steam turbine and generator

[Joseph NociParticipant @josephnoci48468]

Use one of the 3 phase brushless motors either from the RC helicopter or RC car racerworld. They are the ‘in-runner’ type, and esp the helicopter motors, will do up to 50 to 60000 RPM. The smaller T-Rex ‘copter motors run from typically a 22 volt battery pack, and at 60000 rpm, ie, about 3000 RPM/volt. They are VERY efficient, and just as efficient as generators ( or rather, alternators) at 60000 RPM you will easily get 50volts at8 to 10amps from such a motor ( about 35mm diameter and 65mm long). Use 6 diodes to rectify and away you go. Although, I suspect that 500 watts is somewhat an overkill; in a steam turbine to deliver that power will be interesting…

There are lots of smaller motors in that type, down to around 80 to 100 watts as well.

The ‘out-runner’ type, where the outer case containing the magnets rotates, is not good for high speed, but great for high torque. In the ‘in’runner’, the inner rotor ( again, the magnets) rotates, and the outer plus windings is stationary.

Build the turbine first and see what is can deliver.

Ciao

Joe

[macmarchParticipant @macmarch]

As far as the bearings are concerned, perhaps someone here is familiar with the turbines used in model jets. I forget the manufactures name but the shaft spins in excess of 300,000 rpm.

ray

[macmarchParticipant @macmarch]

Just remembered, Shrecklin developed them. Like steam turbines they gulp fuel as fast as it can be poured in.

ray

[Ian S CParticipant @iansc]

Hi Paul, the idea was toung in cheek, but you must admit in would be a great bit of watch making. You could always go the other way, put a battery in the tender, and an electric motor in the casing. Personally I’d stick to a simple two pole rotating magnet alternator.

ray, I seem to have heard that they use ceramic bearings. Ian S C

[Paul HorthParticipant @paulhorth66944]

OK Ian, sorry for being dumb! Not for the first time…

The thing is, some people are ambitious and talented enough to make what you suggested. Not me though.

Paul

[Richard ParsonsParticipant @richardparsons61721]

What Mr Paul Horth really wants is to make a small simple machine which uses the waste and surplus steam to generate enough electrical power to provide light.He is talking that he needs of some 1 to 5 watts.Since the machinery he wishes to use is very small, in fact they are so small that they have dropped off the ‘bottom of the tables’.What do I mean?Most ‘engineering and physical algorithms used to make calculations contain ‘approximations’.These are usually derived by ignoring terms whose value is very small.I found that the efficiencies of a small turbines is very very small, so the requirement for an output of 1 to 5 watts could require an input of some 100 to 1000 times the required output value.Think about the ILMEC efficiencies where the winners’ efficiencies are of the order of 1 to 2%

A workable small steam turbine generating a few milliwatts and powering small tungsten filament lights is fairly easy to build.Such a machine would be a rotor of the Stumpf type (with buckets end milled in to its periphery) or the DeLaval type used by Mr Jeggi which incorporates the magnets and bearings running on a stationary shaft

The rotors Mr Horth wants to use are larger than those I used in my experiments. His is a 1.5” diam rotor and mine were from 0.75” to 1.25” diam.It is quite fun using a monotube boiler heated by two large butane burners and fed by a largish motor driven gear pump and a twin cylinder piston hand pump.In our conversations and letters Professor Chaddock’s work was leading towards the development of very small gas turbines.The modern approach is used by the successful gas turbines is different.

I understand well Mr Bakers trials and tribulations.The blue and seized ball races, the nasty scream as gears failed, the destruction of the cases as a rotor disintegrates.

So long as Mr Horth keeps the output requirements small (milliwatts) it can be done without the need for to high speeds, huge volumes of steam.The best thing is to make a rotor and casings and ‘suck it and see’.If the steam pressures are low you should be OK.

Good Luck

[Paul HorthParticipant @paulhorth66944]

Richard,

I agree with most of what you say. I would just note that Herr Jeggli has produced 4.5 watts from a rotor 30 mm in diameter running at 40000 rpm, and a boiler which fits inside a Gauge 1 loco and runs at 4 bar. So, it is possible to produce some watts without a huge amount of steam.

I would like, as you say, to make a small simple machine, but would hope to improve on the bucket-type impeller and thereby get a little more power, though I am sure that I cannot compete with the Jeggli turbine. For this I would expect to need a generator which would run in the range 20000 – 40000 rpm. I would not try to use a divergent DeLaval nozzle to get supersonic steam speed because I don’t expect this velocity can be efficiently used in the simple wheel.

Paul

[Keith LongParticipant @keithlong89920]

Not sure if it’s been mentioned earlier but have a look at Tubal Cain’s “Building Simple Steam Engines No 2”. There’s a simple turbine device with the wheel “pressed” out of copper sheet. It might just give some food for thought.

Keith

[Richard ParsonsParticipant @richardparsons61721]

The ‘Jeggli’ type DeLeval is not so difficult to make.Each blade is curved.The inner curve (on the inner edge of the blade) has a larger radius than the outer radius.I used to make two cutters by drilling a suitable bit of silver steel and then mill or file saw like teeth on the end to make a tiny hole saw.You set the thing up as shown in the attached crude drawing.As you will see most of the saw clears the metal blank

The ‘outside hols saw’ is made similarly but has a smaller radius than the Inside saw. It cuts the outside radius of the blade.It will have to be made and set up by eye.However in the small sizes 20-40mm diameter the outside of the blade is not so important.

[TerrydParticipant @terryd72465]

Hi Richard,

 

I could engrave on the head of a small pin in 12pt font what I know about turbines. Could I just ask a question out of interest? Is the Stumpf type impeller you mention similar to the Pelton wheel used in water turbines? I hope I have the terms correct.

 

Regards

 

 

Terry

 

Edited By Terryd on 22/01/2011 16:19:02

[Werner JeggliParticipant @wernerjeggli14222]

Posted by Paul Horth on 21/01/2011 13:27:24:

Richard,

I agree with most of what you say. I would just note that Herr Jeggli has produced 4.5 watts from a rotor 30 mm in diameter running at 40000 rpm, and a boiler which fits inside a Gauge 1 loco and runs at 4 bar. So, it is possible to produce some watts without a huge amount of steam.

I would like, as you say, to make a small simple machine, but would hope to improve on the bucket-type impeller and thereby get a little more power, though I am sure that I cannot compete with the Jeggli turbine. For this I would expect to need a generator which would run in the range 20000 – 40000 rpm. I would not try to use a divergent DeLaval nozzle to get supersonic steam speed because I don’t expect this velocity can be efficiently used in the simple wheel.

Paul

Edited By Werner Jeggli on 22/01/2011 19:46:28

Edited By Werner Jeggli on 22/01/2011 19:47:46

[VersabossParticipant @versaboss]

Today the Feb. 2011 issue of EIM (dare to mention it here?) was in my letterbox. It contains the first of a picture story  (no plans) of a Mr. Sheldrake, who built a (seemingly very successful, although the details are not out yet) flash steam hydroplane wit a turbine. 

Pictures show  the turbine wheel  (kind of asymmetric Stumpf type), the housing and the gearing (5:1). A very interesting article, I eagerly await the sequels.

It seems that the record was 32 mph; possibly it is bettered now…

Greeting, Hansrudolf

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Has anyone attempted the calculations for one of these small turbines ?

[Richard ParsonsParticipant @richardparsons61721]

TerryD Sorry for the delay in responding to your query. The buckets on a Stumpf turbine are ‘U’ shaped. The steam (or air) is directed down one side of the U and goes round the bottom of the ‘U’ and out the other side. A Pelton wheel which is specifically designed to work with water which has a large ‘Head’ but smallish volume. Its buckets are a ‘W’ shaped. It is a sort of double Stumpf.

There is one point about the Stumpf wheel. It was used on most air driven Gyroscopic aircraft instruments. The instrument’s case was ‘airtight’ and was evacuated by a venturi mounted outside in the airstream. Air was allowed into the casing through one or generally two nozzles. This simple arrangement gave them enough speed to do their business, but no power was drawn from them. From memory they were generally over 2 ½” in diameter and often over ¾” wide. The buckets were milled quite deep (well over 1/8” deep) and relatively few in number.

Michael Yes, but I had a large IBM that I could use and wrote in Fortran4

[TerrydParticipant @terryd72465]

Hi Richard,

 

Thanks for that explanation, I think that I now understand the processes involved.

 

Best regards

 

Terry

[Ian S CParticipant @iansc]

I,v found two refrences to Turb-generators in ME, 1986 Vol 156 no., 3769. By Terry Timms. 2008 Vol 201, nos 4332, and4334 by Ramond Mcmahon, don’t remember if either of these have been mentioned. Ian S C

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Richard ,

 

The calculations for a laval turbine or anything similar are quite straightforward and can be done by hand . This forum is not the place for long explanations but could you please outline what you actually calculated with your program ? You may have just used the computer to do these simple calculations many times over with different input parameters so as to find an optimum but if you did anything else I would be very interested .

 

I have happy memories of Fortran and spent many hours writing finite element and other programs to run in impossibly small amounts of core – first computer I ever had use of had just 64 KB .

 

Thanks .

[Ian S CParticipant @iansc]

This is the inside of an aircraft gyro, it has 24 buckets 1/2″ across, and 1/16″ deep. There are 2 inlets, 180 deg apart. Great what you find in the junk box. Ian S C

[KWILParticipant @kwil]

64KB, heaven, we had a 8KB drum store!!

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