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  1. #21
    Member peteeng's Avatar
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    Default Re: Dust collection

    Hi All - I have been struggling with the transverse velocity profile of the cyclone. I thought that the max velocity was at the cone surface. Which it isn't. The max velocity is at the interface of the inner and outside vortex. Now things make sense. The centrifugal forces push the particle outward. This means the particles are moving into a slower area and as its drag decreases it drops out of the airstream. The particle is either being sweep along in the flow and moving outward in the outer vortex (until it drops out or hits the wall) or if its in the inner vortex its gets accelerated into the outer vortex and the cycle goes on. As the particle moves down the cone the velocity drops further due to the smaller radius. Again at some height level the particle mass overcomes the drag force and it drops out. Can let my brain have a rest now.... Peter

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  2. #22
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    Default Re: Dust collection

    Quote Originally Posted by peteeng View Post
    Hi All - I have been struggling with the transverse velocity profile of the cyclone. I thought that the max velocity was at the cone surface. Which it isn't. The max velocity is at the interface of the inner and outside vortex. Now things make sense. The centrifugal forces push the particle outward. This means the particles are moving into a slower area and as its drag decreases it drops out of the airstream. The particle is either being sweep along in the flow and moving outward in the outer vortex (until it drops out or hits the wall) or if its in the inner vortex its gets accelerated into the outer vortex and the cycle goes on. As the particle moves down the cone the velocity drops further due to the smaller radius. Again at some height level the particle mass overcomes the drag force and it drops out. Can let my brain have a rest now.... Peter
    What many overlook is what happens just below the inversion point, I have more tests to do but I believe a neutral pressure cell is created similar to that of the Eye of a Cyclone that facilitates the separation process, I feel there has to be a way to control the inversion point so it only occurs at the very base of the Cone.
    This could be by using a VFD controlled Fan or
    Having a parallel bank of smaller Cyclones where individual Cyclones can be enable or
    Disabled or controlling an adjustable inlet and outlet aperture of the Cyclone.
    Or drawing air lowering air pressure from the particle receptacle to lower the Cyclone if it inverts to high in the chamber.. this just came to me.

    I am no professor or mathematician but Cyclonic Practical Separation has had me fascinated for some 2 years now.
    It has frustrated me to no end how many company engineers have posted misleading erroneous papers and videos on how their Cyclonic Separators work.
    I just feel most people who have published papers and videos have limited them selves to the foundation principles started from 1985.

    I feel there is a lot more to be done with cascading and introduction of other technologies to compact the footprint and improve efficiency.
    I am currently working on some design for a vertical panel of miniature cyclones to eliminate or dramatically increase the time between maintenance of exhaust cartridge filters.

    I hope to also have a small self cleaning dust extractor that can sit behind the Z Axis or on the side of the Y Axis of a router with minimal noise and separation efficiency of HEPA filters down to .3 - .5µm

    This is why I like to engage people in discussion to challenge me and me them, helps me learn.
    For now ill take a look at that Cyclone Thesis.

    Maybe Admin could add a Dust extractor separator area to the forum



  3. #23
    Member peteeng's Avatar
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    Default Re: Dust collection

    Hi Decoy- Unfortunately this sort of process can't be solved from first principles due to its complexity. The thesis spells out all the assumptions made in the maths to make the problem solvable. Then tests are done and the theory is calibrated to the tests. That's good enough in practice. I expect a very good answer can be found these days with CFD. Vorticity and particles in liquid flow are very well modelled these days. So maybe do a search for work done by some of the FE companies altair, ansys, lusas etc. Someone probably has had a crack at it. Good luck in your endeavors

    Have a look at air-conditioning filters as well and cooktop filters. They have channels that create impinging air flows to slow the flow and allow the particle to drop out...Peter



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    Default Re: Dust collection

    Quote Originally Posted by PeteJW View Post
    I've just purchased a hobby CNC machine and attempted to surface the spoilboard (MDF) obviously loads of dust and so a face mask. Whilst the surfacing was going in I held a 1200watt domestic vacuum near to the cutter to remove the dust but its still going everywhere.
    I assume a dust shoe would help contain the dust, but are there any advantages to using a shop vac rather than a domestic vacuum
    Initially I bought a cheap, 2000W domestic vac, but while that made a huge noise and consumed all the 2kW, it was worthless as a vac, so I returned it to the shop. All domestic vacuum cleaners are not the same... Now I have a Made in Germany, Miele 2100W and that has no issues at all. Of course, I also have a shoe which follows automatically and closes in the cutter, so yes, that makes a HUGE difference when collecting dust. The problem of domestic vac is that the bag is too small, but for my needs (mostly PCB and plastics) it lasts forever. So, it all depends on how much dust/chips you need to collect. Nevertheless, I think a 1200W domestic vac is at the low end, even though, if it is quality and efficient, it could indeed do a good work, but if you are serious and will use your machine day in and day out then a real shop vac is necessary, but beware, they are also different in efficiency and quality, so usually, you get what you pay for, it's not just about the label stating the watts, but also the name, and generally the price.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: Dust collection

    Quote Originally Posted by PeteJW View Post
    Just found out how to upload photos. This is what I have at the moment
    Attachment 464889
    Attachment 464891
    Try again, because it did not work. Pictures are not shown.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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