Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations KootK on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Stirling Engine No Pressure

Status
Not open for further replies.
Replies continue below

Recommended for you

Sort by date Sort by votes
The LTD engines I've seen have a diaphragm seal on the power piston, does yours?
 
Upvote 0 Downvote
Thank you for helping me on this project.
The videos below is to clarify Diaphragm.
I would like some advise on how to source diaphragm part.

1st mostly likely the power piston

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/video/upload/v1698255497/tips/20231025_172718000_iOS_l5hthc.mov[/url]

2nd video if you mean displacer is the "power piston"

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/video/upload/v1698256254/tips/20231025_174254000_iOS_qcwpx8.mov[/url]
 
Upvote 0 Downvote
Your first video shows the smaller (power) piston, and it's this one you may want to try sealing.

So, with a LTD (low temperature differential) engine, you don't have a lot of pressure difference to work with to drive the power piston. The seal you can achieve with a loose slip-fit on the
(brass?) piston sliding in an (aluminum?) bore is not going to be great (and thermal expansion of the different materials plays hob with the sealing as well. Test this - if you plug the port with your thumb and let the piston drop under gravity, it should take several seconds (10 or more) for the piston to drop out of the cylinder. Even that is just not good enough to get sufficient work out of the gas to keep the engine ticking over. The engine probably will work better if you put it over an open flame, and get the hot side temperature up over about 300 or 350 F. Designs I have seen that work on a cup of hot water use something like a piece of rubber balloon to seal it off; you could play with that idea on your engine and see if it helps.

But you also have a lot of potential heat leakage (conduction loss) from your engine along the displacement cylinder wall, you might try making the 4 posts holding the hot and cold plates much thinner, or hollow with thin walls, or from a very non-heat-conductive material (titanium? Hah. Plastics would likely work).

Check these two guys out - low temp. diff engines. Jan Ridder's engines (I've built several of his designs, but not the LTD Stirling...yet :) work extremely well if you follow his drawings carefully, or at least follow his engineering intent, which he does a good job of explaining. His LTD engine uses a graphite piston in a glass cylinder, which can be machined and polished to achieve a very good seal, and both materials have near-zero thermal expansion, so the seal stays the same from room temperature to operating temp. And that engine can work from the heat of your hand in a cool room...pretty nifty. Myfordboy also has plans for a LTD coffee-cup engine that works well, he uses a balloon seal I think. Lots of other info out there, see sites like the ones ive posted and follow their links.

Jan Ridders site - Myfordboy YouTube site - also sites like this have members that love to help people build model engines (like 1/8 scale Ford 302 V8's and such) -
 
Upvote 0 Downvote
2 minutes 42 seconds 61 microsecounds to top into bottom piston
 
Upvote 0 Downvote
That might be too tight - i.e. causing simple friction to slow the engine down. But try testing with the piston suspended from the plate, i.e. gravity pulling the piston out of the hole, this is the more typical test for the 10 second rule.
 
Upvote 0 Downvote
Doing what you said about modifications.
In the meantime would it be safe to run under a open flame candle? (more heat?)
 
Upvote 0 Downvote
Running over a candle flame safe? - I would think so. You may want a temperature sensor on the base plate to monitor it and not let it get too hot (stay below perhaps 350 deg. F?); getting that hot might mean more than just a candle, perhaps an alcohol burner. 350F is conservative, but assumes adhesives and/or sealants are used in the construction, e.g. loctite or silicone.

Measuring the temperature of the bottom and top plates, and correlating that to the speed of rotation is what Jan Ridders does on his LTD page, and is an ad-hoc power vs. temperature differential curve, seems pretty informative.
 
Upvote 0 Downvote
btrueblood.

Thank you for your help with Stirling engine.

I made a diaphragm seal with a rubber glove and it help get the machine moving.
The problem that I have to solve now is how to get it to more faster and more consistent.
I don't have the machinery to do what you recommended of "thinning" out the bottom plate of the Stirling engine. Today I like to propose an alternative coffee cups use foam to keep coffee hot. Why not use some foam I have sitting around and make a "new" bottom plate out of foam?

What's your thoughts?

Matthew Monti

 
Upvote 0 Downvote
Good job getting it running, Matthew. Faster/more power means a bigger temperature differential, and yes, there are people who have mapped the power output (it will be in the milliwatt range, so might take a few weeks to fully charge a phone?) Stirlings tend to have low power output unless of a sealed, high pressure design - see NASA archives for a design/prototype/demonstration of an automotive powerplant, the free-piston stirling if I recall correctly.
 
Upvote 0 Downvote
Let me change gears with you beyond the obvious problems with using a Stirling engine I own run on this power.
The concept that I am really after is can you make a stirling engine work using the process that occurring in the following video. (this is concept and as I can see from my "knowledge" I don't have an engineering degree. I a simply looking at this from a point of view of someone with has a hobby for engines.




Matthew Monti (Student)(OP)6 Dec 23 16:17
The link above shows a hot coffee heated by metal reacting to heat being moved around in sand. Sand deep enough traps different temperatures depending on the time of day. My theory is can you make a stirling engine where you use the process used in Turkish coffee to make a stirling engine that powered by geothermal temperatures. The temperature difference would then generate movement and thus "electricity". This is my idea.
 
Upvote 0 Downvote
Um, possibly. But you could use any heat engine, or a thermopile, since you have theoretically located two thermal masses to derive power from.

But, sand works for Turkish coffee because it's very hot, and the small pot is moved through the sand to improve heat transfer rate. There is a fire under the sand bed keeping the sand hot.

In reality, sand is a fairly good insulator (well, relative to metal), and transferring heat into and out of a sand bed would be tricky...though google fluidized beds for ways you could make it work. There are other ways people are extracting geothermal heat for power generation. Iceland does it fairly well, so does New Zealand...both use existing water sources and/or injected water as the heat transfer medium.
 
Upvote 0 Downvote
btrueblood thanks for your answers and help and keep you posted on progress and more edu on Engineering.
 
Upvote 0 Downvote
I was looking at wind farms. I learned about how they convert lower RPM rotation of large blades and "convert" the lower rpm to the "higher" rpm for electricity. For this engine I am creating I like to learn more about this engine works and any resources will be appreciated. After all am very skeptical that I am wrong on that fact as it would be hard to find winds that meet over 1800 rpm ?! Maybe a tornado or hurricane but not wind you see daily. Perhaps this can be reimagined into stirling. Of course this would be expensive and have to be machined (no amazon or ebay parts). I don't know if this can be applied to stirling engine as even the modern marvels engine video showed use of steam turbines and NOT piston engines with high rpm for power generation. (Larger Power Engine idea - in progress)

Second idea steam powered portable device to use for power generation phones in case of emergency from a tea kettle. This would NOT be stirling powered.A device like this would be used in emergies or when camping where you don't have access to electricity. A device would be nice for long term emergies where access to daily good hard. Same reason you still see kerosine lamps sold despite better technology (more light and hrs ). Looking at small steam turbine engine. Think about it long term usage (batteries age and break bad emergencies). Solar powered phone charge up only work when weather pending (bad for emergencies).
 
Upvote 0 Downvote
sorry, but sigh.

yes, wind turbines turn at a very slow speed, obviously, something approaching 0.1 Hz. [edit] ... well large turbines do, small turbines can have a much higher frequency, maybe 1 Hz, but still much lower than mains power.
The the generator attached to the blades is therefore producing electricity with a very low frequency.
This frequency is stepped up to a conventional power frequency (50/60 Hz) using a transformer ... no magic.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.
 
Upvote 0 Downvote
Think about it long term usage (batteries age and break bad emergencies). Solar powered phone charge up only work when weather pending (bad for emergencies).
Click to expand...

You're going to carry around a can of white gas, stove, water pot, and generator to replace a few 18650 cells?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
Upvote 0 Downvote
A good plan violently executed now is better than a perfect plan executed next week. Paton

My idea for steam power generator seem to bulky, slow and expensive.

This product below is on the market and does a better job and is portable. Good in area where power generation is none or unreliable Gaza, Ukraine or natural disaster. Solar power and when no sunlight has power crank also it small and portable.

 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Matthew Monti
  • Locked
  • Question
Stirling Run on Electricity
2
Replies
28
Views
103
Matthew Monti
Matthew Monti
sunil108
  • Locked
  • Question
WHY Bearing pad not provided to skirt in vertical pressure vessel?
Replies
0
Views
44
sunil108
sunil108
S1mul4t0r101
  • Locked
  • Question
Enormous pressure values in Abaqus
Replies
0
Views
90
S1mul4t0r101
S1mul4t0r101
Student212
  • Locked
  • Question
Pressure purging or dilution purging
Replies
5
Views
56
waross
waross
s white
  • Question
Need to confirm Residual Pressure with Hyd Calcs
Replies
0
Views
56
s white
s white

Part and Inventory Search

Sponsor

Back
Top Bottom