I'm building a new processor to bring together all the advantages of the GL 1 day process.

It is a closed-system fume-free processor which removes the need for water washing, reduces pollution, eliminates emulsions, recovers methanol which would otherwise have been washed down the drain, and reduces oxidation by working with a limited volume of air, or if preferred, inert gas such as CO2 or Nitrogen.

Anyway, a key component in this processor is a vacuum venturi. The processor uses 2 of these.

I've spent a fair amount of time getting the vacuum venturi part right, so thought it may be of general interest. The venturis I've come across commercially aren't ideal for our plumbing or our chemicals.

This one is well suited because it uses standard plumbing parts. And that means cheap, too.

It is handy for dosing the methanol, because you can have the methoxide tank low down in the system - no need to rely on gravity alone.

I have placed the venturi in the outlet of the pump. (I know, I can hear the groans of disapproval now!). This gives excellent mixing, however, and I get good conversion. The advantage of having the meth feed on the outlet of the pump is that the pump doesn't cavitate any more if air is drawn in, or if the methanol vapourises under the reduced pressure on the inlet of the pump. The venturi seems to mix well, of its own accord.

Here's the venturi description.

I should have the new processor plans ready to publish in the next week or so. Still a few bugs to iron out.

This message has been edited. Last edited by: GrahamLaming,

Graham;
I don't know or understand the first thing about this but it looks brilliant.
If you ever get over to this side of the pond we'll have to hook up over a pint.

Hey Graham,
Thats a very clever way to make a venturi! Simple, cheap, no machine tools. My sincere compliments.

Chris

Brilliant work yet again Graham! Thanks for sharing.

Nick

Graham,

That's a great way to make a venturi! Do you have a needle valve on it?

Keep those briliant ideas flowing Sir Graham!

Pretty slick there.

Home engineering things like that is almost as much art as it is science.

Have you measured or estimated its performance?

Excellent design! Nice and simple, easy to follow, and even fairly elegant in its simplicity.

What kind of flow rate was this designed to accomodate/best work with? Think they would work with some backpressure on the pump, like say connected to a static mixer?

Excellent work Graham!

Yes, all of those previous superlatives apply.

Simple
Elegant
Effective
Well thought out
Imaginative use of commom materials
Fantastic instructions and illustrations

Please carry on.

troy

Hi Folks,

I wouldn't go so far as to say it's excellent - it is far from efficient, and needs a fair through flow to get vacuum going, but it is a start and can certainly be refined for better performance.

Its biggest weakness is its abrupt change in diameter. It is very short. Make the bevel in and out as smooth as you can.

Really it should be a very gradual, smooth narrowing to the inlet, and a gradual, smooth narrowing to the outlet.

Ensure the flow into it comes from a fairly straight run of pipe - don't mount it just before an elbow, that seems to affect it - probably turbulence. And don't have any air bubbles flowing in the upstream end (inlet) - that seems to upset its performance too.

Being so short, it probably wastes a lot of power creating turbulence downstream. That's probably why it mixes the methanol in quite well.

If anyone can figure out a way to get around a 10 degree taper on the inlet and outlet, it would work much better.

I've been whittling away at some dowel rods to make 10 degree tapered spears - I plan to jam a spear into a section of copper pipe and pour solder in to create the taper. I think that should transform the performance.

Hi Graham

You say in your first message that the venturi produces sufficient vacuum to draw methanol from the carboy. We know that slower is better when feeding in the meth and if you are correct about the turbulance, that's a good thing, no?. I'm not going to steal your thunder by revealing how you are going to use the other venturi but there too, we are only looking for a small vacuum aren't we?

Regarding the taper, how about filling up the fitting with solder completely and using a spearpoint bit such as is used to drill glass and ceramic tiles? They have a tapered profile and should cope with soft solder ok.

Cheers

Nick

Hi Nick,

Do you know what diameter they go up to? I'm not familiar with those at all, but a fine taper drill with 20mm final diameter would be good.

I recon the taper needs to be around 70mm long for best efficiency, going from 20mm diameter down to 12mm diameter.

That seems to make it a lot less sensitive to what is upstream or downstream of the venturi.

I'm using plasticine to fashion the taper , using a length of 10mm dowel to make it conical down the tube - keeping one end still (the narrow end) and moving the other end around to displace the plasticine into a hollow cone inside the tube, which is 75mm long.

Not very BD resistant, but my 8 year old son and I are testing it by pumping water around a bucket, through a 10 foot length of 22mm pipe, using a grundfos pump. It is FREEZING cold outside, so the plasticine is pretty much solid. We've had enough, come in for a hot cuppa.

But yes, even as it stands, it does the job reasonably well, especially for the vapour recirculation.

Try a #1 or #2 Morse Taper hand finishing reamer.
#1 0.5170" to 0.3674" in 3"
#2 0.7444" to 0.5696" in 3.5"

Spiral flute taper reamers should also work. There are many sizes available.

You can also use a 1 X 3/4 X 3/4 tee and put a piece of steel pipe cut at a 45° angle in the branch. The large opening goes to the pump inlet, as does the opening in the steel pipe.

Hi Graham

I can't find a spear point drill larger than 13mm so that's no good. I think agroot is right - a tapered reamer is the way to go. This one is the right size I think. Also consider this hand reamer

Cheers

Nick

Go with a hand reamer, as the solder is a very soft material. You can use a piece of pipe as a collar to limit the insertion, and keep it centered.

Many thanks for those suggestions - they look ideal.

I've found another way to generate suction from fluid flow, which I've started to build into the same style of Tee fitting. Should be similarly easy to achieve with average home tools, and I suspect may be more suited to the methoxide injection task, than the venturi.

I'll compare performance of the two systems over the next week or so and post what I find.

Don't know if it's the right taper or the right size but woodworkers use a pointed tapered drill for screw holes in various sies from #4 to #10. Or grind your own using a worn out drill bit with a drill and grinder.

quote:

Originally posted by Twenty4Seven:
Hi Graham

I can't find a spear point drill larger than 13mm so that's no good. I think agroot is right - a tapered reamer is the way to go. This one is the right size I think. Also consider this hand reamer

Cheers

Nick

I had a thought (it happens). What if you were to take a piece of cold roll and drill a tappered hole into the end in the diameter that is required and use that as a sleave inside the pipe? Do the same for the other side. There's got to be a drill bit that can tapper right ? I got drill files that taper so there's got to be a bit out there. My 1/2 pennie's worth :-)

Chuckle chuckle...

You're a better DIY'er than I, if you can make this with hand tools and a drill press in CRS.

I'd recommend doing it on a lathe. If you don't have access, give the job to a machine shop.

Does anyone have or know where the "rule of thumb" guidelines for venturi design are available? For example if you want "such & such" vacuum at "such & such" flow what size diameter orifices are required. You know, engineering design parameters?

From Wikipedia:
"Venturi Tubes
The simplest apparatus, is a tubular setup known as a Venturi tube or simply a venturi. Fluid flows through a length of pipe of varying diameter. To avoid undue drag, a venturi tube typically has an entry cone of 30 degrees and an exit cone of 5 degrees.
A venturi can also be used to mix a fluid with air. If a pump forces the fluid through a tube connected to a system consisting of a venturi to increase the water speed (the diameter decreases), a short piece of tube with a small hole in it, and last a venturi that decreases speed (so the pipe gets wider again), air will be sucked in through the small hole because of changes in pressure. At the end of the system, a mixture of fluid and air will appear.
Orifice plate
Venturi tubes are more expensive to construct than a simple orifice plate which uses the same principle as a tubular scheme, but the orifice plate causes significantly more permanent energy loss and is less accurate."

The diagrams from Graham would be more along the lines of a orifice plate. HTH