[titus]

Hello guys,

Well the cons for air driven skimmers are size, difficulty of adjustments, and power consumption. However, I believe given the proper equipment, a patience to adjust it properly, air driven skimmers can out perform Becketts or ETSS.

And yes I was thinking about the piston type air pumps. Not those ones you plug into the wall with. [img]images/smiles/icon_biggrin.gif[/img]

There are a few reasons why I came to this conclusion. When I still used to build skimmers, I paid very close attention to the surface turbulence of Beckett skimmers, and non-Beckett skimmers. I found that Beckett requires a very high flow rate to achieve a good bubble density. This high flow rate unfortunately results in a higher surface turbulence.

This turbulence is caused by 2 factors:
1) Most high aeration skimmers are feed offset. This mean the air/water mix is fed next to the riser column. And some bubbles accumulate in size by trapping at the top plate. When these bubbles finally move over to the riser column, they rise up too fast because of its size.

2) Further because the feed is offset, you always see one side of the riser column causing a compromise when adjusting air intake. In the case of the PM Bullet 2, bubbles with larger size rises faster and more violently on the side where the Bullet injector is.

Note that if the feed can be brought directly to the center of the riser column then the above 2 problems should go away when properly designed.

Finally, there is a problem with bubbles returned. Because of the compactness of these skimmers and the use of a vertical baffle, large amount of bubbles are being returned. So there really isn't much counter current action as most of the bubbles that go downward towards the drain actually got drained out of the skimmer.

Solution?
1) Do what the Aerofoamer does by injecting directly into the riser column. This solve all 3 of the above problems. And add a nice counter current action.

2) Do what I used to do with the CS-2 horizontal baffle. This solve also all 3 of the above problems. The also add a very nice counter current action. This happens when the water turns 180 degree around, right below the riser column.

I think the more I iterate the design, or the more I think about it, the Aerofoamer approach of feeding directly into the riser column is the way to go. However, I know of a different point in the riser column where I can feed to give better counter current action.

Titus