[jderou]

Phil, I know they are closed systems, but if the crankcase is not vented then the air is going to be compressing on the opposite sides of the piston. I wouldn't think that is a desireable effect.

and I just realized I left the link off. That is the one I was reffering to, Phil.

[pminmo]

jderou,
Couple of links with more info:
http://library.thinkquest.org/C00601...rling.php3?v=2
http://mitglied.lycos.de/PeterFette/howdo.htm
http://www.sesusa.org/StirlingPrimer.htm

[40fordcoupe]

Phil, I know they are closed systems, but if the crankcase is not vented then the air is going to be compressing on the opposite sides of the piston. I wouldn't think that is a desireable effect. Phil

Like at lot of this stuff there is no one answer to fit all situations. For a model Stirling engine it probably won't make a whole lot of difference, that is, unless the engine is designed to run under pressure. If the engine is pressurized then the crankcase should be pressurized too. Phil your theory is correct, but the volume of the crankcase is probably going to be much larger than the swept volume of the engine so the affect is small. In the case of a pressurized engine, let's say we want to run at about 60 pounds of pressure above atmospheric.
If the crankcase is not pressurized than you will have 60 pounds on one side of the piston and atmospheric on the other side. (Also assuming that the seal around the piston is gas tight, which is another problem) OK with a 60 pound differential to overcome on the piston the engine will never run. So a pressurized Stirling must have a closed crankcase so the at rest pressure is equal all around. Before somebody jumps down my throat, yes it is possible to design a pressurized Stirling with and open crankcase, but that gets really complicated. If one gets bitten by the Stirling engine bug and wants to build engines a couple of really good books are The Stirling Engine Manual Vol I and II by Rizzo. Published in the UK they are kind of pricey here in the USA, but IMHO well worth it. :cheers:

[nick.gilling]

All the model stirling engines I have seen have had open cranks therefore vented. I've never seen an engine like the one in the animation to be honest, makes sense though, it should be more efficent than the type I've designed. I would still expect that one to have a vented crank case though.

I am thinking the engines fordcoupe is talking about are much more advanced.

[40fordcoupe]

I am thinking the engines fordcoupe is talking about are much more advanced.

For the record I don't want anybody to think that I'm anything other than an amatuer Stirling engine nut :wave: The problem is that I tend to obsess over these things. Would this or that make a better regenerator? Is a 90 phase difference the best? How much pressure can I run it at? What is the best heat exchanger design? What would make a better thermal trap to prevent heat loss? It can become almost an incurable affliction and I have friends that are living examples to prove it. BTW there are two big groups online. HotAirEngineSociety that is more oriented toward model builders and there is SESUSA which is more engineering oriented, both groups have a lot of very knowledgeable members. :cheers:

[bkinman]

In case anyone here thinks stirling engines are overrated, somebody out there has made millions on a patent that has increased the efficiency of solar panels by at least 30% by arranging the panels into a parabolic array and putting a stirling engine at the focal point of the array. The reflected light of the array powers a stirling motor generator.

[epineh]

Any progress on your engine Nick ? Pictures ?

Russell.

[tim-tbl]

Hi Nick
Think I understand your engine design now, I think that you will have difficulty getting enough cooling on the cold cylinder, pherhaps you could develop a simple water jacket, around the cooling fins, If you are wanting to look at an atmospheric engine, look at the old cornish tin mine pumping engines, so simple but so effective, however I think that you would have to use steam as you need to produce lower air pressure than atmospheric pressure

[nick.gilling]

No more progress yet, I still haven't created the working drawings from the 3D model yet.

Tim, I thought that might be the type of atmospheric engine you were talking about. Newcomens design. The condensing cylinder type Beam Engine. Never really looked into those much but you are right you need a boiler and steam for those.

Nick

[Spin]

I was lookin at your design and I could not find the port where the hot side is conected to the cold side, for heat transfer to occur.
The hot air needs to be cooled to reduce its volume.
Maybe I mist it?

[nick.gilling]

The port is in the support for the displacer cylinder and the bottom of the power cylinder. Will be connnected under the base. Didnt show this on the model as couldn't be bothered. It'll just be a piece of copper pipe. Or what ever works, silicone rubber even.

[jderou]

Does anyone have formulas to optimize stroke, bore, volume for given delta T/hp etc? I found this program yesterday: http://snapburner.home.comcast.net which looks great, but its like $400

[40fordcoupe]

Does anyone have formulas to optimize stroke, bore, volume for given delta T/hp etc? I found this program yesterday: http://snapburner.home.comcast.net which looks great, but its like $400

Take a look at this maybe it will give you a starting point. The price is right.
http://www.bekkoame.ne.jp/~khirata/english/beale.htm
Here is a link description of the "Beale Formula" which gives a quick way to calculate approximate power.
:cheers:

[nick.gilling]

Generally, the ratio of swept volumes is usually about 1.5:1 that is the displacer to power cylinder.

The lower delta T the higher this ratio should be.

It is also best to keep dead space to a minimum, however, not so much so that the clearance between the displacer and it's cylinder is so small it creates too much damping and detracts from the engine's power.

Some general information on here:

http://www.eng.um.edu.mt/~andebo/engines/

[GeorgeAndDragon]

I am also a wannabee in stirling engine modeling. I decided to build one from scratch after assembling two kits. Since I dont have machine shop nor skills in machine shops I realize that the only way for me is to build one creatively from existing canibalized components (not as per drawings). I am from GTA area in Canada, Ontario. I dont know the typical cost of ordering parts from machine shops (tried the emachineshop.com and is too expensive). So far I have all the parts I need for stirling engine concept using household parts. Except piston - bore cylinder which has to be air tight and low friction. However I do not know how to make such accurate part. Any ideas?

[40fordcoupe]

Except piston - bore cylinder which has to be air tight and low friction. However I do not know how to make such accurate part. Any ideas?

I would suggest searching the web for "tin can Stirling plans." Many variations of it have been published over the years and you should be able to download a free set. I have noticed some people have copyrighted it and are selling copies, but a little searching should turn up free sets. Anyway there are several ways people have solved this problem as you will find.
good luck:banana:

[samco]

I also have a burning desire to build a stirling. My plan is for one to put in a focal point of a large mirror dish.

My initial plan would be a 4 cylinger one - with each piston being 45 degrees out of phase of each other. That way - you can use the hot side of one to connect to the cold side fo the next piston. (if I am making sense)

The piston would be double acting in effect - one end would be the hot side and the other would be the cold.

sam

[samco]

oh - my ultimate goal would be a free piston one. (go do a search on nasa's web site)

sam

[40fordcoupe]

My initial plan would be a 4 cylinger one - with each piston being 45 degrees out of phase of each other. That way - you can use the hot side of one to connect to the cold side fo the next piston. (if I am making sense)
oh - my ultimate goal would be a free piston one. (go do a search on nasa's web site)
sam

Ron Steele of Steele's Stirlings offers a set of plans for the 4 cylinder Stirling on the WEB, he also has patent on this confiration. http://www.stirlingsteele.com/Index.html IMHO his design would work very well in a solar dish. BTW I do believe that you need a 90 degree phase difference.

Sun Power in Ohio sells a small free piston Stirling. http://www.sunpower.com/

For the record I have no conection with either company.

[samco]

correct - some how I divided 360 by 4 and got 45 - its been a long day.

BTW I do believe that you need a 90 degree phase difference. .