing a small amount of high pressure air from the compressor into internal air channels cast inside the blades, thereby cooing the blades both internally and also externally as the cooling air blows through those many holes and forms a thin laminar air flow over the blades external surfaces. High pressure turbine blades in a typical gas turbine engine are subjected to combustion gases at 1500 C (2732 F), temperatures which fortunately steam turbines never reach.

I think it's safe to say that we hobbyists can safely use standard casting methods and standard alloys for our steam turbines. :D

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Steamer Al
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Re: Steam turbine generator

Post by Steamer Al » Tue Sep 14, 2021 9:31 pm

Wow thanks for the fascinating explination!! Not much comparison to hobby work as mentioned but interesting none the less.

rrnut-2
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Re: Steam turbine generator

Post by rrnut-2 » Wed Sep 15, 2021 11:04 am

" As the linked article describes, after the blades are cast, they're placed into a vacuum chamber where they're induction heated to near melting"

They are also cast in a vacuum, both the turbo wheels and the jet engine parts. They are also heat treated in vacuum heat treating ovens and are not induction heated at this foundry. The alloys that are used, we could not afford to use in the hobby.

Jim Bronson

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Dick_Morris
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Re: Steam turbine generator

Post by Dick_Morris » Sun Sep 19, 2021 5:41 am

I'm making some progress. I did some test prints to check for fit and appearance. There are still lumps and bumps to add as well as finishing the turbine cover and turbine end bearing cover. After I get the parts to fit and look right I will print them in castable resin and cast them in silicon bronze.

These little motors are sure tiny!

These are both out runner motors, meaning the stationary coils are on the inside and the outer case contains the magnets and spins with the shaft. Out runners are larger diameter and shorter and will fit into the case where the the in runners of approximately the same power would be too long.

I bought two variations. The larger one has the output shaft and mounting flange on the same end. The smaller has them on opposite ends. They both fit, although I'll need to put in a trough to hold the wires on the bigger one to prevent interference. On the other one the wires are on the back side.

I made up a bridge rectifier to convert the three phase AC output into pulsating DC. a good sign was that when just spinning the shaft quickly with my fingers and only the volt meter for a load I was able to momentarily get half a volt. Next I'll do some testing to see how much they will put out by driving them in my mill, which has a VFD so it can be set for a specific, repeatable speed, and I will use an infrared tach to set the rpm accurately. I will drive a resistive load and use a multimeter to check current and voltage.
Attachments
in hand.jpg
in-hand 2.jpg
3.jpg
Last edited by Dick_Morris on Sun Sep 19, 2021 6:26 am, edited 2 times in total.

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Dick_Morris
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Re: Steam turbine generator

Post by Dick_Morris » Sun Sep 19, 2021 6:19 am

I remembered I had a number of reprinted International Textbook Company/International Correspondence School lessons in my collection of tech data and found the lesson on "Headlights." About half of the content is on turbine generators and there is a good explanation of the Pyle-National K-240.

Before I found this I was puzzling over how the steam was used in the K-240 as it has two wheels with a space between them. Now it makes sense. The third file helps to explain how it works but it appears that instead of reversing buckets covering the entire periphery of the wheels that there is only a short section of about six or eight reversing buckets.
Attachments
k240-1.jpg
k240-2.jpg
K240-3.jpg

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