Absurdly simple thermoacoustic-steam "rice" engine – What's going on here?

[Daemon]

Any ways, I'm still trying to pin down the physics of this system. I feel like I need to make a piston model to really understand what's going on and what kind of forces are involved.

Is it concussion from steam explosions?
Is the boil more isothermal?
Does the boiling cease on the return stroke or does it continue?

So many questions.

[Tom Booth]

Any ways, I'm still trying to pin down the physics of this system....

So many questions.

Earlier you wrote: "I made an observation due to following a recommendation from one of the youtubers..."

Have you posted videos? Do you have a YouTube channel?

It looks like all of your previous posts were deleted with that account. Can you post, or repost the link to your YouTube channel please?

[Daemon]

Yeah sure, I'm on vacation over seas atm, but I'm taking some time to work on it. I've got a mill, lathe and a few engineers from Siemens here interested in helping me get a piston model running. So I'll probably have some great insights to post to my channel next week.

[Tom Booth]

Yeah sure, I'm on vacation over seas atm, but I'm taking some time to work on it. I've got a mill, lathe and a few engineers from Siemens here interested in helping me get a piston model running. So I'll probably have some great insights to post to my channel next week.

Thanks, sounds great, I was just interested in seeing the engine that you were running on tea candles that ran so powerful so quickly you had to use fewer candles. I missed that. Or the one that was welded.

Or maybe your self running refrigerator that doesn't need fuel and reaches absolute zero.

[Daemon]

https://m.youtube.com/shorts/RXHhnu-_b68

That's back to my channel, I've only got the one video posted on it now, I'll have a nicer video when I have something nicer to show off.

[Daemon]

I should point out, the unit on candles didn't "run so powerful so quickly I had to use fewer candle" rather, it ran with a lot of power on 2 candles but I was reaching thermal overload quickly because I welded with solder and I was using glass beads.

Now that I have copper BB's in there I don't reach thermal overload.

I only made one so far and it's still welded, but I'm going to make a piston model this week, time permitting.

The video I have up now is old, that was my first run.

[Tom Booth]

https://m.youtube.com/shorts/RXHhnu-_b68

That's back to my channel, I've only got the one video posted on it now, I'll have a nicer video when I have something nicer to show off.

Thanks, I do remember seeing that video. Seems like a rather strong, steady running engine. Was that using rice or something else?

[Tom Booth]

Anyway, I think, because a while back the forum owner was having difficulty keeping up with the spam bots so set the forum to automatically delete posts when reported, along with the suspect account. He may not even be aware of the situation. If you sent a PM to "Administrator" explaining what happened he may be able to restore the deleted posts & account.

[Daemon]

https://m.youtube.com/shorts/RXHhnu-_b68

That's back to my channel, I've only got the one video posted on it now, I'll have a nicer video when I have something nicer to show off.

Thanks, I do remember seeing that video. Seems like a rather strong, steady running engine. Was that using rice or something else?

That one was running with rice, the rice works well while it works. Unfortunately, it's a limited time run with rice because you eventually cook all the rice lol.

I was laughing about making a novelty rice maker with this.
"When the nut stops shaking, the rice is done making" XD

[Tom Booth]

Yeah sure, I'm on vacation over seas atm, ...

Are you still away on vacation?

I'm very much looking forward to any more videos. You mentioned on the other thread, a slow motion video showing explosions?

I imagine suspended water droplets exploding into steam vapor?

[tenbitcomb]

> Is it concussion from steam explosions?

I don't think so. The engine will continue running despite a lack of boiling once it's been removed from the heat. In my experience, it may do this anywhere from 10 seconds to even a minute. Honestly, I think the boiling and steam flashes are a red herring. If the boiling was doing anything but facilitating heat transfer via water vapor, the engine would be less stable (boiling being chaotic) and it would stop immediately when boiling stops.

Steam explosions only seem to make any difference during the initial stage of the cycle, likely because there isn't enough water vapor in the air at that point. During maximal performance, steam explosions can be heard due to the dripping of condensation from the stack back into the boiler, and this may or may not have a noticeable impact on performance. Once it's going, variations in steam seem to matter little and flashes of steam don't seem at all critical for operation.

> Does the boiling cease on the return stroke or does it continue?

Maybe it has some effect like that, but for the same reason I mentioned above, I doubt it really matters. At best, it may be assisting the engine operation but doesn't make or break it.

[Tom Booth]

I was very impressed with this engine also:

https://youtu.be/r9lYsW0Df08

Which, I would argue, is constructed in a way similar to the rice engine, having a stationary regenerator but no moving displacer. Though there is an inner membrane that helps move air through the regenerator. It could be argued that this inner diaphragm serves a purpose similar to a displacer. There is also only a balloon power piston.

But what I wanted to say is that I've been wondering off and on whenever I'm reminded of it, since 2006 at least:.

viewtopic.php?f=1&t=77&start=15#p174

If some DIY engines that run very powerfully depend on a very humid environment.

If a person happens to live in some location like Seattle Washington where it rains almost all the time or there is naturally very high humidity. There may already be considerable moisture trapped inside the engine from the time it was constructed.

Considering the expansion ratio of 1700 X it would not really take much moisture to have some effect.

When I considered the idea of using some alternative substance that would boil at lower temperature, maybe even at ambient ("room temperature) Looking over the chart at engineering toolbox and the like I found an ideal candidate. Boils at room temperature, Non-Flammable,... The same stuff once used in the perpetual drinking bird toy, before it's manufacture was banned.

Trichlorofluoromethane R-11 refrigerant

Boy did that get my conspiracy theory wheels turning.

The substitute fluid now used in the bird methylene chloride has a much higher boiling point, so does not work as well as actual Freon.

There are a few other things that might work, though it seems nearly all are ether banned (some similar type refrigerant) or would be more dangerous, being flammable or highly toxic.

[tenbitcomb]

My guess is Tristan's engine isn't thermoacoustic but is actually an alpha Stirling engine.

Here's the video where he shows the internal workings:
https://www.youtube.com/watch?v=CXsFNPmjluo

(curse YouTube for continuing to make finding old videos an incredible pain)

I don't know why he called it a "thermoacoustic stirling" since it's not really displaying any behavior that's specifically thermoacoustic. There's at least two reasons to believe it's not thermoacoustic:

1. There's a crankshaft of sorts to control the piston offset.
2. It operates at variable frequencies rather than a single frequency.

Maybe he was just fresh to the idea of thermoacoustics at the time. It just doesn't seem like an alpha engine to the naked eye because almost every alpha configuration is shown to be two distinct cylinders connected by a regenerative stack. Tristan's engine has the hot end piston inside the cylinder rather than on the outside, and the regenerator is simply wrapped around the hot piston; the piston action pushes air down and up through the regenerator. Technically yes, the air is being displaced, but this doesn't appear to be novel in contrast to what happens in an alpha configuration.

I believe said this already somewhere on here, but my theory is that a lot of these "thermoacoustic" engines on YouTube that have a diaphragm on the inside with no displacer are actually alpha engines. The neat thing about them is they show that an alpha configuration with diaphragms is not only possible but even better performing than most betas and gammas.

The one thing we can't really know about Tristan's engine is whether the hot end components are staying in place or moving freely. It's possible that they're at least somewhat moving freely, which seems to be possibly optimal for the Stirling cycle but could also mess up the timing unless that's something he corrected for. However, I don't see any reason to believe that an alpha without that secondary displacement feature couldn't work.

To your point, I imagine that local conditions can have a significant impact on the performance of both Stirling and thermoacoustic engines. Who knows, maybe someone living in the middle of the Amazon rain forest doesn't even need to add water to their thermoacoustic engine. haha And perhaps some Stirling engines might have trouble performing under humid conditions without adjustment. LTDs would probably be the most impacted by humidity if I were to make a guess (having owned a few and finding them to be strangely stubborn).

[tenbitcomb]

> Trichlorofluoromethane R-11 refrigerant

One problem that almost any alternative fluid introduces is the need to always keep the engine totally sealed, given that these fluids are usually either poisonous or flammable or both. The nice thing about water is it's plentiful and nontoxic, therefore it doesn't really matter if the engine allows a small amount of vapor to escape. Although pressure buildup barely seems to matter during full operation of the engine, it does matter during warmup and heat overload. A valve can somewhat solve this, but it still means that potentially expensive fluid to be lost over time, and I imagine there's no safe amount of R-11 refrigerant, freon, or ammonia to inhale. R-11 becomes phosphene gas when burned, so... yeah... I don't think I'll be trying it any time soon.

However, an industrial/research/scientific grade version of our wet thermoacoustic engine might be able to be engineered such that it can use R-11 and not pose a hazard. After all, A/C units are able to use R-11 without being an everyday hazard. I just don't think I have the skill or resources to build something up to that specification.

The closest might be a water-alcohol solution since a concentration ~30% isn't really flammable. Phase separation could make it flammable, but probably not at the source of heat but on the end furthest away.

[tenbitcomb]

Yeah sure, I'm on vacation over seas atm, but I'm taking some time to work on it. I've got a mill, lathe and a few engineers from Siemens here interested in helping me get a piston model running. So I'll probably have some great insights to post to my channel next week.

Awesome! I recently tried using a piston that I harvested from a tire inflator from Harbor Freight, but I'm pretty sure the fit is too tight and that it needs a flywheel or a spring.