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Unread 10/03/2008, 05:55 AM   #1
tarzan
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Annular venturi - "Pimped Beckett" - gathering ideas

Since the discussion in LFP Super Venturi thread got a little "wider" (out of track actually) I decided to post a new thread in hope that it will continue here.

My thinking is just theoretical, based on my estimations and work done by researchers in 1990 (yeah, not that near past) here's the document (link originally posted by BeanAnimal). It's actually the same conversion used as in Venturi -> Becket and LFS -> Annular venturi (let's call it AV).

So, first a rough sketch of a Beckett head (i used a bad pic to draw over it - so it is not really precise):


As JoelNB said, an impedance transformation is best approached with an exponential expansion. Cone is a good approximation but is less efficient, and throat expansion is more critical than the mouth contour. Also BeanAnimal added, that less laminar the flow, the more it separates and the less gas is educted, so the flow efficiency is dictated by the shape of the ports. The sketches posted here show the cross section changes of conical Venturi and LFS venturi.

So the idea (as was suggested by Hahnmeister) now is to get that LFP done as Annular venturi and to be able to swap the inserts that would look like a 'cartoon missile'. Here's the first sketch:


Suggestions of how to fabricate this are welcome, also the place of holders of that cartoon missile, number of holders (on both or just on one side), what could be adjustable etc.


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Unread 10/21/2008, 03:45 AM   #2
tarzan
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OK, since nobody is really interested i am now proposing a new way of using this kind of venturies.

As I suggested to YF in his exciting thread and daleKW in his pump mod thread maybe this kind of venturi is just best for air introduction on pump inlets side when the pump used has a bearing. What I'm talking about is an asperating venturi that utilizes the Annular venturi shape. It could be just an insert, that you would just be attached on the pumps volute part that holds the axle of pumps rotor. Here's a quick sketch:



So, what do you think? Would it be perfect or not?


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Unread 10/21/2008, 06:02 AM   #3
EnderG60
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seems like it could work. bust out a hunk of wax and see.


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Unread 10/21/2008, 06:54 AM   #4
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I am just giving the idea out, i am not much of a DIY-er, due to my wife not understanding that obsession of mine... She just can't stand me always cutting some bits of plastics and acrylics because of the mess i leave behind. So i am just thinking and dreaming how it would be if ...

Good luck with all the attempts you guys will do! Maybe some day she will give me some time off and I will be able to play with it a little too.


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Unread 10/21/2008, 08:34 AM   #5
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You might want to angle the air inlet holes so that the higher pressure water doesn't shoot out of the sides.


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Unread 10/21/2008, 10:10 AM   #6
tarzan
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True, that's the same as was suggested by Liveforphisics for his LFP venturi and JoelNB sketched in this post in that thread.


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Current Tank Info: 11g AIO Lps-sps-softy tank hosting 1 clownfish, 1 anemone QC and 3 sexy shrimps. Diy Dulux-s lightning, DIY lexan surface skimmer, DIY digital temp. reg. (w 12V vent.), ground probe (connected to DIY power wrack with 10mA Diff.) and DIY ATO
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Unread 10/21/2008, 01:40 PM   #7
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@Tarzan...
a inject-nozzle vs. Needlewheel-nozzle, is a completly different Story. Your Sketch is a nice idea for inject-nozzles, or not for Needlewheels or Meshwheels. The waterinjection for Needle/meshwheels of your sektch is to small...

best regards... Klaus


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Unread 10/21/2008, 03:01 PM   #8
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I agree with Klaus... great for a pressure pump w/ venturi on the outlet, but not a needlewheel/asperating pump where the venturi is on the intake. You want to keep the inlet as close to the center of the pump's intake (where the suction is greatest). When you start pushing the inlet to the outside diameter of the pump, you lose suction (and gain pressure). Part of that is most likely based on the scale of your drawing though... it COULD workif you can push the OD of the inlet pipe back together to be smaller... in which case, you are back to a regular venturi...lol.

There is also little point to an annular body venturi on an asperating skimmer. What innovations there are to make needlewheels better have to do with the impeller well/volute as well as impeller... not the venturi, since the maximum potential for a needlewheel is determined by these parts, not the venturi so much. If a needlewheel and impeller well only allow for 2000lph of air, for instance, before too much air causes the pump to lose suction, then the putting a better venturi isnt going to do anything.


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Unread 10/21/2008, 03:47 PM   #9
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Quote:
Originally posted by Klaus Jansen
@Tarzan...
a inject-nozzle vs. Needlewheel-nozzle, is a completly different Story. Your Sketch is a nice idea for inject-nozzles, or not for Needlewheels or Meshwheels. The waterinjection for Needle/meshwheels of your sektch is to small...

best regards... Klaus
Why not enlarge the whole thing then to 2" ? keeping the same water gap size.


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Unread 10/21/2008, 03:56 PM   #10
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Last edited by BlueCorn; 10/23/2008 at 07:39 PM.
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Unread 10/21/2008, 03:58 PM   #11
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You want a full opening to allow as much water in as possible. Blocking the inlet as shown in the diagram would stave the pump quickly. The "venturi" in a needle wheel pump is really a misnomer. All it is really doing is adding large bubbles to the water stream. Yes, the venturi effect is what is pulling the water in, but it is not the same as a Beckett head. A Mazzei injector and Beckett head require significant water pressure to create the foam. A needle wheel/mesh wheel creates the foam. These are two separate and incompatible techniques to creating foam.



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Unread 10/21/2008, 05:17 PM   #12
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I honestly think that the "thingy in the middle of the venturi" just complicates matters. It requires support, and I can t see any benefit over the standard venturi as LFP has shown other than providing more area for intake air holes.

I think Luke (LFP) has the perfect setup. Just experiment as he has shown and you cant beat that.

Stu


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Unread 10/21/2008, 05:39 PM   #13
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Because of how it works, you dont even need a 'funnel shape' on the inlet of the pump for a needlewheel.... just a straight/flat opening, as short as possible is all you need since you are taking water from a static body of water.


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Unread 10/21/2008, 05:41 PM   #14
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Now on the outlet end of a pump, that style of venturi is something to think about... and why I brought it up in that other thread.


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Unread 10/22/2008, 02:59 AM   #15
tarzan
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Thank you all (but Lord Viper )!

I haven't consider all the facts. Stugray, the problem with the pumps with bearing is that the "thingy in the middle of the venturi" is there, you need it to hold your rotor. Thats why I came up with the new idea also considering this:
Quote:
Originally posted by hahnmeister
Because of how it works, you dont even need a 'funnel shape' on the inlet of the pump for a needlewheel.... just a straight/flat opening, as short as possible is all you need since you are taking water from a static body of water.
I left just a small cone on the bearing holder just so it minimizes the turbulence around it. Since there IS flow (don't really understand how you can say it's static body if the pump is pulling water), i think it would be helpful to maximize performance. But Hahn you were right - we're back to asperating venturi most of the asperating pumps use



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Unread 10/22/2008, 07:41 AM   #16
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The body of water in the sump is considered static... sure, it might be moving a bit, but compared to the velocity its going to get to in the pump, its rather static. So you can chop off everything up to the actual restriction point of the venturi itself... no need to contour the inlet with a cone/funnel/etc... just the restriction & air inlet at that point. There is something to be said for how far from the impeller well/impeller head that this venturi can be though. Sometimes you can be too close, or too far with the venturi from the pump intake.


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Unread 10/22/2008, 09:12 AM   #17
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Quote:
Originally posted by hahnmeister
The body of water in the sump is considered static... sure, it might be moving a bit, but compared to the velocity its going to get to in the pump, its rather static. So you can chop off everything up to the actual restriction point of the venturi itself... no need to contour the inlet with a cone/funnel/etc...
Huh? The shape of the restriction dictates the efficiency of the venturi effect. What you said is not correct.

On the other hand, if you are saying that the displacement (suction) from the pump is what is pulling in the air then the restruction is akin to a valve and the air intake an aspirator.

So are we talking about a venturi pulling in air, or are we talking about a displacement volume pulling in whatever it can get ahold of?


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Unread 10/22/2008, 11:15 AM   #18
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So let me get this straight... you dont understand what I said exactly, but its wrong?

The shape, contouring, etc... of the venturi on an asperating skimmer is meaningless. All that matters is the cross sectional area of the restriction point itself, and the interface of air. Its not as if by making the inlet venturi look more 'contoured' you will end up pulling more air or water into the pump than what is dictated by the pump's wet-end. The idea is that you aren't trying to condense the flow with the contours to try to minimize the back pressure or anything (like a regular venturi with the pump flowing into it)... its a passive system at the intake. The venturi is drawing water in from a relatively static body of water... no flow/pressure (Kinetic Energy) to conserve because there is none.


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Unread 10/22/2008, 11:58 AM   #19
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OK Hahn, but what about the new to comme ATB HOB skimmer? It sucs watter trough a pipe that's in the tank. Isn't that a good enough application for that kind of venturi (you know best since you were envolved in it's design).



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Unread 10/22/2008, 12:11 PM   #20
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Quote:
Originally posted by hahnmeister
So let me get this straight... you dont understand what I said exactly, but its wrong?
No, the huh? Was an outburst... I fully understood what you said and do not agree in the slightest

Quote:
The shape, contouring, etc... of the venturi on an asperating skimmer is meaningless. All that matters is the cross sectional area of the restriction point itself, and the interface of air.
Flow and pressure are directly related. It does not matter if the "flow" is pushed or "sucked" it is flow. You are thinking in one dimension Jon

Lets ignore that for a moment...

Your contention is that the displacement of the pump creates suction. That suction will pull whatever it can in. That means that the whole idea of a venturi is pointless on the intake. One could use a VALVE on the water intake and then a TEE with an airline of the desired size. The further the valve is close, the more air and less water is introduced. The further the valve is opened, the more water and less air is introduced.


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Unread 10/22/2008, 03:34 PM   #21
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This will work for needle wheels. I have tried the smaller version and it worked great but cht down some scfh, in exchange I got much smaller bubbles.
http://i497.photobucket.com/albums/r...nsk/img019.jpg


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Unread 10/22/2008, 03:34 PM   #22
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Unread 10/22/2008, 03:37 PM   #23
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Quote:
Originally posted by hahnmeister
So let me get this straight... you dont understand what I said exactly, but its wrong?

The shape, contouring, etc... of the venturi on an asperating skimmer is meaningless. All that matters is the cross sectional area of the restriction point itself, and the interface of air. Its not as if by making the inlet venturi look more 'contoured' you will end up pulling more air or water into the pump than what is dictated by the pump's wet-end. The idea is that you aren't trying to condense the flow with the contours to try to minimize the back pressure or anything (like a regular venturi with the pump flowing into it)... its a passive system at the intake. The venturi is drawing water in from a relatively static body of water... no flow/pressure (Kinetic Energy) to conserve because there is none.
Could you please use more simple terms.....we dont have a bachelor in skimming. Thanks.


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Unread 10/22/2008, 03:39 PM   #24
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Quote:
Originally posted by MarkS
You want a full opening to allow as much water in as possible.
Wrong ! I tried this and it slows the rotation of the wheel.


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Unread 10/22/2008, 03:40 PM   #25
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Quote:
Originally posted by Klaus Jansen
@Tarzan...
a inject-nozzle vs. Needlewheel-nozzle, is a completly different Story. Your Sketch is a nice idea for inject-nozzles, or not for Needlewheels or Meshwheels. The waterinjection for Needle/meshwheels of your sektch is to small...

best regards... Klaus
I agree, thats why I enlarged it to a 2"


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