Why can't I "just buy" a stirling engine?

[Tom Booth]

Basically looks like the "hot" piston has been entirely replaced by a displacer, or perhaps regenerative displacer of some sort, but no longer an Alpha type piston.

Compress_20240424_124014_4623.jpg (31.93 KiB) Viewed 4307 times

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[Stroller]

That's just a gamma schematic. This is the actual engine:

The video I linked earlier shows they're still using the original con-rod on the hot side, coupled to the displacer rod, which runs through a sleeve bearing in the silver cylinder (it will suffer significant side-forces).
Then there's a wire wool stuffed regen cylinder, then the slotted hot cap.

[VincentG]

Looks like a Gamma. Usually the evolution of guys starting with a v twin based Alpha.

[Stroller]

Looks like a Gamma. Usually the evolution of guys starting with a v twin based Alpha.

Yes, I think you're right.

The model they've attached the diesel air heater to is their 1kW 4 cylinder engine. Some of the specs don't add up though. The diesel heater maxes out at 5kW, but the specs call for a 10kW input.
https://tecra.pro/gds1
Screenshot from youtube:


If they really are getting 1kW of electricity out from 10kW of heat input, that's a pretty good result isn't it?

[VincentG]

10% input to electrical output seems pretty darn good from other efforts I've seen.

Those diesel heater are even known to be overrated for output so maybe something is off like you say.

[Stroller]

Yes, my "5kW" Chinese diesel heater actually maxes out at around 3.5kW.
I think it's still at development stage. There's no fuel line going from the tank with the blue cap to the diesel air heater (the fuel inlet joint is between the inlet and exhaust pipe joints at the bottom). Running with no exhaust pipe attached is a bad idea too, it's needed for heat dissipation. The odd thing is that the close up of the control unit at 2:13 does show a running heater. Could have been edited in from later footage I suppose.
https://youtu.be/VI92DJT2s6U?t=133

Another inconsistency is that on the video, they call this one a 'two-chamber gamma version 1kW', whereas the spec sheet says 4 cylinder. Maybe it's two power cylinders plus two displacer cylinders.

I won't be placing an order until the war is over and the sanctions are lifted, so they have time to fix all these anomalies for me.

[Stroller]

Having reviewed a few more of the videos, it's stated that the one-power cylinder gamma engine produces "up to 2kWhr per day". That's a continuous 83.3W, using a hefty propane burner for heat input, and some mild crankcase pressurisation.

Shane Pomeroy's Mk4 diaphragm engine is getting around the same Wattage at atmospheric pressure using a couple of kilos of wood per hour. It's quieter and more fun to watch too.
https://www.youtube.com/watch?v=GB0cd3ZzF3w&t=331s

[VincentG]

Thats too bad but seems to be a common method used to embellish power figures. That puts its output right inline with most builds like that.

[spinningmagnets]

In response to an earlier post in this discussion, I agree that the cold side is less important. The difference between ambient room temperature and a 1500F flame is very close to 1430F degrees.

The difference between 70F ambient room Temps and ice water is may 50F?

That being said, any inexpensive cooling method helps, such as aluminum fins and a flywheel-driven fan.

I am partial to a water jacket plus a thermosiphon tower. If properly constructed, it does not need a pump. Hot water rises in an insulated tube, makes a U-turn, and then flows down an un-insulated tube with aluminum fins.

If the water gets so hot that it begins boiling [*it wont] then the water will never get above 212F, meaning that it will remain much lower than 1500F

Of course we would have to have a system to add water as needed because even warm water will evaporate, rather than reaching steam Temps.

I was curious about air-to-air intercoolers in turbocharged cars, and stumbled across some info about air-to-liquid intercoolers for positive displacement blowers.

I was impressed with how the liquid heat exchangers worked much better than I had expected. And, they worked in hot air in the temperature ranges we find in Stirlings.

[Stroller]

I was impressed with how the liquid heat exchangers worked much better than I had expected. And, they worked in hot air in the temperature ranges we find in Stirlings.

I'm recovering around 450W from the 250C exhaust of my Chinese deisel air heater by running it through the EGR heat exchanger from an old Ford van. The water circuit is pumped with a 12V 5W centrifugal pump and the radiator is a chromed 5' x 30" towel rail in my bathroom. The exhaust gas coming out from the far side of the EGR unit is cool enough to hold your hand directly into the gas flow. The water reaches around 42C.

[staska]

Hello.

I do have a lot of conversation with Victor. He really do try his best to make power producting engine. Because this a product, not a toy, he did limit temperatures and tried to make it as cheap as possible. Hence oil lubrication and air compressor conversion. And slow transmission from finned alumiun bronze heater to welded one.