Stirling Engine Generator Mk4 (Rocket Stove!) Part 10
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- เผยแพร่เมื่อ 29 ก.ย. 2024
- Building of an easy, cheap and reliable, DIY stirling engine full size model! It will be fired by wood and could be a great stirlingkit if it works!
This is a fun engineering project that I will use to power a generator to provide energy. It will use an efficient rocket stove that burns really hot using wood that will hopefully drive it at great speed! This technology can use any fuel type with the correct burner so is dual fuel as well. I would like to provide plans / stirling engine kit for DIY builds and possibly build machines too.
This is all pivots on being able to produce an easy, cheap and reliable stirling engine! Watch this space…..
• Stirling Engine Genera...
This video
I'm on a mission to solve the hot side diaphragm woes! My father has been burning the midnight oil and has come up with Kevlar as a potential alternative. The Kevlar we got is quite thin so I layered it up 4 X with silicon sealant in between. I also made a few other subtle changes to try to refine the engine.
Success! The engine ran for 4 hours without even a murmur of the hot diaphragm failing but only time will tell how long it will last. The engine ran extremely silently with the only real noise coming from some metal to metal contact on a bearing spacer (easily solved).
Power output was less impressive at 45w and I am starting to think that the hot heat exchanger might not be collecting enough heat. This could be because the flue gases are bypassing a lot of it or it might be the flue gases can't transfer enough heat through convection. I was made aware a few months back about the difference between radiant heat (efficient) and convection heat (less so).
Anyway, my hopes are still high because there are still a few things I can try to improve things.
All the best
Thanks for watching
shanepomeroy@hotmail.co.uk
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Well Shane, you never cease to amaze me how you have this innate ability to think outside of the box.
I am enjoying following your progress with this model, as I dare say many others are too.
Keep up the good work, and I most certainly look forward to your next tweak.
Brian from NZ
Nice to see some good progress on the little engine. Thanks for sharing I'll be waiting for their video!
I was surprised at the quietness of the new seals! Excellent results on a tough problem that you have solved. Good hints from others on the insert for the tubes.
Yes, perhaps the hot side needs to see the direct heat from some other design of a stove, or maybe try some coal just to see if the higher heat value of coal in the fire would be an indicator that another type of stove is needed.
Enjoying the adventure!
Hi Greg, I think I'll try some coal next video to get that direct radiant heat. I think that is probably the number one issue with this engine, cheers
Bravo. There are nice effects and the quiet operation of the engine. Regards
Great, now with the diaphragm problem out of the way you'll be able to focus in increasing power.
I believe that if you pipe the intake air through a steel tube inside the smokestack, preheating it before feed into the furnace, you'll have a hotter flame.
To pressurize the engine will help too
Success! Great to see that your seals are working! And that you were able to reduce the noise.
Were you able to get a compression ratio since you modified the hot side?
Is it the frictional drag from cold to hot side that is eating up the energy? For stationary applications might it work to design for very large volume and very low speed to reduce those losses?
At 6:36 I think you mean kevlar, not teflon, yes?
Ah, whoops! Good call : )
The design of your engine set is similar to this one
th-cam.com/video/bQ1wOIsrEUA/w-d-xo.html
I've seen that one! It probably inspired me in some way
There seems no getting away from the challenges of gas seals of the hot end - I see a Mk 5 reverting to a displacer-type Stirling to remove hot end seal issues - that could throw up possibilities of compression and even hydrogen lol
I would be very curious for you to measure the output at the same RPM with and without the elastic. My gut feeling tells me there is some sort of loss happening from it. Can't seem to rationalize it though 😊
Nice job, congratulation!
Low tech stuff a bunch of copper wool in the exchangers, higher tech add some heat pipes. Cut down your volume increase your surface area
As you shrink the volume in the exchangers you will see the temperature even out. It's the dead air. It's the age old problem how lower volume without increasing pressure.
So rubber band thingy did worked as expected :)
Sadly you did not add any pressure into it. 0.2 bar would really make some improvement, and would answer question - as we are lack on heat transfer, or lack of working fluid volume.
Ps - max rpm - produced power equals fluid (pressure) losses of working in heat exchangers/regenerator. Heat transfer is kind of similar per time, just cycles are shorter. It is slightly improved by higher airflow, but only on inside.
Always excited to see a new video, great progress mate!
Very nice work! That is a beautifully simple stirling engine. Unfortunately they never were known for producing much power.
Maybe it's time to look at the Newcomen design, which has been completely forgotten. Thomas Newcomen built them beginning in 1772 so it's about as simple as things get, and they lasted for decades. No risk of steam explosion whatsoever, and a 2 piston oscillating cylinder with a flywheel could be very smooth.
see th-cam.com/video/GMgP-4O99qU/w-d-xo.html and th-cam.com/video/Yu-HN7GEBe0/w-d-xo.html
45 Watts may sound puny but it definitely proves as a working light scale model. Maybe without blowing it up, what could you generate if there was a rocket or a gentle air blower for a hotter fire?
God, I think we're gonna need these soon when services like an electricity grids fall apart and grow even more prohibitively expensive ...
Why not just replace the diaphragm pump with a small roots blower? It'll probably move a lot more air and have longer-term reliability.
Im just going to suggest some random engine I found on TH-cam that you should try instead. I've never built anything and you have but I still know better..
Are you loosing power because the engine is spending so much energy rocking back and forth on the wheels? Would make for an interesting test.
On a later version, can you put a valve system on the heat exchanger so that the air circulates only in one direction? Like two one-way valves on the hot side. One going in, and one going out.
Another thing to consider is how quickly and how much the volume of air expands and contracts. You would want to size your piston size and stroke based on that, and your engine speed will have an optimal RPM.
You are getting good heat transfer from the rocket stove at the hot end as displayed on your temp gauge. Your crank throw is very small and the piston stoke is also quite small! Maybe you would benefit from having pressure gauge at each end! That way you could calculate what pressure is pushing on the diagram and what Force is acting on the connecting rod. If the pressure acting inside is high you know your losses ate in your mechanism. If the pressure is low, you know your losses are in the construction of the diaphragms.
I also would replace that mesh fence inside the regenerator for something like wire wool or try a good insulator like fiberglass fiber?
What about a simple damper in the flue above the heat exchanger to hold or slow down the hot gases escaping into the air.
Volumetric heat capacitity make iron and stainless steel great for regenerator. But I'm wondering if its not so great thermal conductivity is restricting the rate of heat flow in the rocjet stove and the radiator. What if you used copper tubes for the thermal transfer section and stainless steel pipes for the regenerator portion of the tubes? Futhermore, i dont think you want to loose heat in the regenerator section. Maybe you can insulate that easilly and test if it makes a difference.
I can't wait till you try and run it backards as a heat pump.
When are you planning to put some counter weight to get better balnce?
Have you considered using oiled leather for the seals?
Okay I didn't want to say this because I was going to do this myself but if it will help you why not liquid Pistons liquid Pistons I believe is the way to go when it comes to the Sterling engines
Were you really going to do it though? Even liquid piston hasn't done it.
@@jerbear7952 yes I need to eventually I don't know what you mean by liquid Pistons I haven't done it
It is baffling - changing more than one thing at a time makes it difficult to attribute what impact each has if any - I felt sure you would be rewarded with at least double the power - One thing I noticed was the air has passed through the first half of the cooling passages its job was mostly done - the last half is a lot of dead space for a little temperature change.
Your quite right but I am much to impatient: ). The diaphragms are still quite puffy which I think I can solve. I think the biggest limiter is the lack of radiant heat at the heat exchanger, cheers
@@ShanePomeroy Can you corrugate the mesh inserts so they alternate touch the sides of the transfer passages so they conduct the heat better - I thought perhaps pass them through a loosely meshed pair of spur gears till they spring against the walls needing to be pulled through the passages with some force?
Thank You Shane!
Chuck, watching you from Jensen Beach Florida.
Very nice!
Maybe more pressure inside the engine?
I had a big smile on my face when I saw the Kevlar did not fail
Great job keep it going
Hello Shane, very good for the progress, cheers.
Glad to see that the carbon fiber did the trick. Cheers.
That is a sweet running machine. Watts aside, I'm sure you can do plenty of stuff with that engine. Maybe a pump to actively cool your cold end? You could do lots of mechanical work besides the electrical output. Please keep it up, you are doing great work here.
Actively cooling the cold side might be a wash. The efficiency is determined by the difference in temperature between the hot and cold sides, so you're effectively using some of the engines power to make the engine more efficient. Therefore... A wash, unless you use that heat to perhaps warm a cold room ...
I have a gamma model diaphragm piston. the good thing is that it doesn't get hot, it's been there sometimes for a day charging the batteries and it will probably never stop running
Sounds interesting, how big is your engine? I'm assuming a fair size if it's charging batteries : )
Ayy! That diaphragm is looking wayy better! Exactly the construction you needed.
For power, you might want to try Increasing the pressure now since that is guaranteed to increase the power, you might be able to do 3bar or so with your new diaphragms. In fact the limiting factor might now be your tubes and the linkage arms.
You could insulate a longer length of your tubes to make more of a regenerator too, up to that first bulkhead seems like it would be good. You want the regenerator to be able to capture most of the heat energy in the air, currently yours is far too short for that.
If you ever have to make new diaphragms you might want to try making them thinner. You only need enough cloth to prevent it bursting, adding more thickness will just make it stiffer and could actually lead to it wearing faster, especially if it is getting creased or such.
Thanks Sam, great advice : )
Did you try to increase pressure of air???
If you can make pressure about 10 bar, it cause increasing of power to 400 watts - it is enough to drive 100kg stirling car + 100 kg passenger.
Hydraulic drive wheel from stirling pump - it might be reality.
Have you considered using helium in the engine under pressure ?
Also presurizing the back side of the diaphragm to create back pressure so that your not working against atmospheric pressure. Higher pressure will yield more power
Hi Perry, Pressurisation might be an option now the seals are lasting longer. It would probably be something I'd include on the next engine. Many thanks
I'd consider using pistons if I were you. The diaphragm is a dead end. It only works on a small scale.
Why is small scale a dead end
not much power when taking account of the total amount of heat.. maybe better piston stirling instead of membrane at diy level. anyway nice machine to see^^ the next one u do a ross yoke ? :)
go smaler and go pressurise wath u want up to 8 bar ^^ (car compressor XD) ross yoke more easy to presurise the crankcase (recover ebike brushless motor for power gen and starting, all encose inside 2 atm of helium i wana see XD) maybe take inspiration of the torino engine, lot of small coper tube for heat exchange, with lighter gas it gonna flow well ^^
I wonder how much did you pay for the metal cutouts because nowadays you can buy a desktop CNC machine for around $300
Not that cuts steel like that
Lots good ideas in this test.
Good show old chap !!
Kár hogy nincs magyar felirat!
Thanks so much for your content! I've really been enjoying your ongoing development of this engine.
Having said that, it's a mathematical certainty that the upper limit of the power output of this engine is always going to be bounded by the pressure of the air charge inside the engine. And the operating pressure, at present, is limited by your choice of diaphragm-style displacers in lieu of more conventional pistons.
Up to this point, you've been operating the engine at near-atmospheric pressure. If you were to substitute the diaphragms with true sliding pistons, you might be able to realize an engine capable of sustaining an operating air charge significantly above ambient pressure - which would greatly increase the power output without changing any other operational parameters of the engine.
I really like your design .. been watching your channel for a while .. and glad to see you continuing to improve the engine!
Much quieter and smoother this time! I suggest some type of water cooling to give more power.
For extra power what about using helium instead of air as the working gas?
Have you thought for even a second about the amount of complexity that would involve for the return? Engineers need to be practical.
@@jerbear7952 if it's a sealed pressurized system how would it need to be complex? If it's not sealed i suppose that wouldn't be simple.
You’re really sorting this thing out. Great work.
Shane, great project you have there.
However, the Stirling Engine, from the beginning, was never efficient. At least your engine can produce 45 Watts of electricity. Most produce just enough energy to run itself.
I propose that you convert this machine to boil water. Make a boiler or use copper or stainless steel tubes.
You can make a steam engine or you can buy one on line,
I think you could generate about 10 times more power (450 W) than the Stirling engine for the same amount of wood 🙂
I think mild steel pipes with Around 26 - 37 W/(m·K) thermal transfer is a potential limiting issue where as copper is about 398 W/(m·K)
Q = - k * A * (ΔT) / L
Where:
Q - Heat transfer rate (watts)
k - Thermal conductivity (W/(m·K))
A - Surface area (square meters)
ΔT (delta T) - Temperature difference (Kelvin) between the hot and cold sides
L - Distance (thickness) of the material (meters)
Also, the pressure of the working fluid (air) is limiting the maximum power. Available in the stirling cycle loop.
@@kreynolds1123 Hmm, it looks like you're in front of me.
It would be interesting to see how much more electrical energy you could generate with a steam engine burning the same amount of wood compared to the Stirling engine.
@@Rose-f2t my guess is that it would be easyer to build a steam engine to produce more power. But one thing I like about stirling engines that the cycle can be reversed and used as a heat pump.
I missed the meaning in "you're out in front of me". Please explain it in other words.
These are great changes very creative 👍🏼
Congratulations on a good run.
Hmmm so quiet. Great job so far.