May 11, 2019
Description
"Axial fans are good at moving high volumes of air at a low pressure. One problem with a ducted axial fan though, is the big negative pressure vortex behind where the hub, or motor is. Filling that volume with a cone really smooths out the air flow inside the duct. Another issue with axial fans is efficiency drops as back-pressure increase more rapidly than it does with radial fans. What happens is that the air starts to spin around with the fan blades. If it's spinning around with the blades, it's not being pushed along the axis of the fan. To visualize this property, imagine if you blocked off both sides of the fan by laying anything flat like card stock and turned it on. In this case you have zero flow, and what air is trapped between each blade will just spin around inside the fan housing with the blades. Placing some fins in the duct behind the fans helps reduce the amount that the air swirls inside the duct. I tested out the first one in the pictures and the air flow really seems to have improved dramatically. Afterwards I thought about increasing the size of the fins but have not yet printed it. Now, my anecdotal evidence is pretty meaningless. Lord Kelvin said it best, "I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind." So, I've looked and looked but I can not find a simple (i.e. cheap) way to actually measure air flow. If anyone out there can do that and provide some comparative numbers it'd be greatly appreciated. I tore a small piece of paper and held it over and under the fan, with and without this "inator", and can definitely see a difference. I would love to be able to assign some actual cfm numbers to it. I have included four versions. I have two different fans on my printer. A decent Sunon fan with an 18mm hub, and some budget fans with 24mm hubs. For each hub size I have one with small fins and one with large fins. I have tested the 24mm, short fin version."I'm still tinkering around with a method to be able to measure the air flow through the system. I'm consider making an venturi to, and attaching a simple manometer. As the cfm goes up, so should the pressure drop through the manometer. That alone would be a useful data point to compare air flow improvements, but maybe there's a way to convert that value to a cfm. As I forgot to mention in the last thing, I have two brands of fans, one has a 24mm hub, the other has an 18mm hub. If you have a fan with a different diamter hub, post a comment and I'll do my best to get another statorinator uploaded that'll work with your fan. And finally, my fans spin counter-clockwise as viewed from the top (inlet) side. If your fans spin the opposite direction, mirror the parts in your slicer. I have no idea if fan spin direction is an industry standard thing or not.
License:
GNU - GPL
15,655
Madau3D
