Stirling Turbine

[Tom Booth]

Wow...

This (or a very similar) idea has already been patented several years ago and the company (Kender) is now selling stock. Very cheap (.39 cents).

I'm now seriously considering trying my hand at playing the stock market...

http://www.otcpicks.com/kender-energy.htm

And no... I don't work for them... would I be giving away their secrets ?

oops...

P.S. I was wrong. the current price is .055 (five and 1/2 cents)

Apparently they have gotten a lot of negative publicity. People think it is a scam.

I wonder.

[dalekh]

Tom,

Wow, the link is, uh, interesting. There is a lot to learn about this idea of yours on that thread. I haven't had time to get very far on the air cycle or turbine ref. yet. After reading the other thread, I think the true challenge is regarding whether there is an actual temp. difference between the source - atmosphere, and the final sink - atmosphere? All other aspects of what you are trying to do seem at least theoretically possible. If the energy to drive the system comes from the atmosphere, and the temp. difference required to use that energy is ultimately created using this same energy, we may well be at a dead end. (Sort of like using falling water to drive a pump that creates the falling water).

On the other hand, is it possible that we can increase the power or efficiency of the Stirling using this idea? Perhaps this is a more fruitful direction - adjusting the design to allow heating the warm side to provide additional energy in? So, I still need to take some time to pursue this air cycle ref. Its ability to operate on smaller pressure differences seems to be a key.

Dale.

[Tom Booth]

Hi, I made an animation of this engine for the folks discussing this in the physics forum:

Here, starting with post #58

http://www.scienceforums.net/forum/show ... 818&page=3

This is the animation:

[url]http://prc_projects.tripod.com/stirling_air_turbine_anim.html[/url]

Some of the details are missing as far as showing the full cycle but I think it shows enough to give the general idea of how this thing is supposed to operate.

BTW, the theoretical "final heat sink" as far as the engine is concerned I guess would be the cold air emitted from the turbine. In other words, basically the same as a Stirling Engine - the cold side (bottom in this case) of the displacer chamber into which the cold air from the turbine is delivered.

From there, any heat picked up from the displacer chamber is evacuated to the atmosphere where it gets re-warmed by the sun.

The atmosphere is not the heat sink in this case, it is the heat source.

It might be desirable, if this simple engine works at all, to make it a closed system and charge it with some compressed gas like nitrogen. Then the intake and exhaust would be connected to a heat exchanger.

This would exclude at least some environmental variables, in particular humidity which is often a problem with the air cycle system as the temperature of the turbine is so cold that ice builds up inside it.

I've often seen even an air tool that isn't insulated at all form frost around the exhaust port.

[dalekh]

Tom,

I found a "turbine" of sorts - on a home carpet cleaning machine. The turbine (or fan) is driven by air pulled through it by the vacuum. This then drives a cleaning brush (for upholstery or whatever). This might be useful as a model to play with on this idea. Of course, one can get in big trouble using working household items for such projects!! Perhaps a trip to the local GoodWill or ARC is in order!

By the way, you posted a link to a lecture on air cycle cooling and now I can't find that post. Do you remember it? Thanks,

Dale.

[dalekh]

Tom,

This is a tough topic to get info on. Most of what I am finding is simple overview or theoretical with math mostly outside my "comfort zone"!

I did find this patent application which goes into some detail about air cycle.

http://www.faqs.org/patents/app/20090133431

Two valuable bits of info I gleaned before my eyes glazed over:

1) They are seeking to operate at 80 to 100K RPM!!

2) They are asserting the need for very fine tolerances between the turbine and the housing, here referred to simply as "microscopic" or "minuscule". (Of course, they are not using Tesla turbines and I am wondering the reasons for this? One assumes there are reasons.)

These types of issues will keep me out of the game if they persist. But not to give up yet...

[Tom Booth]

Tom,

I found a "turbine" of sorts - on a home carpet cleaning machine. The turbine (or fan) is driven by air pulled through it by the vacuum. This then drives a cleaning brush (for upholstery or whatever). This might be useful as a model to play with on this idea. Of course, one can get in big trouble using working household items for such projects!! Perhaps a trip to the local GoodWill or ARC is in order!

By the way, you posted a link to a lecture on air cycle cooling and now I can't find that post. Do you remember it? Thanks,

Dale.

I assume you mean this one:

Air Cycle Refrigeration Systems Lecture on You Tube

I think that probably having the thing very well insulated and having some means of making the turbine do work are more important than the type of turbine... Though having said that, I'm almost certain a vacuum cleaner turbine would probably be almost useless for this kind of application. I'm thinking a Tesla Turbine built out of a few old hard drive platters. These are well balanced and designed for high RPMs - probably with a propane torch nozzle directing the jet of compressed air between the very closely spaced platters. That's what I think I will try anyway.

Before I went that far though, the first thing I would do is put some check valves on a tin can and see if it can pump air with just a candle for a heat source. No sense making some kind of precision turbine for a tin can that doesn't pump any air to power the turbine anyway.

[Tom Booth]

Tom,

This is a tough topic to get info on. Most of what I am finding is simple overview or theoretical with math mostly outside my "comfort zone"!

I know. I think I'm giving up on trying to figure out if this can work mathematically. I found some equations on a nice NASA site that looked applicable to this.

Well, when I started reading, it went on to say that NASA uses high speed computers to arrive at approximate solutions to these equations... OK... Time for me to go back to the old tried and true method. Intuition, common sense and trial end error or something.

The most informative piece I've found so far is this PDF:

http://ethesis.nitrkl.ac.in/7/1/sghosh-sarangi.pdf

Which also explains why there is not much information available. It is mostly all proprietary for a very niche market.

I did find this patent application which goes into some detail about air cycle.

http://www.faqs.org/patents/app/20090133431

Two valuable bits of info I gleaned before my eyes glazed over:

1) They are seeking to operate at 80 to 100K RPM!!

Mmm.. yeah, turbines are turbines I guess.

I was just reading something about the Turbo-expanders used for liquefaction of Gases. Some operate up to 1,000,000 RPM.

But we are not trying to liquefy helium so...

These things come in all kinds of sizes from giant industrial turbines to dime size micro-turbines, but they all seem to operate on more or less the same principle, that is, to extract heat/energy from the gas by making the gas (air) do work against some load on the turbine.

2) They are asserting the need for very fine tolerances between the turbine and the housing, here referred to simply as "microscopic" or "minuscule". (Of course, they are not using Tesla turbines and I am wondering the reasons for this? One assumes there are reasons.)

These types of issues will keep me out of the game if they persist. But not to give up yet...

My rational for using a Tesla Turbine is 1) not just easy but actually POSSIBLE for me to build. Any other kind would be pretty much impossible. 2) should be relatively easy to balance 3) Quiet !!!!!

I've seen there are a lot of patents. Not much else. I've been ignoring the patents because, anybody can get a patent these days for any hair brained idea, it doesn't necessarily mean it will work or that the information is accurate IMO.

Personally, I don't think that there is much point in worrying about the turbine.

The sizing of the turbine would depend on how much, if any compressed air can be delivered to it - at what volume and pressure.

I'd start very cautiously with a simple displacer chamber. Make a few check valves and see if it will pump any air at all.

I say cautiously because heating up a can that has no piston to relieve the pressure could probably be dangerous. Ultimately this is pumping air into some kind of tank or tube. I don't know what kind of pressure could be built up but generally speaking, any kind of tank that is supposed to hold gas under any pressure has to be specially made, Compressor tanks, propane tanks etc.

I think the best thing for a turbine might just be a regular pneumatic air tool of some sort. At least these are made to run on compressed air and not fly apart, and I know they can produce cold air...

They sell special antifreez, just for that reason.

"pneumatic tools can experience downtime from freezing caused by the formation of ice in and around exhaust ports and valves"

Speedynails

I've seen this happen plenty of times while working in a mechanic shop in Arizona in HOT weather when using various air tools.

I don't really think it matters that much what kind of work the gas does, it just has to be made to do work and then the turbine or whatever would have to be well insulated against the heat of the environment.

Of course, though, I have no real idea what I'm talking about.

[dalekh]

Tom,

I am certain you are right about the cheap plastic turbine - still tempting to mess with because it's already there. However, it is probably so ineffecient that would be hard to get any useful info from it.

So, trying to see how much compression is possible with a displacer...with my tin can Stirling I disconnected the power piston from the flywheel after it had stopped (so temp. difference was dropping significantly) and operated the flywheel looking for friction points. The piston pulled in and out nicely but the force is small. I think there is no doubt you can produce pressure but how much? Intuitively, a displacer with closer tolerance will have less "dead air" so that a higher percentage of the air in the cylinder is changing temp. So, any simple ideas on check valves? I'm envisioning some type of reed or flapper?

Dale.

[Tom Booth]

Tom,

I am certain you are right about the cheap plastic turbine - still tempting to mess with because it's already there. However, it is probably so ineffecient that would be hard to get any useful info from it.

There are at least two different types of turbines. Reaction Turbines, where the whole turbine is in the flow - like a fan and then there are Impulse turbines - like a water wheel, where the flow is directed at the perimeter of the turbine.

Both are used for this sort of thing, but for me at least, trying to build one at home, the impulse type has a lot of advantages.

Number one, in an impulse type turbine the power comes from the nozzle directed at the turbine so the casement around the turbine doesn't have to be so close fitting. With a reaction turbine, there has to be a very tight fit or the gas will just go around the turbine. With the impulse turbine, the gas is shot out of a nozzle right into the turbine to deliver the energy so a tight fitting housing isn't necessary.

Reaction turbines usually use inline pressure flowing through a pipe or duct and the turbine has to be IN THE DUCT-WORK to intercept the flow. The Impulse turbine on the other hand is driven by the velocity of the gas as it leaves a nozzle. The nozzle converts the pressure in the line into velocity so the impulse turbine can really be any size as it doesn't have to be in the pipes.

The Tesla Turbine is basically of the impulse type. I think a reaction turbine would be really impossible to build as it generally has to have very well balanced contoured blades. You can make an impulse turbine out of old bottle caps.

So, trying to see how much compression is possible with a displacer...with my tin can Stirling I disconnected the power piston from the flywheel after it had stopped (so temp. difference was dropping significantly) and operated the flywheel looking for friction points. The piston pulled in and out nicely but the force is small. I think there is no doubt you can produce pressure but how much? Intuitively, a displacer with closer tolerance will have less "dead air" so that a higher percentage of the air in the cylinder is changing temp. So, any simple ideas on check valves? I'm envisioning some type of reed or flapper?

Dale.

It's possible to get reed or leaf valves ready made. Try a lawn mower repair shop. Those types of leaf valves were once common in almost all two-cycle internal combustion engines - like chain saws. They seem to have been phased out in favor of ports though.

I was looking at just making some simple check valves out of old bicycle ball bearings and some copper tubing.

Here is an illustration of what I had in mind.

I think this would be easier than trying to add leaf valves.

[url=http://prc_projects.tripod.com/Stirling_Compressor.html]Simple Stirling Compressor (?)[/url]

The ball bearings are kept in place by making a little cage out of some copper wire. All this would really take to make is a propane torch and some solder - tin snips, you know, just a tin can with some check valves mostly. The hardest parts to make would be the intake check valve - as it would need a little box to live in so it doesn't interfere with the displacer movement, and the seal around the displacer handle thing.

I figured on just putting a balloon over the exhaust pipe. Then maybe attach a bicycle pump hose - see if it will do any real work... like pressurizing a basketball...

[Tom Booth]

Hi dalekh,

I've been thinking that depending on how the "compressor" performs, it might be possible to use a reaction type turbine.

It would have to pump quite a volume of air though, and I'm not sure that the vacuum thing would work... if the turbine blades are designed to draw in air rather than be pushed by air. I know this is true of wind turbines. You can't use an airplane propeller for a wind turbine, it is designed to push the air, not be pushed by the air... Though who knows... I know some vacuums are reversible.

Anyway, whatever the design or the type of turbine, I thought it would be a good idea to have two "displacer chambers" or two of these pumps or compressors working in tandem. One drawing in air while the other is compressing so as to smooth out the flow.

Just cut - n - pasting one of my previous drawings together and adding a rocker arm to give an example of the general idea...

At the bottom of the page.

I also came to the conclusion that it might make more sense to pre-cool the turbine itself, rather than pre-cooling the air to the turbine. There is also a drawing of one way this might be done on the same page.

Pre-cooling the gas before it reaches the turbine is the usual way things are done in liquefaction processes but here, I'm not really looking to liquefy the gas but just expand it into a cold turbine so that it will have to use its own heat/energy rather than drawing energy from the surroundings to do the expanding. Pre-cooling the gas works for liquefaction or cryogenics where power output from the turbine is not a consideration, but here power output is important so I think pre-cooling the turbine rather than the gas would leave more energy in the gas for expansion through the turbine but it should achieve the same cooling effect as pre-cooling the gas itself.

[url]http://prc_projects.tripod.com/turbine_detail.html[/url]

[stanhbaker]

Dubbing a thermal device of some sort as being Stirling does Not make it a Stirling engine which is a unique design of a closed volume of gas (a generic term) such as air, helium, hydrogen, or one having the right thermal properties.

One portion of the Stirling engine is heated externally to as high a temperature as is compatible with the heat source and the materials of construction of the HOT end. The opposite or cold end is cooled to the lowest possible temperature by readily available cooling water, etc. but not by artificial means at that consumes more power than the Stirling engine can procuce. SOME power is extracted as mechanical power. It should be noted that the amount of heat entering the engine must equal the sum of the equivalent of the mechanical power plus the amount of heat ejected or lost to the cooling medium.

Turbines, valves, etc. are not applicable to a Stirling engine. IF you really understand what a Stirling engine is then you should have little trouble in rejecting some of the fanciful ideas suggested above. By and large they are NOT Stirling engines!

stanhbaker

[Tom Booth]

Dubbing a thermal device of some sort as being Stirling does Not make it a Stirling engine...
stanhbaker

Well, so, technically, it's not a Stirling Engine.

A Stirling Engine is known as a "valveless" heat engine and this thing has valves.

But as far as the way a displacer/regenerator works to expand and contract a volume of air in a heated (and/or cooled) chamber to extract work, this is, as far as I'm aware, Stirling's idea or invention. At least that is where I first became acquainted with it, primarily here on this forum about three years ago:

http://stirlingengineforum.com/viewtopic.php?f=1&t=77

[tompeat]

hi i have joined this forum to say that i think a stirling turbine is possible.

the mechanics of making such a thing might involve rotors on the surface of a klein bottle
but it is still possible, dispite what other people might tell you.

when i have writen the paper i will send you a copy , it'l take about a year to finish so don't hold your breath. see you in Dubrovnik.

yours tom peat

[dalekh]

So, tom peat, being a non-mathematician I googled Klein bottle.

Yea, that's interesting. Actually, they are very interesting and I just spent my entire lunch hour messing around with them and trying to understand them. Don't know what they have to do with Stirlings, but I guess that is the point of your paper, right? :) I shall be waiting with bated, (as opposed to 'held') breath. And I most certainly expect animations of similar quality and clarity to Mr. Booth's. :)



Dale.

[Tom Booth]

So, tom peat, being a non-mathematician I googled Klein bottle.

Yea, that's interesting. Actually, they are very interesting and I just spent my entire lunch hour messing around with them and trying to understand them. Don't know what they have to do with Stirlings,...

Dale.

Somehow, I think Mr. peat was joking.

Anyway, in regard to the "air pump" or compressor aspect of this thing, I've been thinking that it would be difficult to achieve very high pressure.

As air is drawn in at atmospheric pressure, then heated - some of the air being allowed to pass out of the chamber into some condenser coils or whatever, as the remaining air in the chamber is then cooled, there would be a reliance mostly upon atmospheric pressure to "push" more air into the chamber to be heated, "compressed" or pumped.

There would be a definite limit as far as the amount of "compression" that could be achieved during each cycle, I think, which would limit the pressure that could be achieved in the condenser coils without too much back pressure keeping the check valves from opening.

It might be possible, I think, to achieve higher pressure by ganging together several displacer chambers prior to the gas being released into the condenser coils.

This would be rather like a battery cell that can only achieve 2 volts but by connecting the cells in series higher voltages can be obtained. I think the same would be true of a series of displacer chambers for achieving higher pressure.