J. Phil Thien's Projects

There are industrial size ones too, see the last page of http://www.enviroheatuk.com/files/brochure%20UK.pdf. 8 inch hose and 5 feet diameter for the cyclone, yikes!

Oh, of course, silly me  :D

What's a "moter"?

The ash cyclone with bucket and heat resistant hose is SEK 956. Not cheap.

Yes, I'm in Sweden. The retailers are too far from me, I can tell from the retailer map on the swedish pages. :( For me it's probably simplest to call the manufacturer directly, but email would be an option I guess. I wonder what they charge for the transport...

Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
The turbulence isn't there because of the baffle, the baffle is there because of the turbulence.

I agree with you on this, perhaps I was unclear in the previous comment.

Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
The turbulence exists in the VV design, too (incoming air running into an already spinning air mass causes turbulence).  The designer of the VV just didn't do enough to address it (IMHO).

There certainly is turbulence there too, but I think that he has put some thought into this. He went about solving this differently (IMHO).

Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
"Short cyclone" is merely a label that could just as easily be applied to my design.  Calling the VV a "short cyclone" does not make it unique in any way.

True. I do suspect that the airspeed is higher in the Virvelvind, though, but see below.

Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
Do many people use them for woodworking?  I wonder because I haven't come across it before.

No, and I think your design might be more suitable for woodworking, with large(ish) shavings and sawdust. There is a sweet spot size like you said, and that is porbably larger in your separator. Many here use the Virvelvind to protect their vacuum cleaner when they clean out ash in their wood-pellet burner. That is why I'm so focused on small-sized dust. The down side is probably a larger pressure drop (less air flow).

Agreed.

I do understand that your construction is not a cyclone. Your construction allows the air to slow down and expand a bit, so that the debris has time to sink into the slot. This is a sound idea. But as you say, with the inlet close to the baffle, there will inevitably be some turbulence there. So the baffle needs a solid part that hinders the turbulence from influencing the air mass (and debris) below the aperture to re-enter the air flow above the baffle.

But the Virvelvind is a (short) cyclone, that tries to keep airspeed as high as possible, pressing the dust out to the outer wall. This is why a stepped construction might work without a big baffle. The inlet is, relatively speaking, far from the step (and vortex breaker). The inventor talks about airspeeds of 180 km/h (50 m/s or 110 mph) in the cyclone. I don't know about that, but the idea behind a cyclone is just that: high airspeed.

The lower part of the cyclone ("above the fill line") allows the air to slow down and expand a bit. Therefore, I was thinking that your baffle might help. But you seem to be saying no.

Anyhow, since people seem to be happy with the performance, I'll risk it and buy one. Given some time I'll experiment with it too.

Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
Definitely bigger baffles work better than smaller.  I've tested both, there is no comparison, in this case bigger is always better.

In constructions based on your principle, yes. And as I said, that principle is sound.

Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
It is a little more complicated than that.  Once debris falls below the baffle, we want it to settle and stay settled. 

Agreed, I just didn't write that.

Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
Beyond that, we want the baffle to keep anything that IS resuspended as far from the outlet port as possible.  Close to the outlet port, things get pretty chaotic, with slow-moving areas, rotation changes, etc., allowing fine dust to sneak right into the outlet stream.

Yes, and in the short cyclone, this is achieved by a tangential inlet far from the vortex breaker.

Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
I've made at least 50 separators, and I've done designs very similar to the Virvelind, it isn't an academic question, I'm speaking from experience.

So is this guy. He's not an academic, he's a hands-on inventer.

Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
The reason they have that max fill line painted on their bucket is because they need it.  Above that line, a similar design I was testing passed pretty much everything to my shop vac.  And even below that line, there was plenty of scrubbing going on.

That's because the top part of the container is part of the cyclone. Which is why I was wondering if a baffle at the bottom of that would improve things further. But as you pointed out, there is nothing like an experiment to find out.

I'm not sure it needs a big baffle.

As I understand it from your explanation here, the baffle is meant to separate the air mass above the baffle from the air mass below. This is to keep stuff from re-entering up through the aperture, and perhaps make it out the exit. I think that is a sound idea.

But there may be a good reason that separation is good in this "short cyclone" too. There is a big aperture instead, so that the air below the separator also moves, perhaps somewhat slower than the air above. And importantly, there is an outer rim to the lid at the same height as the separator (the cyclone is not as big as the lid). This means that dust that has gone below this level is forced out, and is hindered from entering the air stream above that height (perhaps not completely, but anyway). The center vortex is blocked by the disc, which this guy calls "vortex breaker" (rather than baffle), so stuff cannot be lifted in the center either. Since the two air masses move at approximately the same speed, I suspect this reduces the turbulence in the interface between the two air masses (above and below the vortex breaker), and this is a good thing. I think the principle is sound here too.

Different principles, similar end result. Now I'm wondering whether there would be a benefit to using both mechanisms in the same device. Perhaps put a baffle at a distance below the vortex breaker, with the appropriate diameter. I might try this out.

I suspect a larger radius would make it worse for the fine dust. There are larger versions, for "industrial" use, biggest tank they use is 25 cubic metres  8). Pellvac's own use is for ash and wood-pellet dust in their vacuum wood-pellet-handling system, so it is aimed for fine dust, not coarse.

They claim 99 percent for talcum powder, I'd expect larger chips to be better separated. There is a video on youtube where they use it on wood-pellet ash: 1 kg of ash through the thing, and 8 grams make it through. There is also a referece to a test at Chalmers (technical university), but I have still to see the report.

I do want to use mine for ash, so it makes a big difference if it handles fine stuff or not. I might buy one and try it out.

They do list their separation to be 99% so I'd expect some dust to make it to the bag, yes. But they claim it is efficient for fine dust too. What is the efficiency of your construct?

Hi, thanks for making the plans available to us all. I was thinking to build this for myself but found http://www.pellvac.com/s/askcyklon.php. Different, but similar. It isn't cheap, though. Apparently from the 70's, see http://www.pellvac.com/pdf/artikel%20uppfinnaren%20och%20konstrukt%f6ren.pdf. Now, to the question: The aperture is much larger in the whirlwind, and has no solid part. What difference does this make, if any?