Processing using cavitation

[nigelb]

The pump is an 80lt Lowara...lovely pump it is...and the venturi is matched to it. A 9.3mm throat if I rememeber correctly.

The intersection is a sharp angle. I suppose I could round it off and see if it makes a difference.

Did you round off the intersection in your venturi Julian? Are you still on a cast one or have you moved to a machined jobbie?

[Jamesrl]

The pump is an 80lt Lowara...lovely pump it is...and the venturi is matched to it. A 9.3mm throat if I rememeber correctly.

The intersection is a sharp angle. I suppose I could round it off and see if it makes a difference.

Did you round off the intersection in your venturi Julian? Are you still on a cast one or have you moved to a machined jobbie?

As a matter of interest Nige I always take the sharp edge off at the intersection of the two cones.


Open the throat on your venturi to 9.5mm and round the edges.

One of our number used to work on the design of very fast racing cars and knows a thing or two about air and liquid flows.

Anyway he's put some info into his poota and it's spat out a new profile, not vastly different just a couple of subtle changes. I'm gona make one and see if there's any improvement on performance over one of me standard venturis.

[Julian]

The pump is an 80lt Lowara...lovely pump it is...and the venturi is matched to it. A 9.3mm throat if I rememeber correctly.

The intersection is a sharp angle. I suppose I could round it off and see if it makes a difference.

Did you round off the intersection in your venturi Julian? Are you still on a cast one or have you moved to a machined jobbie?

As a matter of interest Nige I always take the sharp edge off at the intersection of the two cones.


Open the throat on your venturi to 9.5mm and round the edges.

One of our number used to work on the design of very fast racing cars and knows a thing or two about air and liquid flows.

Anyway he's put some info into his poota and it's spat out a new profile, not vastly different just a couple of subtle changes. I'm gona make one and see if there's any improvement on performance over one of me standard venturis.

I wonder if this mystery member can come up with a devise to create cavitation?

[Julian]

The pump is an 80lt Lowara...lovely pump it is...and the venturi is matched to it. A 9.3mm throat if I rememeber correctly.

The intersection is a sharp angle. I suppose I could round it off and see if it makes a difference.

Did you round off the intersection in your venturi Julian? Are you still on a cast one or have you moved to a machined jobbie?

Still on a cast unit, but it's a four port with a separate chamber around the ports.  Still doesn't demeth as fast as I'd like ... I'm pretty sure it's pump thing.

I've started wondering if what I know as an ejector, where a jet fires across a void before entering the throat, might not be a better design ... all the serious commercial devices are made that way.

[Jamesrl]

I wonder if this mystery member can come up with a devise to create cavitation?

I'll have a word with him, his identity must remain secret though coz I'm keepin' to meself, so there.

[Jamesrl]

I've started wondering if what I know as an ejector, where a jet fires across a void before entering the throat, might not be a better design ... all the serious commercial devices are made that way.

Wonder no more, during my research period, some 7+ years ago, I play with the ejectors and got one to draw in 10ltr in 28secs using an 80ltr/min pump, that gave a 1:4 ratio.

Yes they are very efficient but getting the two diams to line up exactly can be a bit fiddly, you can vary the gap to increase the drawn volume.

Needless to say I did make a a mod or two to the receiving cone to get the 1:4.

The best standard venturi I made used the de Laval Rocket nozzle principle, the complete reverse of the aerofoil shape.

Have a go and see what happens.

[Julian]

The one with the curvy sides ... tricky to fabricate, but quite easy to cast.

Do I have a stab at yet another venturi ... hmmmm.

[Jamesrl]

Do I have a stab at yet another venturi ... hmmmm.

Of course you do, every time I have a rummage in the garage I find another prototype venturi, I got loads of'm.

[Julian]

I was rather saving the fun of making yet another venturi until I remake the processor with square tanks, dust Heather off and put her to work ... still need to work out what she's capable of.

Would quite like a stab at a cavitation device in the mean time though.

[Jamesrl]

Would quite like a stab at a cavitation device in the mean time though.

Nah, nah, nah, get Heather working a venturi to its max efficiency first, trial it on your existing plant and move on from there.

PS. I can can supply bespoke square tanks with pyramidal cones both top and bottom for the rector and open topped for anything else.

[greasemonkey]

I'm still not entirely sure i understand this. How can cavitation be induced under pressure, or by spraying?
Surely it needs something like a vacuum being created.
Wouldn't it be easier to induce cavitation by suction?

It's not just pressure, it's a sudden change of pressure which creates, not a bubble, but a void.  The void is unsustainable and collapses with the effects described above.

This explains diagrammatically ...





An easy way to create cavitation is indeed on the suction of a pump.  If you throttle a valve on the suction, most pumps will cavitate, but it doesn't do the pump much good ...



Or on a boats propeller ...

Thanks. I can see more of what is happening now. Obviously it is fairly violent.

[Julian]

PS. I can can supply bespoke square tanks with pyramidal cones both top and bottom for the rector and open topped for anything else.

PS ... so can I!

[Julian]

Nah, nah, nah, get Heather working a venturi to its max efficiency first, trail it your existing plant and move on from there.

Heather is going to need some mother big pipe work ... fitting her to my current plant would crap her style.

I've fitted a removable section of pipe work on my current plant to try different venturis and I'll probably start out by doing the same on the new one.

[photoman290]

Thanks. I can see more of what is happening now. Obviously it is fairly violent.
[/quote]

this is the  opposite of the theory used in the acetone reaction idea from a few months ago. do we want violent agitation or gentle blending of the reactants?

this paper looks interesting, and more importantly possible to make in the shed.

http://repositorium.sdum.uminho.pt/bitstream/1822/3674/1/SSChE2005-176p%5B1%5D.pdf

i was thinking plastic tubing and hose clips to pinch the tube to the right shape. if it works you could do it with 15mm to 8mm end feed reducers for a more permanent version.  put it inside a water jacket made from 40mm wastepipe to kepp the temperature correct. if you heated the oil first you should not get much temperature drop as the methoxide or ASM is going in in small amounts.

i know the theory works as i have seen bio made using a oscillatory flow reactor.

[greasemonkey]

There's summat up wiv your link, Bob.