Stirling engine as college project

Discussion on Stirling or "hot air" engines (all types)
magnustraun
Posts: 5
Joined: Thu Mar 14, 2013 12:56 am
Location: Denmark

Stirling engine as college project

Post by magnustraun »

Hello forum.

We are two students in a technical secondary school in Odense,
Denmark, who are builing a two cylinder stirling engine as a exame
project. We would like to ask you about if you have any experience
building a two cylinder stirling engine, or know about any project
details. Like propertions and ratios, inertia of the flywheel and so
on.

We're designing the stirling engine to work with the temperature
difference 104 fahrenheit(40 kelvin) with two pistons offset from the
flywheel 90 degrees of eachother. Just like the sketch here:
http://www.animatedengines.com/vstirling.html

I hope you will return to us as we are in need of guidance, especially
with ratios and propertions to start building our engine.

Thanks.
Magnus Traun Andersen & Severin Olfred Stolberg-Rohr Hansen.
Odense, Denmark.
Last edited by magnustraun on Fri Mar 15, 2013 2:48 am, edited 2 times in total.
Hopper
Posts: 53
Joined: Fri Feb 08, 2013 6:54 pm

Re: Stirling engine as college project

Post by Hopper »

The type of engine in the animation is an Alpha Stirling engine. Plans for them are hard to find.

You should base your design on an existing model, or at least look at a few existing models to get an idea of the basic design principles.
Here are some starting points:


Jan Ridders' wonderful site. He will email you one set of plans for free, so choose carefully.
http://heetgasmodelbouw.ridders.nu/teke ... rzicht.htm

CAD drawings and more. You need WinZip to open many of them, but I downloaded a PDF of the Ky-Ko Stirling Fan plans without it.
http://grabcad.com/library?page=1&per_p ... ing+engine

Another version of the Ky-Ko Stirling engine is the Moriya fan by Dr Senft is here:
http://courses.washington.edu/me355b/Fa ... iption.pdf

The Ky-Ko is a simple, old fashioned Stirling engine that can be made from common metal stock, no need for graphite pistons and glass tubes etc. It would be simple to turn the Ky-Ko engine on its side, substitute a flywheel for the fan blades and make a nice old fashioned Stirling engine.

Bengs models in Germany. You have to pay for the plans, but not too much. They sell handy material kits too, if you have more money than time to scrounge them up from scrapyards!
http://www.bengs-modellbau.com/material ... /index.php
vamoose
Posts: 267
Joined: Tue Jul 03, 2012 12:16 am
Location: Australia

Re: Stirling engine as college project

Post by vamoose »

Hey guys
That animated engine site is great, It was the first site I came across a few years ago that really got me thinking about how Stirling engines work. (nothing better than a visual stimulus)

I see that you want to build an Alpha type engine. If you don’t have good access to a lathe and workshop, then can i suggest you think about making a Gamma type engine as they are much easier to make using cans, balloons, wire and easy to find components. Also they are much better proven LTD (low temperature differential) engines, as you are using a 40 kelvin temperature difference.

There is a lot of information out there, to sift through, and people on this forum will also help you out. Put some more information on what you have seen and what you are thinking and we will bounce our ideas back at you. It will help to put posts up as you are moving along, so it moves it to the top of the list (and reminds everyone your still here).

Good luck, and keep asking questions...

vamoose
magnustraun
Posts: 5
Joined: Thu Mar 14, 2013 12:56 am
Location: Denmark

Re: Stirling engine as college project

Post by magnustraun »

Thanks for your replies mates! We really appreciate it!

We got a nearly unlimited access to a professional workshop at our school. We also got a big budget around 350$ to spend on all sorts of material that we can get imported in. As you can read that shouldn't be a problem. We are still focused on the alpha engine as it seems to forfill our design needs.

The reason why we are interrested in a low tempature difference is because the engine would be designed to be placed in the ground in a way where the first piston is in the ground getting cooled and the other in the air getting heated. The top piston could fx be surronded by mirrors in a dish-shape to concentrate the sun on the top piston. A stirling engine with the sun as a heating source and the earth as a cooler. This could as we see it work even with a 90 degree angle between the pistons.

We're in the workshop building the engine in week 16 and 17, so we need plans and drawings ready. We would love suggestions and replies especially surronding the ratios and propertions of the engine.

I can't tell you enough how thankful we are for you helpfullness. If you're interested we will upload some images once done.
Hopper
Posts: 53
Joined: Fri Feb 08, 2013 6:54 pm

Re: Stirling engine as college project

Post by Hopper »

Take a look here:
http://diystirlingengine.com/stirling-engine-plans/

Not much plans about for alphas though.

As far as ratios etc go, a standard rule of thumb is that the swept volume of the displacer piston should be about 1.5 times that of the power piston.
Bore and stroke should be about equal.
Bearings should be low friction ball bearings.
Displacer cap and displacer should be stainless steel

and on and on.
Try to get a hold of Dr Senft's book on Stirling Design.

Also if you go to the NASA website they have a downloadable free Stirling Engine Design Manual. (Yes, they use them in spacecraft.)
vamoose
Posts: 267
Joined: Tue Jul 03, 2012 12:16 am
Location: Australia

Re: Stirling engine as college project

Post by vamoose »

Hey Magnus & Severin

Maybe if your up for a field trip it might be worth paying a visit to your Scandinavian brothers and sisters in Sweden.
Kockums – who build Stirling engine powered submarines, and
United Stirling - who are one of the world leaders in stirling engines
(I think ther are affiliated with each other in some ways)
are based in Malmo. (you may already know this).
It would be nice to think that they would be open to students like you guys.

Here's a video you might like:
[youtube]http://www.youtube.com/watch?v=xzpcU41hqAM[/youtube]

Using the ground as a cold thermal sink is a nice idea, especially in a cold country such as Denmark.

I have to say:
In my searches over time I have never come across a true LTD Alpha engine that functions properly (especially with a delta t of 40 kelvin). That is not to say it cant be done, but I think it would be a significant achievement especially for a school project. There are many companies and institutions that over many years have spent the equivalent of many billions of Kronars to fund research done by some of the finest scientific minds on the planet, and they have so far not designed such an engine (to my knowledge).

Maybe some of the guys on the forum will back me up on this point.

On the other hand there are potentially more LTD Gamma engines out there, than there are words in the English (and Danish) language. Some of which can operate with a delta t of only a few degrees.

So I urge you to reconsider you engine design. Whatever design you decide on, with a temperature difference of 40 kelvin you wont get allot of power, but hopefully enough to turn your engine over.


Here is a method of measure that Peter Lynn uses to measure engine success.
http://peterlynnhimself.com/SE_Power_Scale.php
(he is a new zealand inventor and stirling engine enthusiest and also a mentor of Don Clucas who invented the CHP (Combined Heat and Power) Whispergen stirling engine generator)

Image

A quote from Peter
“PS: Having made 14 or so original Stirling engines since 1969, I'm barely averaging Jude 5 so far- and can claim two zero's- one of them just last year.”

Peters stirling page - http://peterlynnhimself.com/Stirling_En ... n_Them.php

Whispergen - http://www.whispergen.com/

So you can see that just getting them working can be a challenge if you deviate too far from conventional understanding and wisdom.

It is easy to get caught up in the excitement when thinking about stirling engines and their possible designs (we've all been there), but can I suggest you spend some more time searching through the forum subjects and the internet before you make a final decision on what type of engine to build for your school assessment.

vamoose
Ian S C
Posts: 2218
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Stirling engine as college project

Post by Ian S C »

On a sunny day with a solar reflector you can expect some very high temperatures, somewhat over 600*C, and possibly quite a bit more, the bigger your reflector the better, within reason. Ian S C
severin
Posts: 6
Joined: Tue Mar 19, 2013 4:55 am

Re: Stirling engine as college project

Post by severin »

Thanks for the replies once again. I'm Severin, the other student in this project.

It's really nice to hear that our temperature difference would go that high, it makes it a lot easier.

We've been looking around on all the stuff you linked us. We're actually considering taking a trip to Malmø, could be really nice. Our school is considering paying for our trip to Malmø.

We've started making sketches in AutoDesk Inventor 2013 of the stirling engine. We will post some sketches here when done. We have not calculated on the ratios and proportions of the sketches properly. With some early drawings at your disposal we would hope that you had some direct pointers to changes we need to make to our sketches.

Thanks for all the help, it's brilliant!
severin
Posts: 6
Joined: Tue Mar 19, 2013 4:55 am

Re: Stirling engine as college project

Post by severin »

Sooo... some posts disappeared after the hacking incident.


Hopper, we have trouble opening your links, could you maybe resend them?



Still thanks for the help, we're sending in a material list to our school today.
Ian S C
Posts: 2218
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Stirling engine as college project

Post by Ian S C »

A good person to contact is Chriske in Belgium, hes a teacher, and his class produce excelent Stirling Engines, and before the crash he offered plans, hes a regular on this site, and there is a thread just down the page titled Stirling Engines-School Projects. Ian S C
vamoose
Posts: 267
Joined: Tue Jul 03, 2012 12:16 am
Location: Australia

Re: Stirling engine as college project

Post by vamoose »

I'll throw this in on Hoppers behalf. The links should be unbroken...
Its from the Website Links Area of the forum. If you've got time have a bit of a look through it, there might be some things of interest in there for you guys.
Hopper wrote:
Jan Ridders' wonderful site. He will email you one set of plans for free, so choose carefully.
http://heetgasmodelbouw.ridders.nu/teke ... rzicht.htm

CAD drawings and more. You need WinZip to open many of them, but I downloaded a PDF of the Ky-Ko Stirling Fan plans without it.
http://grabcad.com/library?page=1&per_p ... ing+engine

Another version of the Ky-Ko Stirling engine fan by Dr Senft is here:
http://courses.washington.edu/me355b/Fa ... iption.pdf
The Ky-Ko is a simple, old fashioned Stirling engine that can be made from common metal stock, no need for graphite pistons and glass tubes etc. It would be simple to turn the Ky-Ko engine on its side, substitute a flywheel for the fan blades and make a nice old fashioned Stirling engine.

Bengs models in Germany. You have to pay for the plans, but not too much. They sell handy material kits too, if you have more money than time to scrounge them up from scrapyards!
http://www.bengs-modellbau.com/material ... /index.php
Last edited by vamoose on Mon Apr 08, 2013 6:03 am, edited 1 time in total.
Chriske
Posts: 87
Joined: Sat Oct 02, 2010 1:24 am

Re: Stirling engine as college project

Post by Chriske »

Hi guys,

I would not advise GrabCad to download plans/drawings from. I did download and found out that a lot of these engines (drawings) were not complete. I told the administrator about this problem but I got no answer from these guys. To verify download the STP or STEP files from these engines and open them in any CAD program, you'll see. Pity...!

I would absolutely advice Jan Ridders' site. ( http://www.youtube.com/user/HEETGAS ) We made a few of his engines and they all work.
Last one Mathieu that was made in our school (for his final exam) was this one :
http://www.youtube.com/watch?v=ERqlqYIUIzg
In ran an amazing speed of over 1000 rpm...!

But as I read in your post you wanted to make a 2 cylinder, so I can provide you drawings of my own engine. Last year we made a Stirling only on cylinder, this year we made basically the same but this time 2 cylinders. It's a relatively powerful little thing and will run as fast as 1100 rpm. Driving itself (in our case) on track gauge 1.
Drawings all in metric.
This is the one (without wheels) : http://www.youtube.com/watch?v=tVInE4VCDX4
This is the our 1 cylinder riding our track during open door in our school may 2012 : http://www.youtube.com/watch?v=vQAP9XQGnLY

Whatever you do GOOD LUCK...!

Chris
Mijn thuis is waar mijn draaibank staat...
severin
Posts: 6
Joined: Tue Mar 19, 2013 4:55 am

Re: Stirling engine as college project

Post by severin »

Wow thanks guys.

Chriske, what kind of school are you teaching in? It's sound awesome, but have you got any experience with a 90 degree 2 cylinder stirling engine, a vstirling? Like this: http://www.animatedengines.com/vstirling.html

We have collected all the steel we need for the engine now, we're starting construction tomorrow.

Here are our drawings if it could interest you :), they are in metric (mm):
http://olfred.org/arbejdstegninger.zip

We're using 110mm pistons that we're getting shipped in from China.

Have anyone got any knowledge about ratios of stroke length, or weight distribution of the flywheel?


Thanks again for all the help! We couldn't do this without you! :)
Ian S C
Posts: 2218
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Stirling engine as college project

Post by Ian S C »

You didn't pick the simplest motor to build, but if its not your first. What are your pistons made of, and how are you going to modify the hot piston ie Heylandt Crown (not shown in the animation). With a motor that size you might need about 200 mm to 300 mm diameter for the flywheel.
With a motor that size I woul think of using about 50 mm stroke.
You will need to build a little furnace to enclose the fire, and consentrate the heat around the hot end. Ian S C
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