Topic: Steam turbine (Read 49437 times)

andrewh · « **Reply #50 on:** February 18, 2008, 12:46:21 pm »

Joe,
Yes, cheerful (but irreverant) bunch on this forum

The magazine I am remembering will be Model Boats of about (guess) late 70s or early 80s - I'll see if it comes when I call.
andrew

Capricorn · « **Reply #51 on:** February 19, 2008, 02:00:23 am »

Thanks again Andrew,

Any ideas on the turbine itself? I was encouraged by Johns design (Bogstandard) above, he sketched what he thought would do the job, and he has some experience with them he said. I'm afraid he was ill though and I'm not sure he'll be able to build it.

Anyway, I took his design and put it on cad, with my own guesses on some of it. I like that it has reverse built in, and I think I'm understanding more how it works. I'm not sure I'm going to be able to make it, I have a small lathe now, but not a milling machine for the rotor buckets, plus many of the sizes are just guesses. Anyway here it is:

Capricorn · « **Reply #52 on:** February 19, 2008, 03:12:50 am »

I thought I could edit the post but don't seem to be able to.

Please delete the last pdf, jbturbine.pdf and use this one:

herrmill · « **Reply #53 on:** February 19, 2008, 03:57:24 am »

Cap,

I've not been following this thread but find your plans to build a turbine along with your 1/35 DD build over at RCG impressive.

Am looking forward to watching this one. Will a Turbina build be next?

Chuck

Capricorn · « **Reply #54 on:** February 19, 2008, 01:09:45 pm »

Hi Chuck,

It's pretty much the same thing, I have gotten a lot of input on the steam turbine part of it here. I hadn't done much on the turbine or steam plant for a while, nothing more than talk, but will need to start some time. I probably should have started with the turbinia, more appropriate for the first step I suppose.

I'm getting some input on the turbine design by John, so I'll be revising it some more. Cap

Capricorn · « **Reply #55 on:** February 20, 2008, 05:25:18 am »

Upped the size to 40-50mm range. Second of many iterations.

Capricorn · « **Reply #56 on:** February 20, 2008, 05:31:35 am »

Check out this crazy idea (see pdf). To be able to make it this one is mostly a bunch of discs rings and holes. The steam goes in one side where the holes are smaller, as it flows through progressively larger holes it is thrust back and forth through the stators and rotors, much like a regular marine turbine, but using angled holes rather than blades. Again doubtful success, first the holes are straight, not curved like the blades, and being so they have to be more oblique. But if more holes were used so it's almost like all that is left are blades maybe it would work a bit. Comments?

andrewh · « **Reply #57 on:** February 21, 2008, 01:18:15 pm »

Hi, Capricorn
Declaration of interest -I'm and engineer who has worked with steam turbines since I was 17, (but none smaller than 60 MW - about the size of a small house with boiler).

Small turbines have snags that can be hard to overcome - especially leakages, sealing etc.
Look how long it has taken for gas turbines to get small and efficient. They have benefited from the work done on car turbochargers, and steam turbines should be able to as well!

Pre-forgive a short lecture.
Probably worth getting the basics in.
There are two ways to get the energy out of steam (or any other gas):
Reaction and Impulse (to be difficult some turbines use a bit of both)

Reaction basically reverse the direction of the fluid (steam) and the turbine wheel picks up the energy - the turbines with "U" shaped notches or buckets are pure reaction machines

Impulse - usually airfoil blades, and they act as rotating wings in the steam flow. All big generator steamers are of this type - lots and lots of rows of rotor blades (getting larger as the steam pressure drops) with fixed stator blades between them to reverse the flow.

Lecture over - you can come out now

Thoughts on the "johnsturbine"
- nice, neat and makeable
- good idea to have a reverse feature - since the reverse is not required for high power the "pockets" can be cut in the side of the forward wheel
-Will need a high reduction to the prop - I wonder if the turbine could drive a electrical generator and then the prop could be electrically driven?

Thoughts on the crazy idea
-good crazy idea! I have no access to machining but I do have a friend with YAG laser - hence lots of identical holes are simple
-it works by reversing the flow - it is mainly a reaction machine - the holes don't have to be curved
-worth a try!

All these turbines and ideas can be tried with commpressed air - I think you have said this previously.
Model boat steam is hot, but not very hot.
Materials like bakelite, silicone rubber are perfectly happy at these temperatures
How about moulding the "body" of the johnsturbine in a silicone potting material - possibly with side plates holding the bearings
for a trial - make 1 rotor (in aluminium?) on 1/4 inch shaft with ballraces
Hold it together as a sandwich with a ring of bolts
see how it goes!

Reduction gearing - possibly an epicyclic gearbox with large reduction - about 50:1 (guess)
I have lots of dead electric drills - this is what they wear on the front
It might not be efficient , but it might work!

To begin with - we should not be seeking elegance or efficiency - we need first to get the thing to overcome its internal friction, then to deliver a little power to the shaft, then more and better power

How goes the hull?

andrew

bogstandard · « **Reply #58 on:** February 21, 2008, 03:11:13 pm »

Hi Andrew,

The single rotor phase has already been proven.

http://www.youtube.com/v/wImhE-zNTgk&rel=1

During the first runnings the bearings were preloaded to prevent runaway past the safe bearing speed of 45k and to slow it down faster so that three runs could be got in in about 2+ minutes, without having to wait too long for the rundown.
One the second vid, the generator load keeps it from running away, but still reaches a very good stable RPM.

http://www.youtube.com/v/KW6V7JWbQwk&rel=1

The turbine shown has a 60mm diameter all brass rotor, with a 6mm thru shaft. The triple rotor one should have a 40 to 50mm diam rotors, again out of brass but with 5mm shafting.
I understand where you are coming from by using the pockets in the side of the rotor for reversing, but I designed this for actually running in reverse at fairly high speed as well, and it is rather difficult to get the jet totally concentrated and contained within a specific channel when impingeing onto the side of the rotor, hence my design for a separate reverse running rotor.
In fact the main rotor would be made in one piece, with 18 pockets (20 degree spacing) either side of the machined wall, but the pockets between the two sides would have an offset of 10 degrees between them to allow an even smoother running rotor, in effect having 36 pockets at 10. deg apart.
This engine, with a gear down of 15 to 1 should give a very good output for say a four or five inch prop. But the gearing comes later and needs to be proven after the engine is fine tuned. But I have a special inifinitely variable gearbox that will sort that out in no time, to give the best results for power output.

John

andrewh · « **Reply #59 on:** February 21, 2008, 04:24:22 pm »

John,

Forgive me, I had probably not read your posts sufficiently carefully and had not realised how far you have got

Thanks for the information and references - I will study with interest

Certainly I was not trying to teach you to suck eggs.

Since I am an engineer without machining capability I tend to imagine kitchen table solutions to devices, and this was the line I was thinking down.

Capricorn has a lovely hull, there - and the desire to turbine it!
Anything I can do to help, I will

I came across this, today
http://www.john-tom.com/ElmersEngines/12_turbine.pdf

best regards,
andrew

bogstandard · « **Reply #60 on:** February 21, 2008, 06:06:19 pm »

Andrew,

No need to apologise at all, in fact it is nice to get a bit of conflicting input sometimes, makes you think down different routes.

I studied the Elmers turbine a couple of years ago, and it is rather basic, with a lot of hand finishing required, plus the shape of the blades wasn't very helpful at getting rid of the exhaust at high speed.

John

Capricorn · « **Reply #61 on:** February 22, 2008, 12:15:45 am »

Thanks John and Andrew, all this is greatly helpful to me. You are both so experienced in turbines and steam, along with everyone else I think I'll be able to do this.

The john-tom stuff is great, I was heading that way (on paper) for a while with a disc and holes drilled in it around the outer edge, but didn't take the final step of machining off the edges of the holes to form the cups, that looks like something I might be able to build. Will keep it in stuck away on hard drive, hopefully easier to find then in loft but not for certain.

The sketch with the plates with holes that I posted here is interesting but I have some reservations about it (probably doesn't work, certainly not how shown).

I'm going to try one more experiment with the computer fans. Here's a movie of the first:
http://s262.photobucket.com/albums/ii92/capricornzzz/?action=view&current=MVI_0565.flv

This time I'm going to use the thin 60mm fans with 11 blades and see if I can make a regular turbine alternating rotors and stators, mostly just for experimental sake. The main problem (besides the blade spacing) is that when I flip them the airfoil shape of the stators will be somewhat backward, which I assume, theoretically and practically nullifys them, but I guess I've got to experience it myself until I'm satisfied.

Here's a more developed idea which is certainly farther than my experiment would likely go. Originally I got pushed to the small ones to get higher rpm and ran the steam in tangentially. But I was really impressed how much torque this 60mm fan blade had under the compressed air, I just have to find some way of utilizing the wind off the first blade on more blades.

In any case I think the one with the fingernail buckets is the likely one to go farther, so I certainly haven't abandonded it just taking frequent detours

.

Thanks again for input, and don't take any of the sketches to seriously they are always at best half finished (for instance it occured to me, like John said to offset the buckets (or nozzles) on the double forward rotors to provide more constant pressure on it)

bogstandard · « **Reply #62 on:** February 22, 2008, 01:33:24 am »

In the fan turbine you might require some fixed vanes in between to straighten out the flow before it hits the second set of blades. As the pressure is coming off the first set it would be very turbulent and going all over the place.

John

Capricorn · « **Reply #63 on:** February 22, 2008, 02:43:56 am »

Hull progress good, all but the very tip of the bow is done:

http://i262.photobucket.com/albums/ii92/capricornzzz/thIMG_0599.jpg

Plenty of room (I think), and should have 70 to 100 lbs payload (minus hull), but some of that may need to be bottom ballast.

John, I'm not sure if you are referring to the fanturbine on the movie or the drawing, I've got so many versions going it doesn't help. I assume the drawing, there I should have been more clear, the (red) fan blades would be fixed, although they look free, I didn't show the connecting piece, but it would be something like what the fans use, maybe four struts, each fixed fan blade hub would have a ball bearing so they stay centered on the shaft and probably thrust bearings between each fan. The shaft would have one flat side and the rotor fans would key onto that and then via all the thrust bearings the whole thing would be held together from the ends (didn't show that either). The taper I'd as soon skip, likely to destroy the blades for one plus make the thing a lot more work to build, it's just that they always seem to have the taper for expansion.

I've been prodigously drawing different turbines, check out the latest one, an impulse turbine again I think but with four small nozzles and two stators and two out rotors to try to pick up a bit more energy from the exhaust. Splits the jet like a pelton wheel type (or whatever they are called).
This time no color variation, but the center one and the two outer ones turn, the other two would be fixed somehow. It's just so hard for me to anticipate how sharp the curves should be etc, no idea if it would even turn.

bogstandard · « **Reply #64 on:** February 22, 2008, 11:42:52 am »

The probs with how you have it is, where do you get rid of the exhaust?
In basic format this rotor would be open to atmosphere, but in your situation, not a very good idea.

If all goes well and I recover to clear my backlog, in about a month or so I could make a prototype, but had a look at my stock this morning and the largest rotor I can make is about 35mm, 5mm of that would be the seperation wall. The cost of prototyping a larger one would be rather expensive. But the smaller one would prove the motor and give some figures for expected power output.

John

Capricorn · « **Reply #65 on:** February 22, 2008, 01:21:06 pm »

John, That would be great if you build a prototype, do you have bearings and everything? How much do you think a larger one would cost? The boat has two propellers, and although I was thinking one large turbine, it may be more effective to use two since they are smaller. (Can you make two that turn in opposite directions?

!)

What's the special infinitely variable gearbox? That sounds intriguing.

Andrew, since you work with the bladed turbines I was wondering how much the airfoil shape does for them, obviously it's important, but if the stator blades have the airfoil reversed how much affect would it have do you think?

andrewh · « **Reply #66 on:** February 22, 2008, 02:14:31 pm »

Gentlemen,

I have just posted a turbines in practice brain dump on
http://www.rcgroups.com/forums/showthread.php?t=816710&page=3

I will (mercifully) not subject you to it here.

John, I have viewed the turbines running, beautiful workmanship and sweet balance!
Capricorn, we are studying at the feet of a master!

Having seen and heard them I have become quite motivated to learn more and experiment a bit
Capricorn has started with computer fans - and is, I think, mainly using them as a quality set of bearings carrying a regular set of blade tips (this is good!)

I saw another video using my preferred basis - a Computer hard drive motor. These have quality bearings and machining, a generator in the middle (if required) and need only the addition of the blading to commence turning!

Also I have several (I rewind brushless motors for model planes and boats)

andrew

bogstandard · « **Reply #67 on:** February 22, 2008, 04:29:44 pm »

Gents,
I think you are missing a very important point here.

STEAM. It is 'orrible stuff when working with it, and introducing it to bearings and fine wiring soon shows how nasty it can be. Even fairly high quality stainless bearings that I use suffer, I reckon between 30 to 40 hours running and it would be time to change them. That is why I went for a modular system where a bearing change could be done in less than an hour. The way 'toy' turbines work is by venting to atmosphere on the opposite side to the support bearing. In large engines they have power to spare and so they can afford to lose a bit of efficiency by introducing complicated sealing galleries to protect the bearings.
In this type of engine we can't do things like that, so we have to attempt to channel the steam where we want it to go, even though we haven't extracted all the power out of it, maybe a small secondary turbine could be run off the exhaust, but that is getting ahead of ourselves.

With regards to building two, running in opposite directions, no problems. But the first stage is to see if the small prototype has the properties to give what we want.

With regards to the variable gearbox, here is a picture of it with the rotor and generator from my turbine. By twiddling the little knob on the side of it you can go from 1 to 1, to 1 to 500, on the run. I have only ever seen one at this size, and I've got it.

http://i202.photobucket.com/albums/aa102/bogstandard_photos/3turbinerotorfinished.jpg

John

Capricorn · « **Reply #68 on:** February 22, 2008, 11:40:17 pm »

That's a dandy looking turbine John. The gearbox, it must not be gears I take it, it wouldn't really be infinitely adjustable then would it? Or maybe it has some sort of diffential in it, have you peeked inside? Or is it secret?

I understand what you say about the steam being hard on the device, it must be simple to for my use too, changable bearings certainly shouldn't be a problem. In my case they wouldn't probaby have a lot of run time anyway, unless I rent a slip for it which isn't likely.

I did plan on running fairly large pipe or pipes from the exhaust back out the funnel, maybe through a condensor, just because it would be fun to build a water cooled condensor on it too, if there is room and can take the extra weight. How big of exhaust pipes do you think it would need to be low pressure enough?

I'm going to need to think about the boiler or boilers again, with the tubines relatively small, I could put in two relatively large boilers (if needed), the two compartments are roughly 7" high x 11" wide x 17" long, with some room into the above deck room, each with it's own funnel (convienient for sure). But I sort of planned on one boiler in the front room using the front funnel, and the back funnel would be for the steam exhaust, so if I used two boilers the stacks would have to be shared between steam exhaust and heat exhaust from the burners, I suppose a simple divider would keep them from spilling steam down into the burners. There is also a pipe with a downturned funnel on the end, much smaller, I'm sure you know what I'm referring too (if not see picture of fletcher, on the back of each main funnel are the little ones), I'm not sure what they were for, maybe diesel generator exhaust? I had thought they were the steam relief valve outlets which is what I was going to use them for.

Andrew, thanks for the info on turbines, I never was quite sure about the difference between impulse and reaction, so that clarifys it for me. The computer fan "turbine" that I made was basically an impulse turbine with the tangential flow onto the tips of the blades. (I actually gutted the wiring and had to use my own larger bearings but I saved all the fan bearings for later use in something).

andrewh · « **Reply #69 on:** February 25, 2008, 02:19:13 pm »

Bother - Just lost the post for the second time

Sketch of my trial turbine attached - might get it cut in the next couple of evenings

Where are are you in the New World, Capricorn?
andrew

Capricorn · « **Reply #70 on:** February 25, 2008, 11:40:59 pm »

Andrew,

That looks good, how do you cut the buckets in? Wondering what you will use for the housing too (polycarbonate it looks like). Can you seal it so steam doesn't get into the electric motor? What is the motor rpm listed for?

I live in Minnetonka Minnesota, just west of Minneapolis. It's been the dead of winter here for a month now after a warm early winter, seems like a pattern now, but finally starting to warm up. Ice out of the lakes is usually in April.

bogstandard · « **Reply #71 on:** February 26, 2008, 05:14:37 pm »

Hi Andrew,

Looks a very good design, and should work well.

Be very careful on initial trials as the bearings might be designed for high precision and smooth running, and designed for hard drive rotational speeds (somewhere between 7 - 10K). These types of turbines will, if made correctly will reach over 300K. On my inititial trials I preloaded mine to keep it about 40K max. Bearings have a bad habit of actually exploding, so as much safety precautions as possible.
I can't believe what some people get up to on utube, they take such unecessary risks.

Good luck with it.

John

andrewh · « **Reply #72 on:** February 27, 2008, 09:17:54 am »

Good Morning, (and it is)

Did the earth move for you, in Crewe, John?
Our house is a gravity structure (110 year old lime mortar) so I need to have a look for any movement

Thanks for the observations and advice - I know that steam is searching and fairly evil - in all honesty I am aiming to use this motor chassis and a sacrificial proving gadget, and if the bearings croak, they croak.

Safety will be taken seriously - my 12 year old will be assisting me and I aim to show him that "everything is possible, bounded only by safety and society"

It will be tried on air to begin with - a little kinder and more controllable

Couple of pics attached of the victim motor - sorry about the focus - my camera needs good "Verticals" to pull a good focus and clearly didnt find any. The buckets are only freehand penned at the moment.

It works very well as a motor - I have brushless controllers for my planes, and since there are 3 wires it was not too difficult to fiigure the connections - it spins well on 6V, very well on 7.2V and wonderfully well on 12V.

Cutting the buckets? I have no machine tools or dividing head so I will use the best kit I have - drill stand and dremel with either a home-made end mill or (more likely) diamond burrs - I have a cutting plan in my head but can't describe it - I will take pics as I go.

andrew

andrewh · « **Reply #73 on:** February 27, 2008, 09:25:26 am »

Capricorn - the trial setup will use an aluminium plate as the motor end plate (with a hole for the wires to emerge)

The main "block" will be a high quality plywood (safety and availability) and the open end cover will be Perspex or (most likely) polycarbonate

When I see how it goes I will either continue with electrical generation or revert to high-geared mechanical drive

Thinks - the motor running as generator will produce 3-phase AC, and I (probably) want single phase DC so I need to hatch a rectification scheme that gets to where I want.

An alternative might be to feed the raw output straight into a similar 3-phase motor!
andrew

andrew

Capricorn · « **Reply #74 on:** February 27, 2008, 01:29:01 pm »

Andrew, Where are you located? Did you have an earthquake?

That looks like a pretty nice motor, I haven't got any of those. A turbine electric drive would be a slick drive system. Been pressed for time the last couple days but am eager to hear how it goes. It's good to have the generator part of it, easy to put load on the turbine.

Joe

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