Ducting between cyclone and collection bin

[Squarenuts]

I seem to recall somewhere reading that a longer length of hose between the cyclone and the drum could help catch a bit more of the fine dust, but I just can't find it. Thought it was in these forums, but i looked in the interwebs too and can find nothing. Anybody know what I'm talking about?

 

[Rushton]

I recall the same advice, Squarenuts, but not sure where I saw it (Pentz's website? a comment from McRabbet?). In any event, my recollection is that the comment was that making the connection a bit longer allowed turbulence to settle and improved separation. The distance discussed was not large, perhaps up to a couple of feet versus the typical six inches.

 

[jsbrow]

Squarenuts,

I cannot help with the reference you are seeking nor can I offer a recommendation (short versus long transition between the cyclone funnel and dust barrel). Generally your question suggests an effort to maximize separation, especially at the bottom of the cyclone funnel.

On one hand I have read in an article where cyclone efficiency is broadly determined by two major factors: 1) velocity of particles within the cyclone and 2) the length of time the particles spend inside the cyclone. The second factor, suggests that increasing the cyclone funnel to dust barrel distance would improve separation. (I looked for this reference but could not find it)

On the other hand there is a phenomenon called “re-entrainment”. “Re-entrainment” is where fine particles of dust that are swirling in the vortex are caught in the low pressure zone at the center of the vortex and the bottom of the cyclone funnel and thus transported to the filters. I suspect this occurs at the funnel/barrel transition due to the narrowing of the vortex. If this understanding is correct, then “re-entrainment” is more likely with a long transition between the cyclone cone and barrel.

I have little confidence that I understand the physics operating at the cyclone funnel/barrel transition. While I am aware of the vortex breaker and antilock discharge assemblies at the cyclone funnel/barrel transition, I did not incorporate the devices in my install. On my install I used a minimal length of flex hose to transition from the cyclone funnel to the barrel. This decision was driven by my desire to maximize the height and thus capacity of the dust barrel. I have no way of knowing whether my decision was a compromise in separation performance or an enhancement.

If you are further interested, here are two references which, while highly technical, offer information regarding cyclone performance:

http://cdn2.hubspot.net/hubfs/1546095/pdf/How-to-select.pdf

http://mech.vub.ac.be/thermodynamics/phd/PhD_thesis_Khairy_Elsayed.pdf
Section 2 describes cyclone types and principles and section 2.5.2 specifically address cyclone funnel/barrel geometry

Additional resource may be on Donald Torit website, but since I elected not to provide the marketing info they requested, I cannot say whether any technical information they offer is relevant to your question
https://www.donaldson.com/en-us/ind...MIqbbOg4_x2QIVwxuBCh0wLgoQEAAYASAAEgJ6_fD_BwE

 

[egbell]

Good afternoon:

jsbrow: I looked at one of your links and it is interesting. I have a question. Is a 'vortex breaking hopper' the barrel on the Clear Vue or is this something different? I ask because of the 'airlock discharge' and 'discharge' also pictured. I'm trying to get it all sorted out. I'm not considering the picture as the absolute gospel. I just have an unhealthy curiosity about stuff like this.. unhealthy only because it so often leads to second-guessing myself. I plan on reading the information you linked completely when I have more time, but this question in context of this discussion of the length of the connection between cyclone and hopper seemed more relevant and interesting because I have been thinking about this topic since I first read it, given where I am in my installation.

 

[jsbrow]

egbell,

You have reached the limit of my knowledge; I have not looked further into the vortex breaker or the airlock discharge. I am uncertain of the critical design elements of these devices. It may simply be the shape shown in the sketch. However, there may also be some interior components not discussed or shown in the diagram that are critical to their function.

The primary reason I did not look into the vortex breaker or airlock further is that even if these cyclone add-ons improve cyclone performance I did not wish to sacrifice dust/debris capacity. Adding these components would make the cyclone tower even higher than it is now unless the barrel were reduced in height.

As to you question; I do not believe the dust/debris barrel is equivalent to the vortex breaker and/or airlock discharge. When looking into the barrel while the CV1800 is running I can clearly see the vortex extending into the barrel. There is a viewing window and lighting to illuminate the interior of the barrel allowing me to monitor the contents of the barrel. My observations lead me to wonder whether the vortex action occurring in the barrel is stirring up fine dust that then enters the low pressure zone of the vortex and is sucked into the filters. Perhaps that is what the vortex breaker and/or airlock discharge is designed to prevent. I am not sure.

In a commercial or industrial setting, reducing the amount of fine dust making its way into the filters may have some cost and maintenance advantages. Since I am a hobbyist, I figure I can clean the filters more frequently than may be otherwise necessary.

I considered a barrel with square corners rather than a round barrel. However Clearvue technical support recommended against a squared container and so I went with a round container.

 

[McRabbet]

I agree with Jsbrow about the height issue and, like him, I am not familiar with the internal working of a vortex breaking device. Large industrial cyclones are often outdoor installations and they have the room for such additions. With the CV1800, the dust continues down into the bin in a spiral fashion and return air does come out up the center of the cone into the blower intake. Of note, the pile of dust in the bin is usually left in a conical form with the peak of the cone in the center; the dust swirls around the perimeter on the bin to form this shape. In addition, if the bin leaks through the top or a side seam, the conical pile may not form.