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Author Topic: Stirling Engine  (Read 27462 times)

mindsweeper

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Stirling Engine
« on: August 09, 2007, 03:34:41 PM »
Hi all, 

I have been buzzing about the forum / TPU threads for ages now. Sort of started off down the renewable branch just lately and it's quite interesting.

So much so I just got my hands on a stirling engine and it's quite an amazing little thing. I can get it running nice and slow on 3C differential between 26C and 29C, it makes about 40RPM.

Just wondering what figures other stirling engine owners are getting with their engines.

Sweep,

joegatt

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Video clip of my stirling engine
« Reply #1 on: March 23, 2008, 11:39:32 AM »
I haven't actually measured the RPM on the one I built myself, but you can see it running here at:

http://www.youtube.com/v/i81RPxuTNO8

..and you can see it starting at
http://www.youtube.com/v/eUbMZZ_KtyA

If I can manage to build a rotary stirling engine I bet it will run a lot faster.

Regards
Joseph
« Last Edit: March 23, 2008, 01:41:07 PM by joegatt »

resonanceman

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Re: Video clip of my stirling engine
« Reply #2 on: July 01, 2008, 07:17:44 PM »
I haven't actually measured the RPM on the one I built myself, but you can see it running here at:

http://www.youtube.com/v/i81RPxuTNO8

..and you can see it starting at
http://www.youtube.com/v/eUbMZZ_KtyA

If I can manage to build a rotary stirling engine I bet it will run a lot faster.

Regards
Joseph


Joseph    are you  still here?

I was looking at  the picture of your  sterling.
Do  you still have it ?


I have an idea


gary 

joegatt

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Re: Stirling Engine
« Reply #3 on: July 02, 2008, 03:14:23 AM »
Hi Gary.

I had an idea myself, regarding this engine. It occurred to me that the displacer shaft lacked lubrication, and when that was taken care of, it went considerably faster. Pity we didn't film that. It is dismantled now, the meccano bits having been handed back to the kids.

This design makes a good demonstrator, but I am not really fond of it. I would like to build an engine with more pistons and less linkages, like an FCDA alpha stirling, with a swash plate, or with a wobble yoke.  I am currently working on a design with a rotary displacer. I thought it would be easier to build than one with multiple pistons. But in the end, the ease of construction of the humble linear piston may prove me wrong. I mean, look at what the people from cyclonepower.com have come up with!  And, irrespective of what happens on the industrial front, for the home constructor, ease of fabrication is always an issue.

Anyway, if you have some new idea, I would still like to hear about it.

Regards
Joseph.

« Last Edit: July 02, 2008, 03:51:57 AM by joegatt »

resonanceman

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Re: Stirling Engine
« Reply #4 on: July 02, 2008, 05:29:34 AM »
Hi Gary.

I had an idea myself, regarding this engine. It occurred to me that the displacer shaft lacked lubrication, and when that was taken care of, it went considerably faster. Pity we didn't film that. It is dismantled now, the meccano bits having been handed back to the kids.

This design makes a good demonstrator, but I am not really fond of it. I would like to build an engine with more pistons and less linkages, like an FCDA alpha stirling, with a swash plate, or with a wobble yoke.  I am currently working on a design with a rotary displacer. I thought it would be easier to build than one with multiple pistons. But in the end, the ease of construction of the humble linear piston may prove me wrong. I mean, look at what the people from cyclonepower.com have come up with!  And, irrespective of what happens on the industrial front, for the home constructor, ease of fabrication is always an issue.

Anyway, if you have some new idea, I would still like to hear about it.

Regards
Joseph.



Joseph

I  was hoping that you still thad the sterling in the picture .

I have been  doing  alot of thnking about water as fuel  in the HHO   section.
one thing that   is growing  clear is   an electric  arc  in water  releses LOTS of energy.

One of the main  problems    with  sterlings is  they are  external  combustion      getting  the   heat in and out is  always a big problem .
Now  it looks like  a couple of  electrodes  and  some  very basic electronics  and you can set up  an arc inside  of a sterling engine and  possably  create alot of  power  .
Sterlings  can  be over 90% efficient .........I  think   electric  arcs in  water are  over  unity ....so there is some   very  real possibilities there .

I  thought from the  picture that  your  sterling would  be perfect  to test  this  idea



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As far as a rotary  sterling .
Think  of a  ring  of  pistons  in a  circle ......  with  the  crankshaft  in the center .
If  you  have  2  rings  of  pistons like that  ............connected side by side ........so  they share  one  crankshaft ...

Then all  you need is the  duct work to connect them.
pick a piston and  go 90 degrees   one way or the other ......that is  the  other  half of that  pair
You can  have as many pairs  of pistons  as you care to make ..........just  make sure that  there is always  90 degrees in between .

As long as you have one cylinder  flollowing  another  by 90 degrees you have a  sterling .

 

one   ring   of  pistons  will  be  hot ........one cold

I think  I would make  the cylinders  stationary ........like a radial airplane  engine .



gary

joegatt

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Re: Stirling Engine
« Reply #5 on: July 04, 2008, 08:48:38 PM »
Hi Gary.

I'd hate to dampen your enthusiasm, but I myself am very sceptical about over-unity in electrolysis. Ordinary electrolysis is only about 2% efficient. Industrial electrolyzers may well go up to 80% efficiency but that is hard to obtain. And even harder still is getting the conditions right to enjoy a short bout of "cold fusion". However you are right in observing that there is heat in electrolysis that is usually lost.  Combining a stirling with an electrolyzer may be a good way to recover some lost energy ... but not much. As far as I know, Stirling engines are only 30% efficient.

The rotary you describe looks a lot like the Cylonepower machine.  On the other hand what I am working on is a rotary DISPLACER, and looks very different. Now I don't know the mechanics of the Cyclone, but it looks like it has double acting cylinders with their hot end on the inside and their cold end on the outside. I don't know anything about their fluid cycle and I suspect this device is not strictly speaking a stirling machine.


Regards
Joseph

resonanceman

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Re: Stirling Engine
« Reply #6 on: July 05, 2008, 01:18:51 AM »
Hi Gary.

I'd hate to dampen your enthusiasm, but I myself am very sceptical about over-unity in electrolysis. Ordinary electrolysis is only about 2% efficient. Industrial electrolyzers may well go up to 80% efficiency but that is hard to obtain. And even harder still is getting the conditions right to enjoy a short bout of "cold fusion". However you are right in observing that there is heat in electrolysis that is usually lost.  Combining a stirling with an electrolyzer may be a good way to recover some lost energy ... but not much. As far as I know, Stirling engines are only 30% efficient.

The rotary you describe looks a lot like the Cylonepower machine.  On the other hand what I am working on is a rotary DISPLACER, and looks very different. Now I don't know the mechanics of the Cyclone, but it looks like it has double acting cylinders with their hot end on the inside and their cold end on the outside. I don't know anything about their fluid cycle and I suspect this device is not strictly speaking a stirling machine.


Regards
Joseph

Joseph

I am  not  even a little interested in   electrolysis
If the  system  makes some  HHO  that is ok with me  .,........it will  revert back to water  when it is cooled enough .

This  forum       
http://www.overunity.com/index.php/board,104.0.html

Is all about  replicating  a    car  that  runs on water .
We are still at step 1   ......but it is  looking promising 

A few people  have  got  small engines to turn  over  using   only  water  as fuel   and  a  spark  for heat .

Anyway ......... the   spark  looks like an idea way to  get heat into  a sterling engine .



Sterlings  can  be as high  as 90 %  efficent .......but that takes  some doing .   



I have never   heard of this  cyclonepower    engine      .
I would not  use double acting  cylinders . .....   no way to  get  lubrication in  between ..........also  it is very poor thermally   if   you  have hot and  cold  that close together .


The   engine  I described   was  just  off the top of my head ....... 
I  used  to spend  alot of my free time    trying to   design  engines
Learning  how to make a rotary  sterling took me about a year .


gary




joegatt

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Re: Stirling Engine
« Reply #7 on: July 09, 2008, 08:16:43 PM »
So Gary,  it turns out that you too were interested in rotary displacer stirlings! Looks like we're both thinking on similar lines. Did you keep any photos that you can share with this forum? I still haven't figured out all the details on mine.

Regards
Joseph

resonanceman

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Re: Stirling Engine
« Reply #8 on: July 09, 2008, 09:16:31 PM »
So Gary,  it turns out that you too were interested in rotary displacer stirlings! Looks like we're both thinking on similar lines. Did you keep any photos that you can share with this forum? I still haven't figured out all the details on mine.

Regards
Joseph


Joseph


Sorry    don't  have any pictures .

I  havn't thought  much about sterlings  for  quite a few years ..........but years  ago  they were almost all that I thought  about .

Designing a   rotary sterling was a  major goal  ........it  was  very  hard and took  a long time .
Looking back   it should of  been  easy .
I was looking at one part at a time
 With sterlings   it is  the whole system that matters .

That is  why I said that  any time you have one piston following another by 90  degrees  you  have a sterling .
The  system    has less volume  when most of the  air is in the hot cylinder 
It has more  volume  when most of the air is in the  cool  cylinder
That is all that  it takes .

About efficiency   ........ have you noticed that the most efficient  sterlings   have  heat  collectors  in the  ducts between the cylinders ?    Aluminum  tubes  are  often  used for this .

As the  hot  air leaves the hot cylinder  it   contacts  the   heat collector
It looses heat  as it   passes through  the  heat collector . ......  the result is   cooler  cool cylinder

The  air  picks  up  the  heat again on its way back to the hot cylinder .
 
The   heat collector  must  be  large enough to have a   temperature gradient  along its length . 






One reason  I  lost interest  in the  sterling was because I found  a  different engine on the net .

It was called An  Entropy  engine ........
It was simple   it had a  piston in a cylinder
on  top of that was a cylinder  about  twice the size .
In this larger  cylinder  was a  paddle that  rotated .

It  was  the speed of the  rotation  that  caused   the engine to run
The  paddle  was connected to a  a pinion  gear 
The pinion  ran of a  rack  gear  connected to  a cam follower .

The  can  was designed to  for maximum   speed difference   for the paddle .

The   concept  seemed to be that it took less energy to  use rotation  to  compress   the air in the cylinders    than  it takes to compress it with  a piston
So  when the  paddle  was spun  fast ......the piston  was pulled up .
When the   paddle was moving  relatively slow  the air  rushed back to the center and pushed the  piston  back down .


The  website is  long gone .....but   when it was up they had   quite a few   reports  about  what  big companys said about it
I remember  GM    said that they  couldn't use it .    The  admitted it  worked  .......but  said it would take a motor the size of   a bus to power a car .
The  fact that they  admitted  that it  worked   was a revelation to  me
It put me  on  the OU  track

One of the main   things that people said  about the motor  was   " there is  to much  parasitic drag "

At the time I had   been into   designing  engines  as a hobby for  around 15 years .
I tried to  email them  to let  them know how to  reduce the  parasitic drag .........NO reply .


I never    built  a  test model ..........   not enough money . 


gary

resonanceman

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Re: Stirling Engine
« Reply #9 on: July 09, 2008, 09:45:55 PM »
Going  back to  what I said about the sterling

It is the  whole system that  matters .

Same thing  with this  engine

The  inventor   of  the Entropy engine  said that the   paddle worked  similar  to  a rotary  air compressor ............but  a  rotary air compressor  will not work . 

He was both right and wrong .

A rotary air compressor  will not work in  its normal mode .

It  WILL  work in  a closed loop  in a pulse mode .

My  plan  was to  drive  a compressor  disk   with a gears  off the   crankshaft
The   disk would run about  10 times as fast as  the  crankshaft .


Unlike the  sterling  this  engine  requires valves
It is the  valves that  make this  work

The  valves   decide  if the  engine is  in  compression mode or expansion mode .

In  compression mode  the  valve     going  TO   the    compressor disk is open .
The  air  in the cylinder will be sucked    to the disk .,
If   all the  air  that the disk  can pull   has already  been  pulled  the dislk will   maintain  that  condition
It  will take  SOME energy to maintain .....but not as much  as if it was  compressing more air .

In the expansion mode the valve between  the output of the    compressor  and the   cylinder is open . 
There  has  to be enough  space  behind  the   commpressor  to hold  most of the air in the system . .........this  space is  equivelent   to the hot  end of a sterling .
Heating this  area more should   provide  extra power .

Once the  expansion  valve is open  the air rushes  back into the cylinder  and pushes  the  piston back down .



Pressurizing  the  whole system  should make it  stronger . 


I thiink of this engine  as  a  turbo  sterling


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you  are like me ,  for the next few hours  you are going to have  smoke  coming out of your ears from thinking to much .


  :)


gary

resonanceman

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Re: Stirling Engine
« Reply #10 on: July 10, 2008, 04:03:21 AM »
I  forgot a little  detail  about the   compressor  disk 

It turns out that   on a disk  like this   at the  place where the  air  exits   you have a choice to make .

The normal way  to  do it is to have the  compressed air just flow  straight  out .

If  you   design  the  vanes on the  disk  so that they curve  you can  have the  air exit almost   parallel  to  the  direction of  motion .......... in other words  you can get some free thrust   from  the  air .


gary

joegatt

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Re: Stirling Engine
« Reply #11 on: July 12, 2008, 09:02:45 AM »
Yes Gary, the heat reservoir between the hot side and the cold side is important for the efficiency of a stirling. It's called a re-generator. In the case of a gamma stirling, like the one in my picture, this function is partly fullfilled by the temperature gradient along the walls of the displacer cylinder, and those of the displacer itself.

By the way, if you want to recover web pages from a discontinued website, you may find them on www.webarchive.org , if you're lucky.  But I wouldn't worry too much about it. From what you said about that O.U. design, it all sounds pretty complicated. The simplest designs are usually the best.

For example, I once toyed with the idea of using a linear motor to drive the displacer thereby eliminating leaky seals. However it turns out that, for a small machine at least, the whole setup becomes very inefficient!

Anyway, I'll try to stay focused on my rotary for now, and I promise to post pics and movies if I manage to get it running.

Regards
Joseph


 



resonanceman

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Re: Stirling Engine
« Reply #12 on: July 12, 2008, 01:57:55 PM »
Yes Gary, the heat reservoir between the hot side and the cold side is important for the efficiency of a stirling. It's called a re-generator. In the case of a gamma stirling, like the one in my picture, this function is partly fullfilled by the temperature gradient along the walls of the displacer cylinder, and those of the displacer itself.

By the way, if you want to recover web pages from a discontinued website, you may find them on www.webarchive.org , if you're lucky.  But I wouldn't worry too much about it. From what you said about that O.U. design, it all sounds pretty complicated. The simplest designs are usually the best.

For example, I once toyed with the idea of using a linear motor to drive the displacer thereby eliminating leaky seals. However it turns out that, for a small machine at least, the whole setup becomes very inefficient!

Anyway, I'll try to stay focused on my rotary for now, and I promise to post pics and movies if I manage to get it running.

Regards
Joseph


 

Joseph

The  compressor disk  would  take some doing    .......The rest of the motor is pretty simple .

I am looking forward  to  seeing  your progress.




gary


TinselKoala

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Re: Stirling Engine
« Reply #13 on: July 12, 2008, 05:58:50 PM »
I've built a few Stirlings, and I have a rotary-displacer LTD unit under construction right now. The seals are the big problem for me.
Here is a video of a small  coffee-cup Stirling that I built a couple of years ago. The power cylinder is graphite, the power piston is aluminum, the displacer is pink construction foam, the working gas is helium in the video, but air is fine too, just less efficient. It will do 600 RPM on a good day, and usually runs for 60-65 minutes on the heat from a cup of hot coffee.
http://www.mediafire.com/?2bmktk95xcx
I'll try to post some pictures of the rotary construction project. I'd like to see other's designs for this too.
Thanks--
Tinsel

resonanceman

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Re: Stirling Engine
« Reply #14 on: July 12, 2008, 09:36:46 PM »
I've built a few Stirlings, and I have a rotary-displacer LTD unit under construction right now. The seals are the big problem for me.
Here is a video of a small  coffee-cup Stirling that I built a couple of years ago. The power cylinder is graphite, the power piston is aluminum, the displacer is pink construction foam, the working gas is helium in the video, but air is fine too, just less efficient. It will do 600 RPM on a good day, and usually runs for 60-65 minutes on the heat from a cup of hot coffee.
http://www.mediafire.com/?2bmktk95xcx
I'll try to post some pictures of the rotary construction project. I'd like to see other's designs for this too.
Thanks--
Tinsel



Tinsel

That  is a really cool  sterling

Very well built




I had hopes of   using    the heat  from  the  water / plasma     to  drive a sterling .
Judging  by   another thread  ........if  it  can be called  cold fog   there might  not be enough  heat there .

Is there enough heat  released to  capture  with an engine ?
If not ...... I have seen  videos  of  engines   kicking over with water alone .     What would be  driving them ? just  the shock wave?


gary